[PATCH v17 5/5] dts: add API doc generation

["Juraj Linkeš" <juraj.linkes@pantheon.tech>]

The tool used to generate DTS API docs is Sphinx, which is already in
use in DPDK. The same configuration is used to preserve style with one
DTS-specific configuration (so that the DPDK docs are unchanged) that
modifies how the sidebar displays the content. There's other Sphinx
configuration related to Python docstrings which doesn't affect DPDK doc
build. All new configuration is in a conditional block, applied only
when DTS API docs are built to not interfere with DPDK doc build.

Sphinx generates the documentation from Python docstrings. The docstring
format is the Google format [0] which requires the sphinx.ext.napoleon
extension. The other extension, sphinx.ext.intersphinx, enables linking
to objects in external documentations, such as the Python documentation.

There is one requirement for building DTS docs - the same Python version
as DTS or higher, because Sphinx's autodoc extension imports the code.

The dependencies needed to import the code don't have to be satisfied,
as the autodoc extension allows us to mock the imports. The missing
packages are taken from the DTS pyproject.toml file.

And finally, the DTS API docs can be accessed from the DPDK API doxygen
page.

[0] https://google.github.io/styleguide/pyguide.html#38-comments-and-docstrings

Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
---
 buildtools/call-sphinx-build.py           |  2 +
 buildtools/get-dts-runtime-deps.py        | 84 +++++++++++++++++++++++
 buildtools/meson.build                    |  1 +
 doc/api/doxy-api-index.md                 |  3 +
 doc/api/doxy-api.conf.in                  |  2 +
 doc/api/dts/custom.css                    |  1 +
 doc/api/dts/meson.build                   | 31 +++++++++
 doc/api/meson.build                       |  6 +-
 doc/guides/conf.py                        | 44 +++++++++++-
 doc/guides/contributing/documentation.rst |  2 +
 doc/guides/contributing/patches.rst       |  4 ++
 doc/guides/tools/dts.rst                  | 39 ++++++++++-
 doc/meson.build                           |  1 +
 13 files changed, 217 insertions(+), 3 deletions(-)
 create mode 100755 buildtools/get-dts-runtime-deps.py
 create mode 120000 doc/api/dts/custom.css
 create mode 100644 doc/api/dts/meson.build

diff --git a/buildtools/call-sphinx-build.py b/buildtools/call-sphinx-build.py
index 623e7363ee..154e9f907b 100755
--- a/buildtools/call-sphinx-build.py
+++ b/buildtools/call-sphinx-build.py
@@ -15,6 +15,8 @@
 
 # set the version in environment for sphinx to pick up
 os.environ['DPDK_VERSION'] = version
+if 'dts' in src:
+    os.environ['DTS_BUILD'] = "y"
 
