gnatdoc

name	gnatdoc
description	This skill should be used when the user wants to "generate API documentation", "generate Ada documentation", "run gnatdoc", "document an Ada package", "annotate Ada code with GNATdoc tags", "use @param/@return/@field/@enum/@exception/@exclude tags", "produce HTML/ODF/RST/XML docs for Ada code", or is otherwise working with GNATdoc to extract documentation from Ada sources.
license	Apache-2.0
metadata	{"version":"0.1.0"}

GNATdoc Documentation Generation Skill

gnatdoc is AdaCore's documentation generator for Ada. It parses an Ada project, extracts documentation comments from the source code (using a cross-reference engine for accuracy), and emits an annotated HTML site (default), an OpenDocument Format document, a set of reStructuredText files, or an XML dump.

gnatdoc is not a free-form generator — it requires a GNAT project file (.gpr) and reads only the comments at well-defined locations (preceding or following declarations, depending on the configured style).

Locating GNATdoc

Unless the user has already told you how to invoke gnatdoc, determine the right invocation in this order:

1. Check for an alire.toml in the project root. Its presence means the project is an Alire crate. Invoke gnatdoc via alr exec -- gnatdoc -P <project.gpr> ... so Alire injects the correct environment (GPR_PROJECT_PATH, PATH, etc.) before the tool runs.

2. Check if gnatdoc is already on PATH. Run which gnatdoc. If found, use it — but if runs fail with project-file resolution errors, the environment may be incomplete (see step 3). gnatdoc ships as part of the GNAT Studio package, so it is typically installed alongside GNAT Studio's other binaries.

3. Ask the user. GNAT Pro and GNAT Studio installations (commonly under /usr/gnat, /opt/gnat, or a vendor-specific path) typically require environment setup beyond a binary on PATH. Don't guess — ask the user how they want to configure the environment.

Quick Start

gnatdoc always requires a project file. The minimal invocation is:

gnatdoc -P <project.gpr>

This generates HTML documentation under <obj>/gnatdoc/html/ (the default output is <obj>/gnatdoc/<backend-name>/, where <obj> is the object directory of the root project). Open index.html in that directory to view the output.

A more complete invocation that names the backend explicitly, enables undocumented-entity warnings, and tees the output for later inspection:

gnatdoc --backend=html --warnings -P <project.gpr> 2>&1 | tee gnatdoc-run.txt

Common arguments:

Flag	Effect
-P, --project FILE	Project file. Required.
--backend=<html|odf|rst|rstpt|xml>	Output format. Default html. See references/backends.md.
--html-oop-style	(HTML backend only) Group subprograms by tagged type, generating a separate page for each tagged type. Replaces the older --backend=html:oop syntax.
--generate=<public|private|body>	Which entities to document. public (default) = public part of specs; private = public + private spec; body = specs + library-level body entities. See references/command-reference.md.
--style=<leading|trailing|gnat>	Where documentation comments sit relative to declarations. Default gnat; trailing and gnat are equivalent. See references/styles.md.
-O, --output-dir DIR	Override the output directory. Overrides Documentation'Output_Dir in the project file.
-X NAME=VALUE	Set a scenario variable on the project. Repeatable.
--warnings	Emit warnings for every undocumented entity — subprograms, parameters, return values, components, discriminants, enumeration literals, generic formals, raised exceptions. Informational only; it never changes the generated output. See Verifying a run for how to act on the list.
-v, --verbose	Verbose output.
--version	Print the GNATdoc version and exit. Useful for diagnosing behavior differences across builds.
--print-gpr-registry	Print the supported Documentation package GPR attributes and exit.

Verifying a run

A zero exit code from gnatdoc does not mean the documentation is complete or correct. After every run, check at least these:

1. The output directory exists. Default is <obj>/gnatdoc/<backend>/ (e.g. <obj>/gnatdoc/html/). If you passed -O or set Documentation'Output_Dir, look there instead.
2. The entry-point file is present. For HTML that is index.html inside the output directory; for ODF, the .fodt file; for RST, the set of .rst files; for XML, the produced .xml file.
3. The captured log (gnatdoc-run.txt if you teed) has no error lines and the expected warning lines. Search for warning: and error: — --warnings reports undocumented entities here. Treat that list as a coverage report, not a to-do list: address warnings for entities you added or modified, but leave pre-existing warnings alone unless the user has asked for a wider documentation campaign — report them to the user instead.
4. Open the entry-point file. Spot-check that the units you expect are present and the doc comments rendered as intended. A blank line or wrong indentation silently disassociates a comment from its entity: with --warnings the entity is then reported as "not documented", but nothing ever points at the stray comment itself.

Mandatory pre-work

Before running gnatdoc on a new project, do these in order:

1. Make sure the project builds with the standard toolchain. Use the same invocation environment as the one you'll use for gnatdoc itself — alr exec -- gprbuild -P <project.gpr> for Alire crates, plain gprbuild -P <project.gpr> otherwise. gnatdoc parses sources as GNAT sees them; an unbuildable project will not be processable, and an environment mismatch between gprbuild and gnatdoc will mask the real issue.

2. Determine the documentation style. --style=leading, --style=trailing, and --style=gnat change where gnatdoc looks for the comment block attached to each declaration; mixing styles within a project leads to silently dropped documentation. If the user or the existing build scripts specify a style, use it. Otherwise survey the sources to match the existing convention, and ask the user only if the survey is inconclusive. See references/styles.md § Determining a project's existing style. Record the choice in the build script that invokes gnatdoc — no project-file attribute exists for the style.

3. Agree on the documentation scope. Ask the user which entities to document: --generate=public (public spec only — the default), --generate=private (public + private spec), or --generate=body (also library-level body entities). If they express no preference, use the default public. See references/command-reference.md § generate.

Core principles

• A .gpr project file is mandatory. gnatdoc cannot operate on loose source files.

• Default output is transient. Without Documentation'Output_Dir (or -O), output lands under the object directory, where it is typically gitignored and deleted by gprclean. For documentation you want to commit or publish, set Output_Dir to a path outside obj/, or pass -O <path>. See references/project-setup.md.

• Comments must be adjacent to the declaration. A blank line between the doc block and the declaration breaks the association. Keep doc comments tight against the entity they describe.

• gnatdoc skips externally-built projects. Recursive processing walks the full dependency graph except externally-built projects (typically prebuilt third-party libraries). To exclude additional projects, use Documentation'Excluded_Project_Files. See references/project-setup.md.

Reference files

Topic	File	When to read
CLI switches and their semantics	command-reference.md	Looking up any gnatdoc flag or its effect
Documentation tags (@param, @return, @field, @enum, @exception, @exclude, …) and where comment blocks attach	annotations.md	Writing or fixing documentation comments in Ada sources
leading vs. trailing vs. gnat styles	styles.md	Determining an existing project's style, choosing one for a new project, or migrating
Documentation package attributes in .gpr (Documentation_Pattern, Excluded_Project_Files, Output_Dir, Resources_Dir, Image_Dirs)	project-setup.md	Configuring gnatdoc declaratively in the project file
Backends (HTML, ODF, RST, XML), OOP layout switches (--html-oop-style, --rst-oop-style), resource directory layouts	backends.md	Picking an output format or customizing rendering