doxygen-guard 1.2.6

Pre-commit hook that validates doxygen comments for presence, version staleness, and custom tag syntax

doxygen-guard

Pre-commit hook that validates doxygen comments, generates PlantUML sequence diagrams, and produces change-impact reports. Architecture-agnostic — works with event-driven, sequential, async IPC, and any other pattern.

Quick Start

1. Add the hook to .pre-commit-config.yaml

repos:
  - repo: https://github.com/tvanfossen/doxygen-guard
    rev: main
    hooks:
      - id: doxygen-guard
        types_or: [c, c++, java, python]

2. Create .doxygen-guard.yaml in your repo root

output_dir: docs/generated/

validate:
  exclude:
    - "^tests/"
    - "^\\.venv/"

trace:
  format: plantuml
  participant_field: "Subsystem"
  static_participants:
    - name: User
      type: actor
  external:
    - Cloud:
        receives_prefix: ["MQTT:"]
        boundary_functions: ["CloudMgr_Publish"]
        label_template: "MQTT: {arg0}"
        entry_chain:
          - { from: User, to: Mobile, label: "{req_name}" }
          - { from: Mobile, to: Cloud, label: "{req_name}" }
    - MCU:
        receives_prefix: ["DURABLE:"]
        boundary_functions: ["DurableEventCb"]
  options:
    show_returns: false
    label_mode: brief

impact:
  requirements:
    file: docs/requirements.csv
    id_column: "Req ID"
    name_column: "Name"
    format: csv

3. Add doxygen to your functions

/** @participant Sensor Driver */

/**
 * @brief Read temperature from sensor hardware.
 * @version 1.0
 * @req REQ-0010
 * @return Raw ADC value
 */
int Sensor_ReadTemperature(void) {
    int raw = hw_read_adc(TEMP_CHANNEL);
    event_post(EVENT_SENSOR_DATA_READY, raw);
    return raw;
}

Run pre-commit run --all-files — diagrams appear in docs/generated/sequences/.

What It Does

Validation (pre-commit gate)

Every function in staged files is checked for:

• Presence — must have @brief, @version, and @return (non-void functions)
• Version staleness — if function body changed (git diff), @version must be updated
• Tag syntax — tag values validated against configured patterns
• Requirement coverage — functions must have @req or an exemption tag

Sequence Diagrams (auto-generated)

Behavioral sequence diagrams are generated from annotations. Most tags are inferred from AST:

Tag	Purpose	Manual?
@req	Requirement mapping	Yes — per function
@participant	Participant identity	Yes — once per file
@note	Diagram notes (doxygen built-in)	Yes — per function
@after	Precondition cross-reference	Yes — per function
@loop	Wrap handler in loop block	Yes — per function
@group	Wrap handler in group block	Yes — per function
@return	Return value documentation	Yes — per function
@send_source	Infrastructure root (e.g., on Event_post)	Yes — once
@receive_source	Registration root (e.g., on Event_register)	Yes — once
@sends	Events emitted	Inferred from AST
@receives	Events handled	Inferred from AST
@calls	Cross-module boundary calls	Inferred from AST

The tool scans function bodies via tree-sitter to detect event_post() calls, Event_register() patterns, and cross-participant function calls automatically.

Diagram Features

• Entry chains — upstream participant arrows (User→Mobile→Cloud) prepended from config
• Label templates — protocol labels from boundary function args (MQTT: {arg0})
• Hub backtracking — REQs routed through dispatch hubs get entry chains automatically
• Control flow blocks (if/else, loops) from AST
• Loop/group wrappers — @loop and @group tags for repeated/grouped handlers
• Boundary argument extraction — function args rendered on arrows via tree-sitter
• Incremental generation — SHA-256 manifest skips unchanged diagrams

Exemption Tags

Tag	Validation	Trace
@internal	Exempt from @req	Invisible — never in any diagram
@utility	Exempt from @req	Visible — appears as call target
@callback	Exempt from @req	Normal visibility

Change-Impact Reports

Cross-references git diff with parsed functions to show which requirements are affected by staged changes. Reports in markdown and JSON at <output_dir>/impact/.

Configuration Reference

validate section

Key	Type	Default	Description
languages	dict	C, C++, Java, Python	Per-language function patterns and comment styles
presence.require_doxygen	bool	true	Require doxygen on every function
presence.require_return	bool	true	Require @return on non-void functions
presence.skip_forward_declarations	bool	true	Skip C/C++ forward declarations
version.require_present	bool	true	Require @version tag
version.require_increment_on_change	bool	true	Require version bump when body changes
exclude	list	[]	Regex patterns for files to skip (applies to both validation and trace)
tags.req.cross_reference	bool	true	Validate @req IDs exist in requirements file
version_gate.current_version	string	—	auto:git, auto:cmake, or explicit version
version_gate.version_field	string	—	Column in requirements file for version gating

trace section

Key	Type	Default	Description
format	string	plantuml	Diagram output format
participant_field	string	—	Requirements file column for participant resolution
static_participants	list	[]	Actors/entities always shown (e.g., {name: User, type: actor})
external	list	[]	External participants (see below)
external_fallback	string	External	Fallback name for unresolved sources (warns and omits in behavioral mode)

External participants

Route events to named external actors by prefix. Boundary functions produce protocol-labeled arrows via label_template. Entry chains prepend upstream participant arrows.

