docs: support building a subset of the documentation with build_docs

Closes IDF-1688

docs/build_docs.py

@@ -84,6 +84,8 @@ def main():
                         help="Parallel Sphinx builds - number of independent Sphinx builds to run", default="auto")
     parser.add_argument("--sphinx-parallel-jobs", "-j", choices=["auto"] + [str(x) for x in range(8)],
                         help="Sphinx parallel jobs argument - number of threads for each Sphinx build to use", default="1")
+    parser.add_argument("--input-docs", "-i", nargs='+', default=[""],
+                        help="List of documents to build relative to the doc base folder, i.e. the language folder. Defaults to all documents")
 
     action_parsers = parser.add_subparsers(dest='action')
 
@@ -153,7 +155,7 @@ def parallel_call(args, callback):
     for target in targets:
         for language in languages:
             build_dir = os.path.realpath(os.path.join(args.build_dir, language, target))
-            entries.append((language, target, build_dir, args.sphinx_parallel_jobs, args.builders))
+            entries.append((language, target, build_dir, args.sphinx_parallel_jobs, args.builders, args.input_docs))
 
     print(entries)
     errcodes = pool.map(callback, entries)
@@ -175,7 +177,7 @@ def parallel_call(args, callback):
         return 0
 
 
-def sphinx_call(language, target, build_dir, sphinx_parallel_jobs, buildername):
+def sphinx_call(language, target, build_dir, sphinx_parallel_jobs, buildername, input_docs):
     # Note: because this runs in a multiprocessing Process, everything which happens here should be isolated to a single process
     # (ie it doesn't matter if Sphinx is using global variables, as they're it's own copy of the global variables)
 
@@ -201,6 +203,7 @@ def sphinx_call(language, target, build_dir, sphinx_parallel_jobs, buildername):
             "-w", SPHINX_WARN_LOG,
             "-t", target,
             "-D", "idf_target={}".format(target),
+            "-D", "docs_to_build={}".format(",". join(input_docs)),
             os.path.join(os.path.abspath(os.path.dirname(__file__)), language),  # srcdir for this language
             os.path.join(build_dir, buildername)                    # build directory
             ]
@@ -259,9 +262,9 @@ def action_build(args):
 
 
 def call_build_docs(entry):
-    (language, target, build_dir, sphinx_parallel_jobs, builders) = entry
+    (language, target, build_dir, sphinx_parallel_jobs, builders, input_docs) = entry
     for buildername in builders:
-        ret = sphinx_call(language, target, build_dir, sphinx_parallel_jobs, buildername)
+        ret = sphinx_call(language, target, build_dir, sphinx_parallel_jobs, buildername, input_docs)
         if ret != 0:
             return ret
 

docs/conf_common.py

@@ -383,6 +383,7 @@ def setup(app):
         app.add_config_value('idf_targets', None, 'env')
 
     app.add_config_value('conditional_include_dict', None, 'env')
+    app.add_config_value('docs_to_build', None, 'env')
 
     # Breathe extension variables (depend on build_dir)
     # note: we generate into xml_in and then copy_if_modified to xml dir

docs/en/contribute/add-ons-reference.rst

@@ -167,6 +167,8 @@ Other Extensions
 :idf_file:`docs/idf_extensions/exclude_docs.py`
     Sphinx extension that updates the excluded documents according to the conditional_include_dict {tag:documents}. If the tag is set, then the list of documents will be included.
 
+    Also responsible for excluding documents when building with the config value ``docs_to_build`` set. In these cases all documents not listed in ``docs_to_build`` will be excluded.
+
     Subscribes to ``idf-defines-generated`` as it relies on the sphinx tags to determine which documents to exclude
 
 :idf_file:`docs/idf_extensions/run_doxygen.py`

docs/en/contribute/documenting-code.rst

@@ -511,6 +511,23 @@ Choices for language (``-l``) are ``en`` and ``zh_CN``. Choices for target (``-t
 
 Build documentation will be placed in ``_build/<language>/<target>/html`` folder. To see it, open the ``index.html`` inside this directory in a web browser.
 
+Building a subset of the documentation
+""""""""""""""""""""""""""""""""""""""
+Since building the full documentation can be quite slow, it might be useful to just build just the subset of the documentation you are interested in.
+
+This can be achieved by listing the document you want to build::
+
+    ./build_docs.py -l en -t esp32 -i api-reference/peripherals/can.rst build
+
+Building multiple documents is also possible::
+
+    ./build_docs.py -l en -t esp32 -i api-reference/peripherals/can.rst api-reference/peripherals/adc.rst build
+
+As well as wildcards::
+
+    ./build_docs.py -l en -t esp32 -i api-reference/peripherals/* build
+
+Note that this is a feature intended to simply testing and debugging during writing of documentation. The HTML output won't be perfect, i.e. it will not build a proper index that lists all the documents, and any references to documents that are not built will result in warnings.
 
 Building PDF
 """"""""""""

docs/idf_extensions/exclude_docs.py

@@ -1,10 +1,43 @@
+from sphinx.util import get_matching_files
+from sphinx.util.matching import compile_matchers
+
+
 # Updates the excluded documents according to the conditional_include_dict {tag:documents}
 def update_exclude_patterns(app, config):
+
+    # Default to building all if option not set
+    if config.docs_to_build:
+        build_subset(app, config)
+
     for tag, docs in config.conditional_include_dict.items():
         if not app.tags.has(tag):
             app.config.exclude_patterns.extend(docs)
 
 
+def build_subset(app, config):
+    # Convert to list of docs to build
+    docs_to_build = config.docs_to_build.split(',')
+
+    # Exclude all documents which were not set as docs_to_build when build_docs were called
+    exclude_docs = [filename for filename in get_matching_files(app.srcdir, compile_matchers(docs_to_build))]
+    docs = [filename for filename in get_matching_files(app.srcdir, compile_matchers(exclude_docs))]
+
+    app.config.exclude_patterns.extend(exclude_docs)
+
+    # Get all docs that will be built
+    docs = [filename for filename in get_matching_files(app.srcdir, compile_matchers(exclude_docs))]
+    if not docs:
+        raise ValueError("No documents to build")
+    print("Building a subset of the documents: {}".format(docs))
+
+    # Sphinx requires a master document, if there is a document name 'index' then we pick that
+    index_docs = [doc for doc in docs if 'index' in doc]
+    if index_docs:
+        config.master_doc = index_docs[0].replace('.rst', '')
+    else:
+        config.master_doc = docs[0].replace('.rst', '')
+
+
 def setup(app):
     # Tags are generated together with defines
     app.connect('config-inited', update_exclude_patterns)