Structured log messages with a message registry

Currently there is little structure in the log messages, making
difficult to use them for the following use cases:

- A user looking for help about a log message: the user probably
  uses a search engine, thus the results will depend on the proper
  indexing of our documentation and the various forums. It relies
  only on the wording of the message, which may change with time.
- A user wants to filter the logs resulting of the use of one of the
  components of xkbcommon. A typical example would be testing
  xkeyboard-config against libxkbcommon. It requires the use of a
  pattern (simple words detection or regex). The issue is that the
  pattern may become silently out-of-sync with xkbcommon.

A common practice (e.g. in compilers) is to assign unique error codes
to reference theses messages, along with an error index for
documentation.

Thus this commit implements the following features:

- Create a message registry (message-registry.yaml) that defines the
  log messages produced by xkbcommon. This is a simple YAML file that
  provides, for each message:

  - A unique numeric code as a short identifier. It is used in the
    output message and thus can be easily be filtered to spot errors
    or searched in the internet. It must not change: if the
    semantics of message changes, it is better to introduce a new
    message for clarity.
  - A unique text identifier, meant for two uses:

    1. Generate constants dealing with log information in our code
       base.
    2. Generate human-friendly names for the documentation.

  - A type: currently warning or error. Used to prefix the constants
    (see hereinabove) and for basic classification in documentation.
  - A short description, used as concise and mandatory documentation.
  - An optionnal detailed description.
  - Optional examples, intended to help the user to fix issues
    themself.
  - Version of xkbcommon it was added. For old entries this often
    unknown, so they will default to 1.0.0.
  - Version of xkbcommon it was removed (optional)

  No entry should ever be deleted from this index, even if the message
  is not used anymore: it ensures we have unique identifiers along the
  history of xkbcommon, and that users can refer to the documentation
  even for older versions.

- Add the script update-message-registry.py to generate the following
  files:

  - messages.h: message code enumeration for the messages currently
    used in the code base. Currently a private API.
  - message.registry.md: the error index documentation page.

- Modify the logging functions to use structured messages. This is a
  work in progress.

doc/cool-uris.yaml

@@ -7,6 +7,7 @@ dir_63ce773eee1f9b680e6e312b48cc99ca.html: []
 dir_891596f32582d3133e8915e72908625f.html: []
 dir_d44c64559bbebec7f509842c48db8b23.html: []
 dir_e68e8157741866f444e17edd764ebbae.html: []
+error-index.html: []
 files.html: []
 functions.html: []
 functions_func.html: []

doc/doxygen-extra.css

@@ -31,3 +31,31 @@ a[href^="https://"]::after
     background-size: contain;
     display: inline-block;
 }
+
+/*******************************************************************************
+ * Error index
+ ******************************************************************************/
+
+div.example-container {
+    display: flex;
+    flex-flow: row wrap;
+    justify-content: space-between;
+    gap: 1em;
+}
+
+div.example {
+    flex-grow: 1;
+    overflow-x: auto;
+    margin-top: 1em;
+}
+
+div.example-inner {
+    height: 100%;
+    display: flex;
+    flex-direction: column;
+}
+
+div.example-title {
+    padding: 0 0 1em 0;
+    font-style: italic;
+}

doc/message-registry.md

@@ -0,0 +1,293 @@
+# Error index {#error-index}
+
+<!--
+NOTE: This file has been generated automatically by “update-message-registry.py”.
+      Do not edit manually!
+-->
+
+This page lists the warnings and errors generated by xkbcommon.
+There are currently 20 entries.
+
+@todo The documentation of the log messages is a work in progress.
+
+## Index
+
+| Code      | Identifier                   | Description | Type |
+| --------- | ---------------------------- | ----------- | ---- |
+| [XKB-034] | `malformed-number-literal` | Warn on malformed number literals | Error |
+| [XKB-060] | `unsupported-modifier-mask` | Warn on unsupported modifier mask | Error |
+| [XKB-107] | `unrecognized-keysym` | Warn on unrecognized keysyms | Warning |
+| [XKB-183] | `cannot-infer-key-type` | Warn if no key type can be inferred | Warning |
+| [XKB-237] | `unsupported-group-index` | Warn when a group index is not supported | Error |
+| [XKB-286] | `undefined-key-type` | Warn if using an undefined key type | Warning |
+| [XKB-305] | `non-base-group-name` | Warn if a group name was defined for group other than the first one | Warning |
+| [XKB-312] | `unsupported-shift-level` | Warn when a shift level is not supported | Error |
+| [XKB-461] | `conflicting-key-symbol` | Warn if there are conflicting keysyms while merging keys | Warning |
+| [XKB-516] | `extra-symbols-ignored` | <span class="todo">TODO:</span> add description | Warning |
+| [XKB-578] | `wrong-field-type` | Warn when a field has not the expected type | Error |
+| [XKB-645] | `unknown-char-escape-sequence` | Warn on unknown escape sequence in string literal | Warning |
+| [XKB-700] | `multiple-groups-at-once` | Warn if a key defines multiple groups at once | Warning |
+| [XKB-769] | `invalid-syntax` | The syntax is invalid and the file cannot be parsed | Error |
+| [XKB-770] | `undefined-keycode` | <span class="todo">TODO:</span> add description | Warning |
+| [XKB-800] | `conflicting-modmap` | Warn if there are conflicting modmap definitions | Warning |
+| [XKB-883] | `conflicting-key-action` | Warn if there are conflicting actions while merging keys | Warning |
+| [XKB-893] | `conflicting-key-type` | Warn if there are conflicting key types while merging groups | Warning |
+| [XKB-935] | `conflicting-key-fields` | Warn if there are conflicting fields while merging keys | Warning |
+| [XKB-965] | `unresolved-keymap-symbol` | Warn if using a symbol not defined in the keymap | Warning |
+
+## Details
+
+### XKB-034 – Malformed number literal {#XKB-034}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Error</dd>
+  <dt>Summary</dt><dd>Warn on malformed number literals</dd>
+</dl>
+
+xkbcommon can parse the following number literal formats:
+
+- *decimal integer:* 1, 123, etc.
+- *decimal floating-point number:* 1.23, etc.
+- *hexadecimal integer:* prefixed with “0x”: 0x123, 0xff, 0xAB, etc.
+
+
+### XKB-060 – Unsupported modifier mask {#XKB-060}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Error</dd>
+  <dt>Summary</dt><dd>Warn on unsupported modifier mask</dd>
+</dl>
+
+### XKB-107 – Unrecognized keysym {#XKB-107}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn on unrecognized keysyms</dd>
+</dl>
+
+xkbcommon replaces keysyms it does not recognize by the keysym `NoSymbol`.
+
+You may find the list of supported keysyms in
+`include/xkbcommon/xkbcommon-keysyms.h`.
+
+
+#### Examples
+
+<details>
+  <summary>Unrecognized keysym “`coma`”</summary>
+
+**Error message:**
+
+```
+xkbcommon: WARNING: [XKB-107] de:31:20: unrecognized keysym "coma"
+```
+
+xkbcommon does not recognize the keysym “`coma`”. It is most probably
+a typo for “<code>com<em>m</em>a</code>”.
+See: `XKB_KEY_comma` in `include/xkbcommon/xkbcommon-keysyms.h`.
+
+**Fix:**
+  <div class="example-container">
+    <div class="example">
+      <div class="example-inner">
+        <div class="example-title">Before</div>
+```c
+key <AB08> {[ coma, semicolon, periodcentered, multiply ]};
+```
+</div>
+    </div>
+    <div class="example">
+      <div class="example-inner">
+        <div class="example-title">After</div>
+```c
+key <AB08> {[ comma, semicolon, periodcentered, multiply ]};
+```
+</div>
+    </div>
+  </div>
+</details>
+
+### XKB-183 – Cannot infer key type {#XKB-183}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if no key type can be inferred</dd>
+</dl>
+
+### XKB-237 – Unsupported group index {#XKB-237}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Error</dd>
+  <dt>Summary</dt><dd>Warn when a group index is not supported</dd>
+</dl>
+
+xkbcommon supports group index in the range (1..4).
+
+
+### XKB-286 – Undefined key type {#XKB-286}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if using an undefined key type</dd>
+</dl>
+
+### XKB-305 – Non base group name {#XKB-305}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if a group name was defined for group other than the first one</dd>
+</dl>
+
+### XKB-312 – Unsupported shift level {#XKB-312}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Error</dd>
+  <dt>Summary</dt><dd>Warn when a shift level is not supported</dd>
+</dl>
+
+Shift levels are _one_-indexed. xkbcommon supports two formats of shift levels:
+as numbers and as identifiers `LevelN`, where `N` is in the range (1..8).
+
+
+### XKB-461 – Conflicting key symbol {#XKB-461}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if there are conflicting keysyms while merging keys</dd>
+</dl>
+
+### XKB-516 – Extra symbols ignored {#XKB-516}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd><span class="todo">TODO:</span> add description</dd>
+</dl>
+
+### XKB-578 – Wrong field type {#XKB-578}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Error</dd>
+  <dt>Summary</dt><dd>Warn when a field has not the expected type</dd>
+</dl>
+
+### XKB-645 – Unknown char escape sequence {#XKB-645}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn on unknown escape sequence in string literal</dd>
+</dl>
+
+xkbcommon support the following escape sequences in string literals:
+
+| Escape sequence | Corresponding character             |
+| --------------- | ----------------------------------- |
+| `\b`            | `U+0008` Backspace                  |
+| `\t`            | `U+0009` Character tabulation       |
+| `\n`            | `U+000A` Line feed                  |
+| `\v`            | `U+000B` Vertical tabulation        |
+| `\f`            | `U+000C` Form feed                  |
+| `\r`            | `U+000D` Carriage return            |
+| `\e`            | `U+001B` Escape                     |
+| `\\`            | `U+005C` Backslash                  |
+| `\NNN`          | _Octal_ escape, from `\0` to `\777` |
+
+
+### XKB-700 – Multiple groups at once {#XKB-700}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if a key defines multiple groups at once</dd>
+</dl>
+
+### XKB-769 – Invalid syntax {#XKB-769}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Error</dd>
+  <dt>Summary</dt><dd>The syntax is invalid and the file cannot be parsed</dd>
+</dl>
+
+### XKB-770 – Undefined keycode {#XKB-770}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd><span class="todo">TODO:</span> add description</dd>
+</dl>
+
+### XKB-800 – Conflicting modmap {#XKB-800}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if there are conflicting modmap definitions</dd>
+</dl>
+
+@todo detailed explanation and examples
+
+
+### XKB-883 – Conflicting key action {#XKB-883}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if there are conflicting actions while merging keys</dd>
+</dl>
+
+### XKB-893 – Conflicting key type {#XKB-893}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if there are conflicting key types while merging groups</dd>
+</dl>
+
+### XKB-935 – Conflicting key fields {#XKB-935}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if there are conflicting fields while merging keys</dd>
+</dl>
+
+### XKB-965 – Unresolved keymap symbol {#XKB-965}
+
+<dl>
+  <dt>Since</dt><dd>1.0.0</dd>
+  <dt>Type</dt><dd>Warning</dd>
+  <dt>Summary</dt><dd>Warn if using a symbol not defined in the keymap</dd>
+</dl>
+
+[XKB-034]: @ref XKB-034
+[XKB-060]: @ref XKB-060
+[XKB-107]: @ref XKB-107
+[XKB-183]: @ref XKB-183
+[XKB-237]: @ref XKB-237
+[XKB-286]: @ref XKB-286
+[XKB-305]: @ref XKB-305
+[XKB-312]: @ref XKB-312
+[XKB-461]: @ref XKB-461
+[XKB-516]: @ref XKB-516
+[XKB-578]: @ref XKB-578
+[XKB-645]: @ref XKB-645
+[XKB-700]: @ref XKB-700
+[XKB-769]: @ref XKB-769
+[XKB-770]: @ref XKB-770
+[XKB-800]: @ref XKB-800
+[XKB-883]: @ref XKB-883
+[XKB-893]: @ref XKB-893
+[XKB-935]: @ref XKB-935
+[XKB-965]: @ref XKB-965

