Improve php-src docs sphinx build, also on *nix (phpGH-16743)

* Document .rst file maximum line length of 100

In 19d2b84 ("Create book for docs", 2024-01-30) the build of the
php-src documentation has been introduced.

It is based on reStructuredText (rst) [Docutils] for its source files,
this stems from the sphinx-build utility in use to build the static HTML
pages of the php-src documentation.

The maximum line length of these text files has been set to 100
characters in 19d2b84 ("Create book for docs", 2024-01-30), the
rationale is unknown to the documenting author at time of writing this
message.

This formatting constraint is applied with the rstfmt utility [rstfmt]
via its invocation (documented in CI build instructions and README.md:)

    rstfmt -w 100 source

The `-w, --width` option takes a WIDTH argument that is "the
target line length in characters" (cf. `rstfmt --help`.)

There is also an `--ext EXT` argument option, that is "the extension of
files to look at when passed a directory" ("source" is the name of
a directory in the invocation above) and defaults to "rst".

Henceforth, the editor configuration [EditorConfig] can benefit from
documenting this expectation in the repositories .editorconfig file,
which has been introduced already earlier in 5c38fbe ("Added
editorconfig file", 2016-06-26).

[Docutils]: https://docutils.sourceforge.io/index.html "Docutils: Documentation Utilities — Written in Python, for General- and Special-Purpose Use"
[rstfmt]: https://github.com/dzhu/rstfmt "A formatter for reStructuredText"
[EditorConfig]: https://editorconfig.org/ "EditorConfig helps maintain consistent coding styles for multiple developers working on the same project across various editors and IDEs"

* Makefile for php-src docs build

In 19d2b84 ("Create book for docs", 2024-01-30) the php-src
documentation (php-src docs) build has been introduced, yet the build
instructions, namely `make html`, did not yield the expected results
within the parenting setup of the php-src project on *nix systems.

The reason is that the `make html` build instruction does not execute
the make.bat file which contains the recipe to build the static HTML
pages.

It is an unused leftover file from initializing the project with
sphinx-quickstart. [1]

Removing it in and adding a Makefile suffices to recover the build of
php-src ./docs on a *nix system.

Formatting constraints checked in the docs workflow in CI update
use the make file to make sure the commands stay consistent and the
build is managed by the build manager.

[1]: https://www.sphinx-doc.org/en/master/man/sphinx-quickstart.html "sphinx-quickstart is an interactive tool that asks some questions about your project and then generates a complete documentation directory and sample Makefile to be used with sphinx-build(1)."

* Bind requirements.txt for php-src docs build

Define the required packages to install for the php-src docs build in
the docs/requirements.txt file:

1) Sphinx
2) sphinx-design
3) sphinxawesome-theme
4) rstfmt

This should also later on ease the use of a requirements_frozen.txt
file to pin the build dependencies if needed/wanted.

Additionally, some formatting corrections in README.md (based on the
profile in .editorconfig) as well as adding the recommendation to use
a Python virtual environment. Python3 and Pip were already named, and
with Python3 there is the venv module (Python 3.3; Sep 2012) to manage
these so-called python virtual environments [venv], which are commonly
a preferred way to install dependencies within development projects
and build systems.

[venv]: https://docs.python.org/3/library/venv.html "venv — Creation of virtual environments — Python documentation"

* Remove deprecated theme configuration

For the configured Awesome Sphinx Theme [1] highlighting extension, the
sphinx-build currently yields the following diagnostics:

     WARNING: while setting up extension sphinxawesome_theme.highlighting: \
     You no longer have to include the `sphinxawsome_theme.highlighting` \
     extension. This extension will be removed in the next major release.

(via `make html`, the configuration file is `source/conf.py`.)

The diagnostic message was introduced by sphinxawesome-theme 5.2.0,
  released May 31, 2024. [2], [3]

Removing the extension from the list of extensions in the configuration
file levitates.