 sphinx_cmd = [sphinx] + extra_args
 
diff --git a/buildtools/get-dts-runtime-deps.py b/buildtools/get-dts-runtime-deps.py
new file mode 100755
index 0000000000..68244480a3
--- /dev/null
+++ b/buildtools/get-dts-runtime-deps.py
@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2024 PANTHEON.tech s.r.o.
+#
+
+"""Utilities for DTS dependencies.
+
+The module can be used as an executable script,
+which verifies that the running Python version meets the version requirement of DTS.
+The script exits with the standard exit codes in this mode (0 is success, 1 is failure).
+
+The module also contains a function, get_missing_imports,
+which looks for runtime dependencies in the DTS pyproject.toml file
+and returns a list of module names used in an import statement (import packages) that are missing.
+This function is not used when the module is run as a script and is available to be imported.
+"""
+
+import configparser
+import importlib.metadata
+import importlib.util
+import os.path
+import platform
+
+from packaging.version import Version
+
+_VERSION_COMPARISON_CHARS = '^<>='
+_EXTRA_DEPS = {'invoke': '>=1.3', 'paramiko': '>=2.4'}
+_DPDK_ROOT = os.path.dirname(os.path.dirname(__file__))
+_DTS_DEP_FILE_PATH = os.path.join(_DPDK_ROOT, 'dts', 'pyproject.toml')
+
+
+def _get_dependencies(cfg_file_path):
+    cfg = configparser.ConfigParser()
+    with open(cfg_file_path) as f:
+        dts_deps_file_str = f.read()
+        dts_deps_file_str = dts_deps_file_str.replace("\n]", "]")
+        cfg.read_string(dts_deps_file_str)
+
+    deps_section = cfg['tool.poetry.dependencies']
+    return {dep: deps_section[dep].strip('"\'') for dep in deps_section}
+
+
+def get_missing_imports():
+    """Get missing DTS import packages from third party libraries.
+
+    Scan the DTS pyproject.toml file for dependencies and find those that are not installed.
+    The dependencies in pyproject.toml are listed by their distribution package names,
+    but the function finds the associated import packages - those used in import statements.
+
+    The function is not used when the module is run as a script. It should be imported.
+
+    Returns:
+        A list of missing import packages.
+    """
+    missing_imports = []
+    req_deps = _get_dependencies(_DTS_DEP_FILE_PATH)
+    req_deps.pop('python')
+
+    for req_dep, req_ver in (req_deps | _EXTRA_DEPS).items():
+        try:
+            req_ver = Version(req_ver.strip(_VERSION_COMPARISON_CHARS))
+            found_dep_ver = Version(importlib.metadata.version(req_dep))
+            if found_dep_ver < req_ver:
+                print(
+                    f'The version "{found_dep_ver}" of package "{req_dep}" '
+                    f'is lower than required "{req_ver}".'
+                )
+        except importlib.metadata.PackageNotFoundError:
+            print(f'Package "{req_dep}" not found.')
+            missing_imports.append(req_dep.lower().replace('-', '_'))
+
+    return missing_imports
+
+
+if __name__ == '__main__':
+    python_version = _get_dependencies(_DTS_DEP_FILE_PATH).pop('python')
+    if python_version:
+        sys_ver = Version(platform.python_version())
+        req_ver = Version(python_version.strip(_VERSION_COMPARISON_CHARS))
+        if sys_ver < req_ver:
+            print(
+                f'The available Python version "{sys_ver}" is lower than required "{req_ver}".'
+            )
+            exit(1)
diff --git a/buildtools/meson.build b/buildtools/meson.build
index 3adf34e1a8..6b938d767c 100644
--- a/buildtools/meson.build
+++ b/buildtools/meson.build
@@ -24,6 +24,7 @@ get_numa_count_cmd = py3 + files('get-numa-count.py')
 get_test_suites_cmd = py3 + files('get-test-suites.py')
 has_hugepages_cmd = py3 + files('has-hugepages.py')
 cmdline_gen_cmd = py3 + files('dpdk-cmdline-gen.py')
+get_dts_runtime_deps = py3 + files('get-dts-runtime-deps.py')
 
 # install any build tools that end-users might want also
 install_data([
diff --git a/doc/api/doxy-api-index.md b/doc/api/doxy-api-index.md
index f9f0300126..ab223bcdf7 100644
--- a/doc/api/doxy-api-index.md
+++ b/doc/api/doxy-api-index.md
@@ -245,3 +245,6 @@ The public API headers are grouped by topics:
   [experimental APIs](@ref rte_compat.h),
   [ABI versioning](@ref rte_function_versioning.h),
   [version](@ref rte_version.h)
+
+- **tests**:
+  [**DTS**](@dts_api_main_page)
diff --git a/doc/api/doxy-api.conf.in b/doc/api/doxy-api.conf.in
index a8823c046f..c94f02d411 100644
--- a/doc/api/doxy-api.conf.in
+++ b/doc/api/doxy-api.conf.in
@@ -124,6 +124,8 @@ SEARCHENGINE            = YES
 SORT_MEMBER_DOCS        = NO
 SOURCE_BROWSER          = YES
 