doc/message-registry.md.jinja

@@ -0,0 +1,74 @@
+# Error index { {#--#} #error-index}
+
+{# NOTE: Prevent Doxygen issue by writing the comment after the first header. #}
+<!--
+NOTE: This file has been generated automatically by “{{script}}”.
+      Do not edit manually!
+-->
+
+This page lists the warnings and errors generated by xkbcommon.
+There are currently {{ entries|length }} entries.
+
+@todo The documentation of the log messages is a work in progress.
+
+## Index
+
+| Code      | Identifier                   | Description | Type |
+| --------- | ---------------------------- | ----------- | ---- |
+{% for entry in entries %}
+| [{{entry.message_code}}] | `{{entry.id}}` | {{entry.description|prepend_todo}} | {{entry.type|capitalize}} |
+{% endfor %}
+
+## Details
+
+{% for entry in entries %}
+### {{entry.message_code}} – {{entry.message_name}} { {#--#}#{{entry.message_code}}}
+
+<dl>
+{% if entry.removed %}
+  <dt>Added in</dt><dd>{{entry.added}}</dd>
+  <dt>Removed in</dt><dd>{{entry.removed}}</dd>
+{% else %}
+  <dt>Since</dt><dd>{{entry.added}}</dd>
+{% endif %}
+  <dt>Type</dt><dd>{{entry.type|capitalize}}</dd>
+  <dt>Summary</dt><dd>{{entry.description|prepend_todo}}</dd>
+</dl>
+
+{% if entry.details %}
+{{entry.details}}
+
+{% endif %}
+{% if entry.examples %}
+#### Examples
+
+{% for example in entry.examples %}
+<details>
+  <summary>{{example.name}}</summary>
+
+{{example.description}}
+{% if example.before %}
+**Fix:**
+  <div class="example-container">
+    <div class="example">
+      <div class="example-inner">
+        <div class="example-title">Before</div>
+{{example.before-}}
+      </div>
+    </div>
+    <div class="example">
+      <div class="example-inner">
+        <div class="example-title">After</div>
+{{example.after-}}
+      </div>
+    </div>
+  </div>
+{% endif %}
+</details>
+
+{% endfor %}
+{% endif %}
+{% endfor %}
+{% for entry in entries %}
+[{{entry.message_code}}]: @ref {{entry.message_code}}
+{% endfor %}