No changes to requirements.txt, the extension was transitive as bundled
by the Awesome Sphinx Theme [1], and 5.2.0 deprecates it with the new
feature to "Support `pygments_style_dark` option that allows you to set
a different syntax highlighting scheme in light and dark modes." [3]

[1]: https://sphinxawesome.xyz/ "Awesome Sphinx Theme — Create functional and beautiful websites for your documentation with Sphinx."
[2]: https://pypi.org/project/sphinxawesome-theme/5.2.0/#history
[3]: https://github.com/kai687/sphinxawesome-theme/releases/tag/5.2.0

.editorconfig

@@ -32,3 +32,7 @@ max_line_length          = 80
 
 [*.patch]
 trim_trailing_whitespace = false
+
+[*.rst]
+indent_style             = space
+max_line_length          = 100

.github/workflows/docs.yml

@@ -19,9 +19,9 @@ jobs:
       - name: git checkout
         uses: actions/checkout@v4
       - name: Install dependencies
-        run: pip install sphinx-design sphinxawesome-theme rstfmt
+        run: pip install -r docs/requirements.txt
       - name: Check formatting
-        run: rstfmt --check -w 100 docs/source
+        run: make -C docs check-formatting
       - name: Publish
         if: github.event_name == 'push'
         uses: sphinx-notes/pages@v3

docs/Makefile

@@ -0,0 +1,36 @@
+# Makefile for php-src/docs
+# Copyright (c) The PHP Group
+
+# If people set these on the make command line, use 'em
+
+SPHINXBUILD ?= sphinx-build
+
+SOURCEDIR = source
+BUILDDIR = build
+RSTFMT = rstfmt
+RSTFMTFLAGS = -w 100
+
+rwildcard = $(foreach d,$(wildcard $(1:=/*)),$(call rwildcard,$d,$2) $(filter $(subst *,%,$2),$d))
+FILES = $(call rwildcard,$(SOURCEDIR),*.rst)
+
+all : html
+
+.PHONY : check-formatting clean html preflight
+.SUFFIXES : # Disable legacy behavior
+
+check-formatting :
+	$(RSTFMT) $(RSTFMTFLAGS) --check $(SOURCEDIR)
+
+clean :
+	rm -rf -- $(wildcard $(SOURCEDIR)/.~ $(BUILDDIR))
+
+html : preflight
+	$(SPHINXBUILD) -M $@ $(SOURCEDIR) $(BUILDDIR)
+	@printf 'Browse the \e]8;;%s\e\\%s\e]8;;\e\\.\n' \
+		"file://$(abspath $(BUILDDIR))/$@/index.$@" "php-src html docs locally"
+
+preflight : $(SOURCEDIR)/.~
+
+$(SOURCEDIR)/.~ : $(FILES)
+	$(RSTFMT) $(RSTFMTFLAGS) $?
+	touch $@

docs/README.md

@@ -1,9 +1,10 @@
 # php-src docs
 
 This is the home of the php-src internal documentation, hosted at
-[php.github.io/php-src/](https://php.github.io/php-src/). It is in very early stages, but is
-intended to become the primary place where new information about php-src is documented. Over time,
-it is expected to replace various mediums like:
+[php.github.io/php-src/](https://php.github.io/php-src/). It is in very early
+stages, but is intended to become the primary place where new information about
+php-src is documented. Over time, it is expected to replace various mediums
+like:
 
 * https://www.phpinternalsbook.com/
 * https://wiki.php.net/internals
@@ -14,11 +15,15 @@ it is expected to replace various mediums like:
 `python` 3 and `pip` are required.
 
 ```bash
-pip install sphinx sphinx-design sphinxawesome-theme
+cd docs
+# Recommended: Initialize and activate a Python virtual environment
+pip install --upgrade pip
+pip install -r requirements.txt
 make html
 ```
 
-That's it! You can view the documentation under `./build/html/index.html` in your browser.
+That's it! You can view the documentation under `./build/html/index.html` in
+your browser.
 
 ## Formatting
 
@@ -29,5 +34,5 @@ The files in this documentation are formatted using the
 rstfmt -w 100 source
 ```
 
-This tool is not perfect. It breaks on custom directives, so we might switch to either a fork or
-something else in the future.
+This tool is not perfect. It breaks on custom directives, so we might switch to
+either a fork or something else in the future.

docs/requirements.txt

@@ -0,0 +1,4 @@
+Sphinx
+sphinx-design
+sphinxawesome-theme
+rstfmt

docs/source/conf.py

@@ -16,7 +16,6 @@
 author = 'The PHP Group'
 extensions = [
     'sphinx_design',
-    'sphinxawesome_theme.highlighting',
 ]
 templates_path = ['_templates']
 html_theme = 'sphinxawesome_theme'