+ALIASES                 = "dts_api_main_page=@DTS_API_MAIN_PAGE@"
+
 EXAMPLE_PATH            = @TOPDIR@/examples
 EXAMPLE_PATTERNS        = *.c
 EXAMPLE_RECURSIVE       = YES
diff --git a/doc/api/dts/custom.css b/doc/api/dts/custom.css
new file mode 120000
index 0000000000..3c9480c4a0
--- /dev/null
+++ b/doc/api/dts/custom.css
@@ -0,0 +1 @@
+../../guides/custom.css
\ No newline at end of file
diff --git a/doc/api/dts/meson.build b/doc/api/dts/meson.build
new file mode 100644
index 0000000000..f338eb69bf
--- /dev/null
+++ b/doc/api/dts/meson.build
@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2023 PANTHEON.tech s.r.o.
+
+sphinx = find_program('sphinx-build', required: get_option('enable_docs'))
+if not sphinx.found()
+    subdir_done()
+endif
+
+python_ver_satisfied = run_command(get_dts_runtime_deps, check: false).returncode()
+if python_ver_satisfied != 0
+    subdir_done()
+endif
+
+cdata.set('DTS_API_MAIN_PAGE', join_paths('..', 'dts', 'html', 'index.html'))
+
+extra_sphinx_args = ['-E', '-c', join_paths(doc_source_dir, 'guides')]
+if get_option('werror')
+    extra_sphinx_args += '-W'
+endif
+
+htmldir = join_paths(get_option('datadir'), 'doc', 'dpdk', 'dts')
+dts_api_html = custom_target('dts_api_html',
+        output: 'html',
+        command: [sphinx_wrapper, sphinx, meson.project_version(),
+            meson.current_source_dir(), meson.current_build_dir(), extra_sphinx_args],
+        build_by_default: get_option('enable_docs'),
+        install: get_option('enable_docs'),
+        install_dir: htmldir)
+
+doc_targets += dts_api_html
+doc_target_names += 'DTS_API_HTML'
diff --git a/doc/api/meson.build b/doc/api/meson.build
index 5b50692df9..71b861e42b 100644
--- a/doc/api/meson.build
+++ b/doc/api/meson.build
@@ -1,6 +1,11 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright(c) 2018 Luca Boccassi <bluca@debian.org>
 
+# initialize common Doxygen configuration
+cdata = configuration_data()
+
+subdir('dts')
+
 doxygen = find_program('doxygen', required: get_option('enable_docs'))
 
 if not doxygen.found()
@@ -30,7 +35,6 @@ example = custom_target('examples.dox',
         build_by_default: get_option('enable_docs'))
 
 # set up common Doxygen configuration
-cdata = configuration_data()
 cdata.set('VERSION', meson.project_version())
 cdata.set('API_EXAMPLES', join_paths(dpdk_build_root, 'doc', 'api', 'examples.dox'))
 cdata.set('OUTPUT', join_paths(dpdk_build_root, 'doc', 'api'))
diff --git a/doc/guides/conf.py b/doc/guides/conf.py
index 0f7ff5282d..d7f3030838 100644
--- a/doc/guides/conf.py
+++ b/doc/guides/conf.py
@@ -10,7 +10,7 @@
 from os.path import basename
 from os.path import dirname
 from os.path import join as path_join
-from sys import argv, stderr
+from sys import argv, stderr, path
 
 import configparser
 
@@ -58,6 +58,48 @@
              ("tools/devbind", "dpdk-devbind",
               "check device status and bind/unbind them from drivers", "", 8)]
 
+# DTS API docs additional configuration
+if environ.get('DTS_BUILD'):
+    extensions = ['sphinx.ext.napoleon', 'sphinx.ext.autodoc', 'sphinx.ext.intersphinx']
+    # Napoleon enables the Google format of Python doscstrings.
+    napoleon_numpy_docstring = False
+    napoleon_attr_annotations = True
+    napoleon_preprocess_types = True
+
+    # Autodoc pulls documentation from code.
+    autodoc_default_options = {
+        'members': True,
+        'member-order': 'bysource',
+        'show-inheritance': True,
+    }
+    autodoc_class_signature = 'separated'
+    autodoc_typehints = 'both'
+    autodoc_typehints_format = 'short'
+    autodoc_typehints_description_target = 'documented'
+
+    # Intersphinx allows linking to external projects, such as Python docs.
+    intersphinx_mapping = {'python': ('https://docs.python.org/3', None)}
+
+    # DTS docstring options.
+    add_module_names = False
+    toc_object_entries = True
+    toc_object_entries_show_parents = 'hide'
+    # DTS Sidebar config.
+    html_theme_options = {
+        'collapse_navigation': False,
+        'navigation_depth': -1,  # unlimited depth
+    }
+
+    # Add path to DTS sources so that Sphinx can find them.
+    dpdk_root = dirname(dirname(dirname(__file__)))
+    path.append(path_join(dpdk_root, 'dts'))
+
+    # Get missing DTS dependencies. Add path to buildtools to find the get_missing_imports function.
+    path.append(path_join(dpdk_root, 'buildtools'))
+    import importlib
+    # Ignore missing imports from DTS dependencies.
+    autodoc_mock_imports = importlib.import_module('get-dts-runtime-deps').get_missing_imports()
+
 