doc/message-registry.yaml

@@ -0,0 +1,176 @@
+# Guidelines:
+# • A message code must always have the same meaning forever.
+# • Codes may be retired or introduced in new releases. In order to avoid
+#   clashes, retired codes must not be deleted.
+# • Codes should not themselves reflect classification, e.g. a range for parse
+#   errors and a range for each keymap component.
+# • Codes should not be assigned sequentially because it is misleading.
+# • Codes must be in the range 1..999. This range may be extended once every
+#   code has be assigned.
+#
+# See the following guidelines for futher details on good practices:
+# https://github.com/haskellfoundation/error-message-index/blob/main/tool-developers.md#code-assignment-recommendations
+
+# NOTE: Field “added: ALWAYS” means that the precise version is unknown and
+# anterior to the introduction of the message registry. It will be replaced by
+# the default version 1.0.0 in the generated documentation. While this is deemed
+# good enough to avoid spelunking commit history, a more precise version would
+# be welcome.
+
+# TODO: fix missing detailed description, examples, resolution
+
+- id: "malformed-number-literal"
+  code: 34
+  added: ALWAYS
+  type: error
+  description: "Warn on malformed number literals"
+  details: |
+    xkbcommon can parse the following number literal formats:
+
+    - *decimal integer:* 1, 123, etc.
+    - *decimal floating-point number:* 1.23, etc.
+    - *hexadecimal integer:* prefixed with “0x”: 0x123, 0xff, 0xAB, etc.
+- id: "unsupported-modifier-mask"
+  code: 60
+  added: ALWAYS
+  type: error
+  description: "Warn on unsupported modifier mask"
+- id: "unrecognized-keysym"
+  code: 107
+  added: ALWAYS
+  type: warning
+  description: "Warn on unrecognized keysyms"
+  details: |
+    xkbcommon replaces keysyms it does not recognize by the keysym `NoSymbol`.
+
+    You may find the list of supported keysyms in
+    `include/xkbcommon/xkbcommon-keysyms.h`.
+  examples:
+    - name: Unrecognized keysym “`coma`”
+      description: |
+        **Error message:**
+
+        ```
+        xkbcommon: WARNING: [XKB-107] de:31:20: unrecognized keysym "coma"
+        ```
+
+        xkbcommon does not recognize the keysym “`coma`”. It is most probably
+        a typo for “<code>com<em>m</em>a</code>”.
+        See: `XKB_KEY_comma` in `include/xkbcommon/xkbcommon-keysyms.h`.
+      before: |
+        ```c
+        key <AB08> {[ coma, semicolon, periodcentered, multiply ]};
+        ```
+      after: |
+        ```c
+        key <AB08> {[ comma, semicolon, periodcentered, multiply ]};
+        ```
+- id: "cannot-infer-key-type"
+  code: 183
+  added: ALWAYS
+  type: warning
+  description: "Warn if no key type can be inferred"
+- id: "unsupported-group-index"
+  code: 237
+  added: ALWAYS
+  type: error
+  description: "Warn when a group index is not supported"
+  details: |
+    xkbcommon supports group index in the range (1..{{XKB_MAX_GROUPS}}).
+- id: "undefined-key-type"
+  code: 286
+  added: ALWAYS
+  type: warning
+  description: "Warn if using an undefined key type"
+- id: "non-base-group-name"
+  code: 305
+  added: ALWAYS
+  type: warning
+  description: "Warn if a group name was defined for group other than the first one"
+- id: "unsupported-shift-level"
+  code: 312
+  added: ALWAYS
+  type: error
+  description: "Warn when a shift level is not supported"
+  details: |
+    Shift levels are _one_-indexed. xkbcommon supports two formats of shift levels:
+    as numbers and as identifiers `LevelN`, where `N` is in the range (1..8).
+- id: "conflicting-key-symbol"
+  code: 461
+  added: ALWAYS
+  type: warning
+  description: "Warn if there are conflicting keysyms while merging keys"
+- id: "extra-symbols-ignored"
+  code: 516
+  added: ALWAYS
+  type: warning
+  description: "TODO: add description"
+- id: "wrong-field-type"
+  code: 578
+  added: ALWAYS
+  type: error
+  description: "Warn when a field has not the expected type"
+- id: "unknown-char-escape-sequence"
+  code: 645
+  added: ALWAYS
+  type: warning
+  description: "Warn on unknown escape sequence in string literal"
+  details: |
+    xkbcommon support the following escape sequences in string literals:
+
+    | Escape sequence | Corresponding character             |
+    | --------------- | ----------------------------------- |
+    | `\b`            | `U+0008` Backspace                  |
+    | `\t`            | `U+0009` Character tabulation       |
+    | `\n`            | `U+000A` Line feed                  |
+    | `\v`            | `U+000B` Vertical tabulation        |
+    | `\f`            | `U+000C` Form feed                  |
+    | `\r`            | `U+000D` Carriage return            |
+    | `\e`            | `U+001B` Escape                     |
+    | `\\`            | `U+005C` Backslash                  |
+    | `\NNN`          | _Octal_ escape, from `\0` to `\777` |
+- id: "multiple-groups-at-once"
+  code: 700
+  added: ALWAYS
+  type: warning
+  description: "Warn if a key defines multiple groups at once"
+- id: "invalid-syntax"
+  code: 769
+  added: ALWAYS
+  type: error
+  description: "The syntax is invalid and the file cannot be parsed"
+- id: "undefined-keycode"
+  code: 770
+  added: ALWAYS
+  type: warning
+  description: "TODO: add description"
+- id: "conflicting-modmap"
+  code: 800
+  added: ALWAYS
+  type: warning
+  description: "Warn if there are conflicting modmap definitions"
+  details: |
+    @todo detailed explanation and examples
+- id: "conflicting-key-action"
+  code: 883
+  added: ALWAYS
+  type: warning
+  description: "Warn if there are conflicting actions while merging keys"
+- id: "conflicting-key-type"
+  code: 893
+  added: ALWAYS
+  type: warning
+  description: "Warn if there are conflicting key types while merging groups"
+- id: "conflicting-key-fields"
+  code: 935
+  added: ALWAYS
+  type: warning
+  description: "Warn if there are conflicting fields while merging keys"
+- id: "unresolved-keymap-symbol"
+  code: 965
+  added: ALWAYS
+  type: warning
+  description: "Warn if using a symbol not defined in the keymap"
+
+# TODO: deprecated keysym
+# TODO: unicode keysym when named and recommended keysym exists

meson.build

@@ -221,6 +221,7 @@ libxkbcommon_sources = [
     'src/keymap.c',
     'src/keymap.h',
     'src/keymap-priv.c',
+    'src/messages-codes.h',
     'src/scanner-utils.h',
     'src/state.c',
     'src/text.c',
@@ -816,6 +817,7 @@ You can disable the documentation with -Denable-docs=false.''')
         'doc/user-configuration.md',
         'doc/rules-format.md',
         'doc/keymap-format-text-v1.md',
+        'doc/message-registry.md',
         'include/xkbcommon/xkbcommon.h',
         'include/xkbcommon/xkbcommon-compose.h',
         'include/xkbcommon/xkbcommon-keysyms.h',

