meson: build docs with meson

Introduce a custom target `html` and a build configuration option
`docs` to build the sphinx html documentation.

Author: jelly

Makefile

@@ -29,13 +29,6 @@ clean:
 distclean: clean
 	rm -rf dist MANIFEST
 
-SPHINXOPTS += -D version=$(VERSION) -D release=$(VERSION)
-sphinx-%: install
-	mkdir $(BUILD_DIR) && cd $(BUILD_DIR) && $(PYTHON) -m sphinx -b $* $(SPHINXOPTS) ../docs $*
-	@echo Output has been generated in $(BUILD_DIR)/$*
-
-doc: sphinx-html
-
 check: build install
 	($(PYTHON) -m pytest src/systemd/test docs $(TESTFLAGS))
 

README.md

@@ -185,9 +185,9 @@ Online documentation can be found at [freedesktop.org](https://www.freedesktop.o
 
 To build it locally run:
 
-    make sphinx-html
+    ninja -C build html
 
-Or use any other builder, see `man sphinx-build` for a list. The compiled docs will be e.g. in `docs/html`.
+Or use any other builder, see `man sphinx-build` for a list. The compiled docs will be e.g. in `build/html`.
 
 Viewing Output
 ==============

meson.build

@@ -40,3 +40,22 @@ test(
 )
 
 alias_target('update-constants', update_constants)
+
+# Docs
+sphinx_build = find_program('sphinx-build', disabler: true, required: get_option('docs'))
+sphinx_args = ['-Dversion=' + meson.project_version(), '-Drelease=' + meson.project_version()]
+
+input_dir = meson.current_source_dir() / 'docs'
+output_dir = meson.current_build_dir() / 'html'
+doc_target = custom_target('html',
+        output: 'html',
+        input: files('docs/conf.py',
+                     'docs/daemon.rst', 'docs/id128.rst',
+                     'docs/journal.rst', 'docs/login.rst',
+                     'docs/layout.html', 'docs/default.css'),
+        command: [sphinx_build, '-b', 'html', sphinx_args, input_dir, output_dir],
+        env: { 'PYTHONPATH': meson.current_build_dir() / 'src' },
+        build_by_default: get_option('docs'),
+        install: get_option('docs'),
+        install_dir: get_option('datadir') / 'doc' / meson.project_name()
+)

meson.options

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+option('docs', type : 'boolean', value : false)