trace:
  external:
    - Cloud:
        receives_prefix: ["MQTT:"]
        boundary_functions: ["CloudMgr_Publish"]
        label_template: "MQTT: {arg0}"
        entry_chain:
          - { from: User, to: Mobile, label: "{req_name}" }
          - { from: Mobile, to: Cloud, label: "{req_name}" }
    - MCU:
        receives_prefix: ["DURABLE:"]
        boundary_functions: ["DurableEventCb"]
    - Hardware:
        receives_prefix: ["EVENT_HW_"]

Sub-key	Purpose
receives_prefix	Route @receives events matching these prefixes to this participant
boundary_functions	Function names that cross this system boundary (for @calls edges)
label_template	Format boundary call labels — {arg0}, {arg1} substituted from call args
entry_chain	Upstream participant arrows prepended before entry edge

trace.options

Key	Type	Default	Description
autonumber	bool	true	Number sequence arrows
box_label	string	System	Internal participant box label
box_color	string	#LightBlue	Internal participant box color
min_edges	int	1	Minimum behavioral edges to generate a diagram
show_returns	bool	false	Show return arrows and activation bars on @calls edges
show_recovery_notes	bool	true	Show callee names in empty catch blocks
max_condition_length	int	80	Truncation limit for alt/loop conditions
infer_sends	bool	true	Infer @sends from event post function calls
infer_calls	bool	true	Infer @calls from cross-module calls
event_send_functions	list	[]	Event post function names for generated code (escape hatch)
event_receive_functions	list	[]	Registration function names for generated code (escape hatch)
legend	bool	false	Render arrow style legend
label_mode	string	brief	Label style: full (event+function), brief (event name only)

impact section

Key	Type	Default	Description
requirements.file	string	—	Path to requirements file
requirements.format	string	csv	Format: csv, json, or yaml
requirements.id_column	string	Req ID	Requirement ID column/field
requirements.name_column	string	Requirement Name	Requirement name column/field

File-Level Doxygen

Each source file should have a file-level doxygen block. Use @participant to set the participant name for all functions in the file:

/**
 * @file
 * @brief Sensor hardware abstraction layer.
 * @version 1.0
 * @participant Sensor Driver
 */

The requirements-file participant_field takes precedence over @participant for participant resolution. @participant is the fallback when no requirements mapping exists. Enable validate.presence.require_file_doxygen: true to enforce file-level blocks.

For Python:

## @file
## @brief Configuration loading and validation.
## @version 1.0
## @participant Config

Infrastructure Roots

Mark event bus functions once to enable automatic inference:

/**
 * @brief Post an event to all registered handlers.
 * @version 1.0
 * @req REQ-0050
 * @send_source
 */
void Event_post(uint64_t event, void *data) { ... }

/**
 * @brief Register a handler for events matching a bitmask.
 * @version 1.0
 * @req REQ-0050
 * @receive_source
 */
void Event_register(uint64_t mask, event_handler_fn handler) { ... }

With these in place, @sends and @receives are derived from the AST for all other functions — zero manual behavioral tags needed.

Generated Code

For code generators that rebuild files on every build (UDM, protobuf, HAL generators), annotations on generated files are destroyed. Use event_send_functions and event_receive_functions as config-level overrides:

trace:
  options:
    event_send_functions: ["dm_event_callback"]
    event_receive_functions: ["register_fsm_handler"]

These tell the tool to treat calls to these functions as send/registration points, equivalent to @send_source / @receive_source but without requiring tags on the generated source. Use this only for generated code you cannot annotate. For code you own, use @send_source / @receive_source tags instead.

Both default to empty lists — @send_source / @receive_source tags are the primary mechanism.

Config Validation

The config file is validated at load time against a built-in schema. Unknown keys are rejected with an error message:

doxygen-guard config error: Unknown key 'trace.optoins' — did you mean 'trace.options'?

trace.options values are type-checked after merge with defaults. Invalid types produce warnings:

WARNING: trace.options.min_edges must be int >= 0, got 'banana'

Adopting on an Existing Codebase

For repos with existing code that has no doxygen, adopt incrementally:

1. Start with validation only — add @brief and @version to functions as you touch them. Use version_gate to only enforce @req on functions added after a specific version:

validate:
  version_gate:
    current_version: "auto:git"
    version_field: "Min Version"

2. Add @participant to each file — one line per file sets the participant name for diagrams.

3. Add @return to non-void functions — required by default. Disable with presence.require_return: false during migration.

4. Mark infrastructure roots — if you have an event bus or message dispatcher, add @send_source/@receive_source once to enable automatic inference.

5. Exclude paths you're not ready to cover:

validate:
  exclude:
    - "^vendor/"
    - "^legacy/"

Supported Languages

Language	Extensions	Comment Style	Body Detection
C	.c, .h	/** ... */	Brace matching
C++	.cpp, .hpp, .cc, .cxx	/** ... */	Brace matching
Java	.java	/** ... */	Brace matching
Python	.py	## ...	Indentation

C++ template functions (template<typename T> void func(...)) are fully supported — doxygen comments are associated via tree-sitter AST sibling detection, handling template_declaration wrappers correctly.

CLI Usage

# Pre-commit mode (default — called by pre-commit)
doxygen-guard [--config path] [files...]

# Explicit subcommands
doxygen-guard validate --no-git src/*.c
doxygen-guard trace --all src/
doxygen-guard trace --req REQ-001 src/
doxygen-guard impact --staged src/*.c
doxygen-guard coverage src/

# Verbose mode
doxygen-guard -v trace --all src/

License

MIT — see LICENSE.