scripts/update-message-registry.py

@@ -0,0 +1,275 @@
+#!/usr/bin/env python3
+
+from __future__ import annotations
+
+import argparse
+from dataclasses import astuple, dataclass
+from pathlib import Path
+import re
+from typing import Callable, Generic, Sequence, TypeVar
+
+import jinja2
+import yaml
+
+
+@dataclass(order=True)
+class Version:
+    """A semantic version number: MAJOR.MINOR.PATCH."""
+
+    UNKNOWN_VERSION = "ALWAYS"
+    DEFAULT_VERSION = "1.0.0"
+
+    major: int
+    minor: int
+    patch: int = 0
+
+    def __str__(self):
+        return ".".join(map(str, astuple(self)))
+
+    @classmethod
+    def parse(cls, raw_version: str) -> Version:
+        if raw_version == cls.UNKNOWN_VERSION:
+            raw_version = cls.DEFAULT_VERSION
+        version = raw_version.split(".")
+        assert 2 <= len(version) <= 3 and all(
+            n.isdecimal() for n in version
+        ), raw_version
+        return Version(*map(int, version))
+
+
+@dataclass
+class Example:
+    """An example in a message entry."""
+
+    name: str
+    description: str
+    before: str | None
+    after: str | None
+
+    @classmethod
+    def parse(cls, entry) -> Example:
+        name = entry.get("name")
+        assert name, entry
+
+        description = entry.get("description")
+        assert description
+
+        before = entry.get("before")
+        after = entry.get("after")
+        # Either none or both of them
+        assert not (bool(before) ^ bool(after))
+
+        return Example(name=name, description=description, before=before, after=after)
+
+
+@dataclass
+class Entry:
+    """An xkbcommon message entry in the message registry"""
+
+    VALID_TYPES = ("warning", "error")
+
+    code: int
+    """A unique strictly positive integer identifier"""
+    id: str
+    """A unique short human-readable string identifier"""
+    type: str
+    """Log level of the message"""
+    description: str
+    """A short description of the meaning of the message"""
+    details: str
+    """A long description of the meaning of the message"""
+    added: Version
+    """Version of xkbcommon the message has been added"""
+    removed: Version | None
+    """Version of xkbcommon the message has been removed"""
+    examples: tuple[Example, ...]
+    """
+    Optional examples of situations in which the message occurs.
+    If the message is an error or a warning, also provide hints on how to fix it.
+    """
+
+    @classmethod
+    def parse(cls, entry) -> Entry:
+        code = entry.get("code")
+        assert code is not None and isinstance(code, int) and code > 0, entry
+
+        id = entry.get("id")
+        assert id is not None, entry
+
+        type_ = entry.get("type")
+        assert type_ in cls.VALID_TYPES, entry
+
+        description = entry.get("description")
+        assert description is not None, entry
+
+        details = entry.get("details", "")
+
+        raw_added = entry.get("added", "")
+        assert raw_added, entry
+
+        added = Version.parse(raw_added)
+        assert added, entry
+
+        if removed := entry.get("removed"):
+            removed = Version.parse(removed)
+            assert added < removed, entry
+
+        if examples := entry.get("examples", ()):
+            examples = tuple(map(Example.parse, examples))
+
+        return Entry(
+            code=code,
+            id=id,
+            type=type_,
+            description=description,
+            added=added,
+            removed=removed,
+            details=details,
+            examples=examples,
+        )
+
+    @property
+    def message_code(self) -> str:
+        """Format the message code for display"""
+        return f"XKB-{self.code:0>3}"
+
+    @property
+    def message_code_constant(self: Entry) -> str:
+        """Returns the C enumeration member denoting the message code"""
+        id = self.id.replace("-", "_").upper()
+        return f"XKB_{self.type.upper()}_{id}"
+
+    @property
+    def message_name(self: Entry):
+        """Format the message string identifier for display"""
+        return self.id.replace("-", " ").capitalize()
+
+
+def prepend_todo(text: str) -> str:
+    if text.startswith("TODO"):
+        return f"""<span class="todo">{text[:5]}</span>{text[5:]}"""
+    else:
+        return text
+
+
+def load_message_registry(
+    env: jinja2.Environment, constants: dict[str, int], path: Path
+) -> Sequence[Entry]:
+    # Load the message registry YAML file as a Jinja2 template
+    registry_template = env.get_template(str(path))
+
+    # Load message registry
+    message_registry = sorted(
+        map(Entry.parse, yaml.safe_load(registry_template.render(constants))),
+        key=lambda e: e.code,
+    )
+
+    # Check message codes and identifiers are unique
+    codes: set[int] = set()
+    identifiers: set[str] = set()
+    for n, entry in enumerate(message_registry):
+        if entry.code in codes:
+            raise ValueError("Duplicated code in entry #{n}: {entry.code}")
+        if entry.id in identifiers:
+            raise ValueError("Duplicated identifier in entry #{n}: {entry.id}")
+        codes.add(entry.code)
+        identifiers.add(entry.id)
+
+    return message_registry
+
+
+def generate(
+    registry: Sequence[Entry],
+    env: jinja2.Environment,
+    root: Path,
+    file: Path,
+    skip_removed: bool = False,
+):
+    """Generate a file from its Jinja2 template and the message registry"""
+    template_path = file.with_suffix(f"{file.suffix}.jinja")
+    template = env.get_template(str(template_path))
+    path = root / file
+    script = Path(__file__).name
+    with path.open("wt", encoding="utf-8") as fd:
+        entries = (
+            tuple(filter(lambda e: e.removed is None, registry))
+            if skip_removed
+            else registry
+        )
+        fd.writelines(template.generate(entries=entries, script=script))
+
+
+T = TypeVar("T")
+
+
+@dataclass
+class Constant(Generic[T]):
+    name: str
+    pattern: re.Pattern
+    conversion: Callable[[str], T]
+
+
+def read_constants(path: Path, patterns: Sequence[Constant[T]]) -> dict[str, T]:
+    constants: dict[str, T] = {}
+    patternsʹ = list(patterns)
+    with path.open("rt", encoding="utf-8") as fd:
+        for line in fd:
+            for k, constant in enumerate(patternsʹ):
+                if m := constant.pattern.match(line):
+                    constants[constant.name] = constant.conversion(m.group(1))
+                    del patternsʹ[k]
+                    continue  # Expect only one match per line
+            if not patternsʹ:
+                # No more pattern to match
+                break
+    for constant in patternsʹ:
+        print(f"ERROR: could not find constant: {constant.name}.")
+    if patternsʹ:
+        raise ValueError("Some constants were not found.")
+    return constants
+
+
+# Root of the project
+ROOT = Path(__file__).parent.parent
+
+# Parse commands
+parser = argparse.ArgumentParser(description="Generate files from the message registry")
+parser.add_argument(
+    "--root",
+    type=Path,
+    default=ROOT,
+    help="Path to the root of the project (default: %(default)s)",
+)
+
+args = parser.parse_args()
+
+# Read some constants from libxkbcommon that we need
+constants = read_constants(
+    Path(__file__).parent.parent / "src" / "keymap.h",
+    (Constant("XKB_MAX_GROUPS", re.compile("^#define\s+XKB_MAX_GROUPS\s+(\d+)"), int),),
+)
+
+# Configure Jinja
+template_loader = jinja2.FileSystemLoader(args.root, encoding="utf-8")
+jinja_env = jinja2.Environment(
+    loader=template_loader,
+    keep_trailing_newline=True,
+    trim_blocks=True,
+    lstrip_blocks=True,
+)
+jinja_env.filters["prepend_todo"] = prepend_todo
+
+# Load message registry
+message_registry = load_message_registry(
+    jinja_env, constants, Path("doc/message-registry.yaml")
+)
+
+# Generate the files
+generate(
+    message_registry,
+    jinja_env,
+    args.root,
+    Path("src/messages-codes.h"),
+    skip_removed=True,
+)
+generate(message_registry, jinja_env, args.root, Path("doc/message-registry.md"))

src/context.h

@@ -27,6 +27,7 @@
 #define CONTEXT_H
 
 #include "atom.h"
+#include "messages-codes.h"
 
 struct xkb_context {
     int refcnt;
@@ -114,16 +115,31 @@ xkb_context_sanitize_rule_names(struct xkb_context *ctx,
  * format is supplied without arguments. Not supplying it would still
  * result in an error, though.
  */
+#define xkb_log_with_code(ctx, level, verbosity, msg_id, fmt, ...) \
+    xkb_log(ctx, level, verbosity, "[XKB-%03d] " fmt, \
+            msg_id, ##__VA_ARGS__)
+#define log_dbg_with_code(ctx, id, ...) \
+    xkb_log_with_code((ctx), XKB_LOG_LEVEL_DEBUG, 0, (id), __VA_ARGS__)
 #define log_dbg(ctx, ...) \
     xkb_log((ctx), XKB_LOG_LEVEL_DEBUG, 0, __VA_ARGS__)
+#define log_info_with_code(ctx, id, ...) \
+    xkb_log_with_code((ctx), XKB_LOG_LEVEL_INFO, 0, (id), __VA_ARGS__)
 #define log_info(ctx, ...) \
     xkb_log((ctx), XKB_LOG_LEVEL_INFO, 0, __VA_ARGS__)
+#define log_warn_with_code(ctx, id, ...) \
+    xkb_log_with_code((ctx), XKB_LOG_LEVEL_WARNING, 0, (id), __VA_ARGS__)
 #define log_warn(ctx, ...) \
     xkb_log((ctx), XKB_LOG_LEVEL_WARNING, 0, __VA_ARGS__)
+#define log_err_with_code(ctx, id, ...) \
+    xkb_log_with_code((ctx), XKB_LOG_LEVEL_ERROR, 0, (id), __VA_ARGS__)
 #define log_err(ctx, ...) \
     xkb_log((ctx), XKB_LOG_LEVEL_ERROR, 0, __VA_ARGS__)
+#define log_wsgo_with_code(ctx, id, ...) \
+    xkb_log_with_code((ctx), XKB_LOG_LEVEL_CRITICAL, 0, (id), __VA_ARGS__)
 #define log_wsgo(ctx, ...) \
     xkb_log((ctx), XKB_LOG_LEVEL_CRITICAL, 0, __VA_ARGS__)
+#define log_vrb_with_code(ctx, vrb, id, ...) \
+    xkb_log_with_code((ctx), XKB_LOG_LEVEL_WARNING, (vrb), (id), __VA_ARGS__)
 #define log_vrb(ctx, vrb, ...) \
     xkb_log((ctx), XKB_LOG_LEVEL_WARNING, (vrb), __VA_ARGS__)
 

src/messages-codes.h

@@ -0,0 +1,62 @@
+// NOTE: This file has been generated automatically by “update-message-registry.py”.
+//       Do not edit manually!
+
+#ifndef MESSAGES_H
+#define MESSAGES_H
+
+#include <stdint.h>
+
+/**
+ * @name Codes of the log messages
+ *
+ * @added 1.6.0
+ *
+ */
+enum xkb_message_code {
+    _XKB_LOG_MESSAGE_MIN_CODE = 34,
+    /** Warn on malformed number literals */
+    XKB_ERROR_MALFORMED_NUMBER_LITERAL = 34,
+    /** Warn on unsupported modifier mask */
+    XKB_ERROR_UNSUPPORTED_MODIFIER_MASK = 60,
+    /** Warn on unrecognized keysyms */
+    XKB_WARNING_UNRECOGNIZED_KEYSYM = 107,
+    /** Warn if no key type can be inferred */
+    XKB_WARNING_CANNOT_INFER_KEY_TYPE = 183,
+    /** Warn when a group index is not supported */
+    XKB_ERROR_UNSUPPORTED_GROUP_INDEX = 237,
+    /** Warn if using an undefined key type */
+    XKB_WARNING_UNDEFINED_KEY_TYPE = 286,
+    /** Warn if a group name was defined for group other than the first one */
+    XKB_WARNING_NON_BASE_GROUP_NAME = 305,
+    /** Warn when a shift level is not supported */
+    XKB_ERROR_UNSUPPORTED_SHIFT_LEVEL = 312,
+    /** Warn if there are conflicting keysyms while merging keys */
+    XKB_WARNING_CONFLICTING_KEY_SYMBOL = 461,
+    /** TODO: add description */
+    XKB_WARNING_EXTRA_SYMBOLS_IGNORED = 516,
+    /** Warn when a field has not the expected type */
+    XKB_ERROR_WRONG_FIELD_TYPE = 578,
+    /** Warn on unknown escape sequence in string literal */
+    XKB_WARNING_UNKNOWN_CHAR_ESCAPE_SEQUENCE = 645,
+    /** Warn if a key defines multiple groups at once */
+    XKB_WARNING_MULTIPLE_GROUPS_AT_ONCE = 700,
+    /** The syntax is invalid and the file cannot be parsed */
+    XKB_ERROR_INVALID_SYNTAX = 769,
+    /** TODO: add description */
+    XKB_WARNING_UNDEFINED_KEYCODE = 770,
+    /** Warn if there are conflicting modmap definitions */
+    XKB_WARNING_CONFLICTING_MODMAP = 800,
+    /** Warn if there are conflicting actions while merging keys */
+    XKB_WARNING_CONFLICTING_KEY_ACTION = 883,
+    /** Warn if there are conflicting key types while merging groups */
+    XKB_WARNING_CONFLICTING_KEY_TYPE = 893,
+    /** Warn if there are conflicting fields while merging keys */
+    XKB_WARNING_CONFLICTING_KEY_FIELDS = 935,
+    /** Warn if using a symbol not defined in the keymap */
+    XKB_WARNING_UNRESOLVED_KEYMAP_SYMBOL = 965,
+    _XKB_LOG_MESSAGE_MAX_CODE = 965
+};
+
+typedef uint32_t xkb_message_code_t;
+
+#endif