 # ####### :numref: fallback ########
 # The following hook functions add some simple handling for the :numref:
diff --git a/doc/guides/contributing/documentation.rst b/doc/guides/contributing/documentation.rst
index 68454ae0d5..7b287ce631 100644
--- a/doc/guides/contributing/documentation.rst
+++ b/doc/guides/contributing/documentation.rst
@@ -133,6 +133,8 @@ added to by the developer.
 Building the Documentation
 --------------------------
 
+.. _doc_dependencies:
+
 Dependencies
 ~~~~~~~~~~~~
 
diff --git a/doc/guides/contributing/patches.rst b/doc/guides/contributing/patches.rst
index 04c66bebc4..6629928bee 100644
--- a/doc/guides/contributing/patches.rst
+++ b/doc/guides/contributing/patches.rst
@@ -499,6 +499,10 @@ The script usage is::
 For both of the above scripts, the -n option is used to specify a number of commits from HEAD,
 and the -r option allows the user specify a ``git log`` range.
 
+Additionally, when contributing to the DTS tool, patches should also be checked using
+the ``dts-check-format.sh`` script in the ``devtools`` directory of the DPDK repo.
+To run the script, extra :ref:`Python dependencies <dts_deps>` are needed.
+
 .. _contrib_check_compilation:
 
 Checking Compilation
diff --git a/doc/guides/tools/dts.rst b/doc/guides/tools/dts.rst
index 515b15e4d8..9e8929f567 100644
--- a/doc/guides/tools/dts.rst
+++ b/doc/guides/tools/dts.rst
@@ -54,6 +54,7 @@ DTS uses Poetry as its Python dependency management.
 Python build/development and runtime environments are the same and DTS development environment,
 DTS runtime environment or just plain DTS environment are used interchangeably.
 
+.. _dts_deps:
 
 Setting up DTS environment
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -291,8 +292,15 @@ When adding code to the DTS framework, pay attention to the rest of the code
 and try not to divert much from it.
 The :ref:`DTS developer tools <dts_dev_tools>` will issue warnings
 when some of the basics are not met.
+You should also build the :ref:`API documentation <building_api_docs>`
+to address any issues found during the build.
 
-The code must be properly documented with docstrings.
+The API documentation, which is a helpful reference when developing, may be accessed
+in the code directly or generated with the :ref:`API docs build steps <building_api_docs>`.
+When adding new files or modifying the directory structure,
+the corresponding changes must be made to DTS api doc sources in ``doc/api/dts``.
+
+Speaking of which, the code must be properly documented with docstrings.
 The style must conform to the `Google style
 <https://google.github.io/styleguide/pyguide.html#38-comments-and-docstrings>`_.
 See an example of the style `here
@@ -427,6 +435,35 @@ the DTS code check and format script.
 Refer to the script for usage: ``devtools/dts-check-format.sh -h``.
 
 
+.. _building_api_docs:
+
+Building DTS API docs
+---------------------
+
+The documentation is built using the standard DPDK build system.
+See :doc:`../linux_gsg/build_dpdk` for more details on compiling DPDK with meson.
+
+The :ref:`doc build dependencies <doc_dependencies>` may be installed with Poetry:
+
+.. code-block:: console
+
+   poetry install --no-root --only docs
+   poetry install --no-root --with docs  # an alternative that will also install DTS dependencies
+   poetry shell
+
+After executing the meson command, build the documentation with:
+
+.. code-block:: console
+
+   ninja -C build doc
+
+The output is generated in ``build/doc/api/dts/html``.
+
+.. note::
+
+   Make sure to fix any Sphinx warnings when adding or updating docstrings.
+
+
 Configuration Schema
 --------------------
 
diff --git a/doc/meson.build b/doc/meson.build
index 6f74706aa2..1e0cfa4127 100644
--- a/doc/meson.build
+++ b/doc/meson.build
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright(c) 2018 Luca Boccassi <bluca@debian.org>
 
+doc_source_dir = meson.current_source_dir()
 doc_targets = []
 doc_target_names = []
 subdir('api')
-- 
2.34.1