src/messages-codes.h.jinja

@@ -0,0 +1,26 @@
+// NOTE: This file has been generated automatically by “{{script}}”.
+//       Do not edit manually!
+
+#ifndef MESSAGES_H
+#define MESSAGES_H
+
+#include <stdint.h>
+
+/**
+ * @name Codes of the log messages
+ *
+ * @added 1.6.0
+ *
+ */
+enum xkb_message_code {
+    _XKB_LOG_MESSAGE_MIN_CODE = {{ entries[0].code }},
+    {% for entry in entries %}
+    /** {{ entry.description }} */
+    {{ entry.message_code_constant }} = {{ entry.code }},
+    {% endfor %}
+    _XKB_LOG_MESSAGE_MAX_CODE = {{ entries[-1].code }}
+};
+
+typedef uint32_t xkb_message_code_t;
+
+#endif

src/scanner-utils.h

@@ -57,15 +57,28 @@ struct scanner {
     void *priv;
 };
 
+#define scanner_log_with_code(scanner, level, log_msg_id, fmt, ...) \
+    xkb_log_with_code((scanner)->ctx, (level), 0, log_msg_id, \
+                    "%s:%zu:%zu: " fmt "\n", \
+                    (scanner)->file_name, \
+                    (scanner)->token_line, \
+                    (scanner)->token_column, ##__VA_ARGS__)
+
 #define scanner_log(scanner, level, fmt, ...) \
     xkb_log((scanner)->ctx, (level), 0, \
             "%s:%zu:%zu: " fmt "\n", \
             (scanner)->file_name, \
             (scanner)->token_line, (scanner)->token_column, ##__VA_ARGS__)
 
+#define scanner_err_with_code(scanner, id, fmt, ...) \
+    scanner_log_with_code(scanner, XKB_LOG_LEVEL_ERROR, id, fmt, ##__VA_ARGS__)
+
 #define scanner_err(scanner, fmt, ...) \
     scanner_log(scanner, XKB_LOG_LEVEL_ERROR, fmt, ##__VA_ARGS__)
 
+#define scanner_warn_with_code(scanner, id, fmt, ...) \
+    scanner_log_with_code(scanner, XKB_LOG_LEVEL_WARNING, id, fmt, ##__VA_ARGS__)
+
 #define scanner_warn(scanner, fmt, ...) \
     scanner_log(scanner, XKB_LOG_LEVEL_WARNING, fmt, ##__VA_ARGS__)
 

src/xkbcomp/action.c

@@ -190,10 +190,11 @@ fieldText(enum action_field field)
 /***====================================================================***/
 
 static inline bool
-ReportMismatch(struct xkb_context *ctx, enum xkb_action_type action,
+ReportMismatch(struct xkb_context *ctx, xkb_message_code_t code,
-               enum action_field field, const char *type)
+               enum xkb_action_type action, enum action_field field,
+               const char *type)
 {
-    log_err(ctx,
+    log_err_with_code(ctx, code,
             "Value of %s field must be of type %s; "
             "Action %s definition ignored\n",
             fieldText(field), type, ActionTypeText(action));
@@ -243,7 +244,8 @@ CheckBooleanFlag(struct xkb_context *ctx, enum xkb_action_type action,
         return ReportActionNotArray(ctx, action, field);
 
     if (!ExprResolveBoolean(ctx, value, &set))
-        return ReportMismatch(ctx, action, field, "boolean");
+        return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE,
+                              action, field, "boolean");
 
     if (set)
         *flags_inout |= flag;
@@ -274,7 +276,7 @@ CheckModifierField(struct xkb_context *ctx, const struct xkb_mod_set *mods,
     }
 
     if (!ExprResolveModMask(ctx, value, MOD_BOTH, mods, mods_rtrn))
-        return ReportMismatch(ctx, action,
+        return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE, action,
                               ACTION_FIELD_MODIFIERS, "modifier mask");
 
     *flags_inout &= ~ACTION_MODS_LOOKUP_MODMAP;
@@ -300,7 +302,8 @@ CheckAffectField(struct xkb_context *ctx, enum xkb_action_type action,
         return ReportActionNotArray(ctx, action, ACTION_FIELD_AFFECT);
 
     if (!ExprResolveEnum(ctx, value, &flags, lockWhich))
-        return ReportMismatch(ctx, action, ACTION_FIELD_AFFECT,
+        return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE,
+                              action, ACTION_FIELD_AFFECT,
                               "lock, unlock, both, neither");
 
     *flags_inout &= ~(ACTION_LOCK_NO_LOCK | ACTION_LOCK_NO_UNLOCK);
@@ -359,8 +362,8 @@ CheckGroupField(struct xkb_context *ctx, enum xkb_action_type action,
     }
 
     if (!ExprResolveGroup(ctx, spec, &idx))
-        return ReportMismatch(ctx, action, ACTION_FIELD_GROUP,
+        return ReportMismatch(ctx, XKB_ERROR_UNSUPPORTED_GROUP_INDEX, action,
-                              "integer (range 1..8)");
+                              ACTION_FIELD_GROUP, "integer (range 1..8)");
 
     /* +n, -n are relative, n is absolute. */
     if (value->expr.op == EXPR_NEGATE || value->expr.op == EXPR_UNARY_PLUS) {
@@ -416,7 +419,8 @@ HandleMovePtr(struct xkb_context *ctx, const struct xkb_mod_set *mods,
             return ReportActionNotArray(ctx, action->type, field);
 
         if (!ExprResolveInteger(ctx, value, &val))
-            return ReportMismatch(ctx, action->type, field, "integer");
+            return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE, action->type,
+                                  field, "integer");
 
         if (val < INT16_MIN || val > INT16_MAX) {
             log_err(ctx,
@@ -462,8 +466,8 @@ HandlePtrBtn(struct xkb_context *ctx, const struct xkb_mod_set *mods,
             return ReportActionNotArray(ctx, action->type, field);
 
         if (!ExprResolveButton(ctx, value, &btn))
-            return ReportMismatch(ctx, action->type, field,
+            return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE, action->type,
-                                  "integer (range 1..5)");
+                                  field, "integer (range 1..5)");
 
         if (btn < 0 || btn > 5) {
             log_err(ctx,
@@ -487,7 +491,8 @@ HandlePtrBtn(struct xkb_context *ctx, const struct xkb_mod_set *mods,
             return ReportActionNotArray(ctx, action->type, field);
 
         if (!ExprResolveInteger(ctx, value, &val))
-            return ReportMismatch(ctx, action->type, field, "integer");
+            return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE, action->type,
+                                  field, "integer");
 
         if (val < 0 || val > 255) {
             log_err(ctx,
@@ -524,8 +529,8 @@ HandleSetPtrDflt(struct xkb_context *ctx, const struct xkb_mod_set *mods,
             return ReportActionNotArray(ctx, action->type, field);
 
         if (!ExprResolveEnum(ctx, value, &val, ptrDflts))
-            return ReportMismatch(ctx, action->type, field,
+            return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE, action->type,
-                                  "pointer component");
+                                  field, "pointer component");
         return true;
     }
     else if (field == ACTION_FIELD_BUTTON || field == ACTION_FIELD_VALUE) {
@@ -546,8 +551,8 @@ HandleSetPtrDflt(struct xkb_context *ctx, const struct xkb_mod_set *mods,
         }
 
         if (!ExprResolveButton(ctx, button, &btn))
-            return ReportMismatch(ctx, action->type, field,
+            return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE, action->type,
-                                  "integer (range 1..5)");
+                                  field, "integer (range 1..5)");
 
         if (btn < 0 || btn > 5) {
             log_err(ctx,
@@ -594,8 +599,8 @@ HandleSwitchScreen(struct xkb_context *ctx, const struct xkb_mod_set *mods,
         }
 
         if (!ExprResolveInteger(ctx, scrn, &val))
-            return ReportMismatch(ctx, action->type, field,
+            return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE, action->type,
-                                  "integer (0..255)");
+                                  field, "integer (0..255)");
 
         if (val < 0 || val > 255) {
             log_err(ctx,
@@ -630,8 +635,8 @@ HandleSetLockControls(struct xkb_context *ctx, const struct xkb_mod_set *mods,
             return ReportActionNotArray(ctx, action->type, field);
 
         if (!ExprResolveMask(ctx, value, &mask, ctrlMaskNames))
-            return ReportMismatch(ctx, action->type, field,
+            return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE, action->type,
-                                  "controls mask");
+                                  field, "controls mask");
 
         act->ctrls = mask;
         return true;
@@ -658,7 +663,8 @@ HandlePrivate(struct xkb_context *ctx, const struct xkb_mod_set *mods,
             return ReportActionNotArray(ctx, action->type, field);
 
         if (!ExprResolveInteger(ctx, value, &type))
-            return ReportMismatch(ctx, ACTION_TYPE_PRIVATE, field, "integer");
+            return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE,
+                                  ACTION_TYPE_PRIVATE, field, "integer");
 
         if (type < 0 || type > 255) {
             log_err(ctx,
@@ -696,7 +702,8 @@ HandlePrivate(struct xkb_context *ctx, const struct xkb_mod_set *mods,
             size_t len;
 
             if (!ExprResolveString(ctx, value, &val))
-                return ReportMismatch(ctx, action->type, field, "string");
+                return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE,
+                                      action->type, field, "string");
 
             str = xkb_atom_text(ctx, val);
             len = strlen(str);
@@ -731,7 +738,8 @@ HandlePrivate(struct xkb_context *ctx, const struct xkb_mod_set *mods,
             }
 
             if (!ExprResolveInteger(ctx, value, &datum))
-                return ReportMismatch(ctx, act->type, field, "integer");
+                return ReportMismatch(ctx, XKB_ERROR_WRONG_FIELD_TYPE, act->type,
+                                      field, "integer");
 
             if (datum < 0 || datum > 255) {
                 log_err(ctx,

src/xkbcomp/compat.c

@@ -124,7 +124,8 @@ static inline bool
 ReportSIBadType(CompatInfo *info, SymInterpInfo *si, const char *field,
                 const char *wanted)
 {
-    return ReportBadType(info->ctx, "symbol interpretation", field,
+    return ReportBadType(info->ctx, XKB_ERROR_WRONG_FIELD_TYPE,
+                         "symbol interpretation", field,
                          siText(si, info), wanted);
 }
 
@@ -132,7 +133,8 @@ static inline bool
 ReportLedBadType(CompatInfo *info, LedInfo *ledi, const char *field,
                  const char *wanted)
 {
-    return ReportBadType(info->ctx, "indicator map", field,
+    return ReportBadType(info->ctx, XKB_ERROR_WRONG_FIELD_TYPE,
+                         "indicator map", field,
                          xkb_atom_text(info->ctx, ledi->led.name),
                          wanted);
 }

src/xkbcomp/expr.c

@@ -407,7 +407,8 @@ ExprResolveGroup(struct xkb_context *ctx, const ExprDef *expr,
         return false;
 
     if (result <= 0 || result > XKB_MAX_GROUPS) {
-        log_err(ctx, "Group index %u is out of range (1..%d)\n",
+        log_err_with_code(ctx, XKB_ERROR_UNSUPPORTED_GROUP_INDEX,
+                          "Group index %u is out of range (1..%d)\n",
                           result, XKB_MAX_GROUPS);
         return false;
     }
@@ -429,7 +430,8 @@ ExprResolveLevel(struct xkb_context *ctx, const ExprDef *expr,
         return false;
 
     if (result < 1) {
-        log_err(ctx, "Shift level %d is out of range\n", result);
+        log_err_with_code(ctx, XKB_ERROR_UNSUPPORTED_SHIFT_LEVEL,
+                          "Shift level %d is out of range\n", result);
         return false;
     }
 
@@ -658,7 +660,8 @@ ExprResolveKeySym(struct xkb_context *ctx, const ExprDef *expr,
         return false;
 
     if (val < XKB_KEYSYM_MIN) {
-        log_warn(ctx, "unrecognized keysym \"-0x%x\" (%d)\n",
+        log_warn_with_code(ctx, XKB_WARNING_UNRECOGNIZED_KEYSYM,
+                           "unrecognized keysym \"-0x%x\" (%d)\n",
                            (unsigned int) -val, val);
         return false;
     }
@@ -674,7 +677,9 @@ ExprResolveKeySym(struct xkb_context *ctx, const ExprDef *expr,
         return true;
     }
 
-    log_warn(ctx, "unrecognized keysym \"0x%x\" (%d)\n", val, val);
+    log_warn_with_code(ctx, XKB_WARNING_UNRECOGNIZED_KEYSYM,
+                       "unrecognized keysym \"0x%x\" (%d)\n",
+                       (unsigned int) val, val);
     return false;
 
 }

src/xkbcomp/keycodes.c

@@ -472,7 +472,8 @@ HandleLedNameDef(KeyNamesInfo *info, LedNameDef *def,
         char buf[20];
         snprintf(buf, sizeof(buf), "%u", def->ndx);
         info->errorCount++;
-        return ReportBadType(info->ctx, "indicator", "name", buf, "string");
+        return ReportBadType(info->ctx, XKB_ERROR_WRONG_FIELD_TYPE,
+                             "indicator", "name", buf, "string");
     }
 
     ledi.merge = merge;

src/xkbcomp/parser.y

@@ -46,16 +46,16 @@ struct parser_param {
     bool more_maps;
 };
 
-#define parser_err(param, fmt, ...) \
+#define parser_err(param, error_id, fmt, ...) \
-    scanner_err((param)->scanner, fmt, ##__VA_ARGS__)
+    scanner_err_with_code((param)->scanner, error_id, fmt, ##__VA_ARGS__)
 
-#define parser_warn(param, fmt, ...) \
+#define parser_warn(param, warning_id, fmt, ...) \
-    scanner_warn((param)->scanner, fmt, ##__VA_ARGS__)
+    scanner_warn_with_code((param)->scanner, warning_id, fmt, ##__VA_ARGS__)
 
 static void
 _xkbcommon_error(struct parser_param *param, const char *msg)
 {
-    parser_err(param, "%s", msg);
+    parser_err(param, XKB_ERROR_INVALID_SYNTAX, "%s", msg);
 }
 
 static bool
@@ -728,7 +728,12 @@ KeySyms         :       OBRACE KeySymList CBRACE
 KeySym          :       IDENT
                         {
                             if (!resolve_keysym($1, &$$)) {
-                                parser_warn(param, "unrecognized keysym \"%s\"", $1);
+                                parser_warn(
+                                    param,
+                                    XKB_WARNING_UNRECOGNIZED_KEYSYM,
+                                    "unrecognized keysym \"%s\"",
+                                    $1
+                                );
                                 $$ = XKB_KEY_NoSymbol;
                             }
                             free($1);
@@ -737,7 +742,12 @@ KeySym          :       IDENT
                 |       Integer
                         {
                             if ($1 < XKB_KEYSYM_MIN) {
-                                parser_warn(param, "unrecognized keysym \"%"PRId64"\"", $1);
+                                parser_warn(
+                                    param,
+                                    XKB_WARNING_UNRECOGNIZED_KEYSYM,
+                                    "unrecognized keysym \"%"PRId64"\"",
+                                    $1
+                                );
                                 $$ = XKB_KEY_NoSymbol;
                             }
                             /* Special case for digits 0..9 */
@@ -748,7 +758,11 @@ KeySym          :       IDENT
                                 if ($1 <= XKB_KEYSYM_MAX) {
                                     $$ = (xkb_keysym_t) $1;
                                 } else {
-                                    parser_warn(param, "unrecognized keysym \"0x%"PRIx64"\"", $1);
+                                    parser_warn(
+                                        param, XKB_WARNING_UNRECOGNIZED_KEYSYM,
+                                        "unrecognized keysym \"0x%"PRIx64"\" "
+                                        "(%"PRId64")", $1, $1
+                                    );
                                     $$ = XKB_KEY_NoSymbol;
                                 }
                             }

src/xkbcomp/scanner.c

@@ -100,7 +100,10 @@ skip_more_whitespace_and_comments:
                 else if (scanner_chr(s, 'e'))  scanner_buf_append(s, '\033');
                 else if (scanner_oct(s, &o))   scanner_buf_append(s, (char) o);
                 else {
-                    scanner_warn(s, "unknown escape sequence in string literal");
+                    // TODO: display actual sequence! See: scanner_peek(s).
+                    //       require escaping any potential control character
+                    scanner_warn_with_code(s, XKB_WARNING_UNKNOWN_CHAR_ESCAPE_SEQUENCE,
+                                           "unknown escape sequence in string literal");
                     /* Ignore. */
                 }
             } else {
@@ -171,7 +174,8 @@ skip_more_whitespace_and_comments:
     /* Number literal (hexadecimal / decimal / float). */
     if (number(s, &yylval->num, &tok)) {
         if (tok == ERROR_TOK) {
-            scanner_err(s, "malformed number literal");
+            scanner_err_with_code(s, XKB_ERROR_MALFORMED_NUMBER_LITERAL,
+                                  "malformed number literal");
             return ERROR_TOK;
         }
         return tok;

src/xkbcomp/symbols.c

@@ -61,6 +61,10 @@
 #include "include.h"
 #include "keysym.h"
 
+
+// TODO: convert log_err to log_err_with_code
+// TODO: convert log_vrb to log_vrb_with_code
+
 enum key_repeat {
     KEY_REPEAT_UNDEFINED = 0,
     KEY_REPEAT_YES = 1,
@@ -240,13 +244,15 @@ MergeGroups(SymbolsInfo *info, GroupInfo *into, GroupInfo *from, bool clobber,
             xkb_atom_t use = (clobber ? from->type : into->type);
             xkb_atom_t ignore = (clobber ? into->type : from->type);
 
-            if (report)
+            if (report) {
-                log_warn(info->ctx,
+                log_warn_with_code(info->ctx,
+                         XKB_WARNING_CONFLICTING_KEY_TYPE,
                          "Multiple definitions for group %d type of key %s; "
                          "Using %s, ignoring %s\n",
                          group + 1, KeyNameText(info->ctx, key_name),
                          xkb_atom_text(info->ctx, use),
                          xkb_atom_text(info->ctx, ignore));
+            }
 
             into->type = use;
         }
@@ -284,13 +290,15 @@ MergeGroups(SymbolsInfo *info, GroupInfo *into, GroupInfo *from, bool clobber,
             use = (clobber ? &fromLevel->action : &intoLevel->action);
             ignore = (clobber ? &intoLevel->action : &fromLevel->action);
 
-            if (report)
+            if (report) {
-                log_warn(info->ctx,
+                log_warn_with_code(info->ctx,
+                         XKB_WARNING_CONFLICTING_KEY_ACTION,
                          "Multiple actions for level %d/group %u on key %s; "
                          "Using %s, ignoring %s\n",
                          i + 1, group + 1, KeyNameText(info->ctx, key_name),
                          ActionTypeText(use->type),
                          ActionTypeText(ignore->type));
+            }
 
             intoLevel->action = *use;
         }
@@ -307,13 +315,15 @@ MergeGroups(SymbolsInfo *info, GroupInfo *into, GroupInfo *from, bool clobber,
             fromLevel->num_syms = 0;
         }
         else if (!XkbLevelsSameSyms(fromLevel, intoLevel)) {
-            if (report)
+            if (report) {
-                log_warn(info->ctx,
+                log_warn_with_code(info->ctx,
+                         XKB_WARNING_CONFLICTING_KEY_SYMBOL,
                          "Multiple symbols for level %d/group %u on key %s; "
                          "Using %s, ignoring %s\n",
                          i + 1, group + 1, KeyNameText(info->ctx, key_name),
                          (clobber ? "from" : "to"),
                          (clobber ? "to" : "from"));
+            }
 
             if (clobber) {
                 ClearLevelInfo(intoLevel);
@@ -406,12 +416,14 @@ MergeKeys(SymbolsInfo *info, KeyInfo *into, KeyInfo *from, bool same_file)
         into->defined |= KEY_FIELD_GROUPINFO;
     }
 
-    if (collide)
+    if (collide) {
-        log_warn(info->ctx,
+        log_warn_with_code(info->ctx,
+                 XKB_WARNING_CONFLICTING_KEY_FIELDS,
                  "Symbol map for key %s redefined; "
                  "Using %s definition for conflicting fields\n",
                  KeyNameText(info->ctx, into->name),
                  (clobber ? "first" : "last"));
+    }
 
     ClearKeyInfo(from);
     InitKeyInfo(info->ctx, from);
@@ -464,21 +476,23 @@ AddModMapEntry(SymbolsInfo *info, ModMapEntry *new)
         use = (clobber ? new->modifier : old->modifier);
         ignore = (clobber ? old->modifier : new->modifier);
 
-        if (new->haveSymbol)
+        if (new->haveSymbol) {
-            log_warn(info->ctx,
+            log_warn_with_code(info->ctx,
+                     XKB_WARNING_CONFLICTING_MODMAP,
                      "Symbol \"%s\" added to modifier map for multiple modifiers; "
                      "Using %s, ignoring %s\n",
                      KeysymText(info->ctx, new->u.keySym),
                      ModIndexText(info->ctx, &info->mods, use),
                      ModIndexText(info->ctx, &info->mods, ignore));
-        else
+        } else {
-            log_warn(info->ctx,
+            log_warn_with_code(info->ctx,
+                     XKB_WARNING_CONFLICTING_MODMAP,
                      "Key \"%s\" added to modifier map for multiple modifiers; "
                      "Using %s, ignoring %s\n",
                      KeyNameText(info->ctx, new->u.keyName),
                      ModIndexText(info->ctx, &info->mods, use),
                      ModIndexText(info->ctx, &info->mods, ignore));
-
+        }
         old->modifier = use;
         return true;
     }
@@ -639,7 +653,7 @@ GetGroupIndex(SymbolsInfo *info, KeyInfo *keyi, ExprDef *arrayNdx,
     }
 
     if (!ExprResolveGroup(info->ctx, arrayNdx, ndx_rtrn)) {
-        log_err(info->ctx,
+        log_err_with_code(info->ctx, XKB_ERROR_UNSUPPORTED_GROUP_INDEX,
                 "Illegal group index for %s of key %s\n"
                 "Definition with non-integer array index ignored\n",
                 name, KeyInfoText(info, keyi));
@@ -812,7 +826,7 @@ SetSymbolsField(SymbolsInfo *info, KeyInfo *keyi, const char *field,
             keyi->defined |= KEY_FIELD_DEFAULT_TYPE;
         }
         else if (!ExprResolveGroup(info->ctx, arrayNdx, &ndx)) {
-            log_err(info->ctx,
+            log_err_with_code(info->ctx, XKB_ERROR_UNSUPPORTED_GROUP_INDEX,
                     "Illegal group index for type of key %s; "
                     "Definition with non-integer array index ignored\n",
                     KeyInfoText(info, keyi));
@@ -924,7 +938,7 @@ SetSymbolsField(SymbolsInfo *info, KeyInfo *keyi, const char *field,
         xkb_layout_index_t grp;
 
         if (!ExprResolveGroup(info->ctx, value, &grp)) {
-            log_err(info->ctx,
+            log_err_with_code(info->ctx, XKB_ERROR_UNSUPPORTED_GROUP_INDEX,
                     "Illegal group index for redirect of key %s; "
                     "Definition with non-integer group ignored\n",
                     KeyInfoText(info, keyi));
@@ -960,7 +974,7 @@ SetGroupName(SymbolsInfo *info, ExprDef *arrayNdx, ExprDef *value)
     }
 
     if (!ExprResolveGroup(info->ctx, arrayNdx, &group)) {
-        log_err(info->ctx,
+        log_err_with_code(info->ctx, XKB_ERROR_UNSUPPORTED_GROUP_INDEX,
                 "Illegal index in group name definition; "
                 "Definition with non-integer array index ignored\n");
         return false;
@@ -980,7 +994,8 @@ SetGroupName(SymbolsInfo *info, ExprDef *arrayNdx, ExprDef *value)
         group_to_use = info->explicit_group;
     }
     else {
-        log_warn(info->ctx,
+        log_warn_with_code(info->ctx,
+                 XKB_WARNING_NON_BASE_GROUP_NAME,
                  "An explicit group was specified for the '%s' map, "
                  "but it provides a name for a group other than Group1 (%d); "
                  "Ignoring group name '%s'\n",
@@ -1098,12 +1113,14 @@ SetExplicitGroup(SymbolsInfo *info, KeyInfo *keyi)
         }
     }
 
-    if (warn)
+    if (warn) {
-        log_warn(info->ctx,
+        log_warn_with_code(info->ctx,
+                 XKB_WARNING_MULTIPLE_GROUPS_AT_ONCE,
                  "For the map %s an explicit group specified, "
                  "but key %s has more than one group defined; "
                  "All groups except first one will be ignored\n",
                  info->name, KeyInfoText(info, keyi));
+    }
 
     darray_resize0(keyi->groups, info->explicit_group + 1);
     if (info->explicit_group > 0) {
@@ -1371,7 +1388,8 @@ FindTypeForGroup(struct xkb_keymap *keymap, KeyInfo *keyi,
     }
 
     if (type_name == XKB_ATOM_NONE) {
-        log_warn(keymap->ctx,
+        log_warn_with_code(keymap->ctx,
+                 XKB_WARNING_CANNOT_INFER_KEY_TYPE,
                  "Couldn't find an automatic type for key '%s' group %d with %lu levels; "
                  "Using the default type\n",
                  KeyNameText(keymap->ctx, keyi->name), group + 1,
@@ -1384,7 +1402,8 @@ FindTypeForGroup(struct xkb_keymap *keymap, KeyInfo *keyi,
             break;
 
     if (i >= keymap->num_types) {
-        log_warn(keymap->ctx,
+        log_warn_with_code(keymap->ctx,
+                 XKB_WARNING_UNDEFINED_KEY_TYPE,
                  "The type \"%s\" for key '%s' group %d was not previously defined; "
                  "Using the default type\n",
                  xkb_atom_text(keymap->ctx, type_name),
@@ -1417,7 +1436,8 @@ CopySymbolsDefToKeymap(struct xkb_keymap *keymap, SymbolsInfo *info,
      */
     key = XkbKeyByName(keymap, keyi->name, false);
     if (!key) {
-        log_vrb(info->ctx, 5,
+        log_vrb_with_code(info->ctx, 5,
+                XKB_WARNING_UNDEFINED_KEYCODE,
                 "Key %s not found in keycodes; Symbols ignored\n",
                 KeyInfoText(info, keyi));
         return false;
@@ -1460,7 +1480,8 @@ CopySymbolsDefToKeymap(struct xkb_keymap *keymap, SymbolsInfo *info,
         if (type->num_levels < darray_size(groupi->levels)) {
             struct xkb_level *leveli;
 
-            log_vrb(info->ctx, 1,
+            log_vrb_with_code(info->ctx, 1,
+                    XKB_WARNING_EXTRA_SYMBOLS_IGNORED,
                     "Type \"%s\" has %d levels, but %s has %d levels; "
                     "Ignoring extra symbols\n",
                     xkb_atom_text(keymap->ctx, type->name), type->num_levels,
@@ -1512,7 +1533,8 @@ CopyModMapDefToKeymap(struct xkb_keymap *keymap, SymbolsInfo *info,
     if (!entry->haveSymbol) {
         key = XkbKeyByName(keymap, entry->u.keyName, true);
         if (!key) {
-            log_vrb(info->ctx, 5,
+            log_vrb_with_code(info->ctx, 5,
+                    XKB_WARNING_UNDEFINED_KEYCODE,
                     "Key %s not found in keycodes; "
                     "Modifier map entry for %s not updated\n",
                     KeyNameText(info->ctx, entry->u.keyName),
@@ -1523,7 +1545,8 @@ CopyModMapDefToKeymap(struct xkb_keymap *keymap, SymbolsInfo *info,
     else {
         key = FindKeyForSymbol(keymap, entry->u.keySym);
         if (!key) {
-            log_vrb(info->ctx, 5,
+            log_vrb_with_code(info->ctx, 5,
+                    XKB_WARNING_UNRESOLVED_KEYMAP_SYMBOL,
                     "Key \"%s\" not found in symbol map; "
                     "Modifier map entry for %s not updated\n",
                     KeysymText(info->ctx, entry->u.keySym),

src/xkbcomp/types.c

@@ -89,10 +89,10 @@ ReportTypeShouldBeArray(KeyTypesInfo *info, KeyTypeInfo *type,
 }
 
 static inline bool
-ReportTypeBadType(KeyTypesInfo *info, KeyTypeInfo *type,
+ReportTypeBadType(KeyTypesInfo *info, xkb_message_code_t code,
-                  const char *field, const char *wanted)
+                  KeyTypeInfo *type, const char *field, const char *wanted)
 {
-    return ReportBadType(info->ctx, "key type", field,
+    return ReportBadType(info->ctx, code, "key type", field,
                          TypeTxt(info, type), wanted);
 }
 
@@ -340,7 +340,8 @@ SetMapEntry(KeyTypesInfo *info, KeyTypeInfo *type, ExprDef *arrayNdx,
 
     if (!ExprResolveModMask(info->ctx, arrayNdx, MOD_BOTH, &info->mods,
                             &entry.mods.mods))
-        return ReportTypeBadType(info, type, "map entry", "modifier mask");
+        return ReportTypeBadType(info, XKB_ERROR_UNSUPPORTED_MODIFIER_MASK,
+                                 type, "map entry", "modifier mask");
 
     if (entry.mods.mods & (~type->mods)) {
         log_vrb(info->ctx, 1,
@@ -354,7 +355,7 @@ SetMapEntry(KeyTypesInfo *info, KeyTypeInfo *type, ExprDef *arrayNdx,
     }
 
     if (!ExprResolveLevel(info->ctx, value, &entry.level)) {
-        log_err(info->ctx,
+        log_err_with_code(info->ctx, XKB_ERROR_UNSUPPORTED_SHIFT_LEVEL,
                           "Level specifications in a key type must be integer; "
                           "Ignoring malformed level specification\n");
         return false;
@@ -429,8 +430,8 @@ SetPreserve(KeyTypesInfo *info, KeyTypeInfo *type, ExprDef *arrayNdx,
         return ReportTypeShouldBeArray(info, type, "preserve entry");
 
     if (!ExprResolveModMask(info->ctx, arrayNdx, MOD_BOTH, &info->mods, &mods))
-        return ReportTypeBadType(info, type, "preserve entry",
+        return ReportTypeBadType(info, XKB_ERROR_UNSUPPORTED_MODIFIER_MASK,
-                                 "modifier mask");
+                                 type, "preserve entry", "modifier mask");
 
     if (mods & ~type->mods) {
         const char *before, *after;
@@ -526,7 +527,8 @@ SetLevelName(KeyTypesInfo *info, KeyTypeInfo *type, ExprDef *arrayNdx,
         return ReportTypeShouldBeArray(info, type, "level name");
 
     if (!ExprResolveLevel(info->ctx, arrayNdx, &level))
-        return ReportTypeBadType(info, type, "level name", "integer");
+        return ReportTypeBadType(info, XKB_ERROR_UNSUPPORTED_SHIFT_LEVEL,
+                                 type, "level name", "integer");
 
     if (!ExprResolveString(info->ctx, value, &level_name)) {
         log_err(info->ctx,

src/xkbcomp/xkbcomp-priv.h

@@ -101,10 +101,10 @@ ReportShouldBeArray(struct xkb_context *ctx, const char *type,
 }
 
 static inline bool
-ReportBadType(struct xkb_context *ctx, const char *type, const char *field,
+ReportBadType(struct xkb_context *ctx, xkb_message_code_t code, const char *type,
-              const char *name, const char *wanted)
+              const char *field, const char *name, const char *wanted)
 {
-    log_err(ctx, "The %s %s field must be a %s; "
+    log_err_with_code(ctx, code, "The %s %s field must be a %s; "
             "Ignoring illegal assignment in %s\n",
             type, field, wanted, name);
     return false;