[3.12] gh-101100: Docs: Check Sphinx warnings and fail if improved (GH-106460) (#108116)

* gh-101100: Docs: Check Sphinx warnings and fail if improved (#106460)

(cherry picked from commit 806d7c98a5)

* [3.12] gh-101100: Docs: Check Sphinx warnings and fail if improved (GH-106460).
(cherry picked from commit 806d7c98a5)

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

---------

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

Doc/tools/check-warnings.py

@@ -0,0 +1,149 @@
+#!/usr/bin/env python3
+"""
+Check the output of running Sphinx in nit-picky mode (missing references).
+"""
+import argparse
+import csv
+import os
+import re
+import sys
+from pathlib import Path
+
+# Exclude these whether they're dirty or clean,
+# because they trigger a rebuild of dirty files.
+EXCLUDE_FILES = {
+    "Doc/whatsnew/changelog.rst",
+}
+
+# Subdirectories of Doc/ to exclude.
+EXCLUDE_SUBDIRS = {
+    ".env",
+    ".venv",
+    "env",
+    "includes",
+    "venv",
+}
+
+PATTERN = re.compile(r"(?P<file>[^:]+):(?P<line>\d+): WARNING: (?P<msg>.+)")
+
+
+def check_and_annotate(warnings: list[str], files_to_check: str) -> None:
+    """
+    Convert Sphinx warning messages to GitHub Actions.
+
+    Converts lines like:
+        .../Doc/library/cgi.rst:98: WARNING: reference target not found
+    to:
+        ::warning file=.../Doc/library/cgi.rst,line=98::reference target not found
+
+    Non-matching lines are echoed unchanged.
+
+    see:
+    https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-a-warning-message
+    """
+    files_to_check = next(csv.reader([files_to_check]))
+    for warning in warnings:
+        if any(filename in warning for filename in files_to_check):
+            if match := PATTERN.fullmatch(warning):
+                print("::warning file={file},line={line}::{msg}".format_map(match))
+
+
+def fail_if_regression(
+    warnings: list[str], files_with_expected_nits: set[str], files_with_nits: set[str]
+) -> int:
+    """
+    Ensure some files always pass Sphinx nit-picky mode (no missing references).
+    These are files which are *not* in .nitignore.
+    """
+    all_rst = {
+        str(rst)
+        for rst in Path("Doc/").rglob("*.rst")
+        if rst.parts[1] not in EXCLUDE_SUBDIRS
+    }
+    should_be_clean = all_rst - files_with_expected_nits - EXCLUDE_FILES
+    problem_files = sorted(should_be_clean & files_with_nits)
+    if problem_files:
+        print("\nError: must not contain warnings:\n")
+        for filename in problem_files:
+            print(filename)
+            for warning in warnings:
+                if filename in warning:
+                    if match := PATTERN.fullmatch(warning):
+                        print("  {line}: {msg}".format_map(match))
+        return -1
+    return 0
+
+
+def fail_if_improved(
+    files_with_expected_nits: set[str], files_with_nits: set[str]
+) -> int:
+    """
+    We may have fixed warnings in some files so that the files are now completely clean.
+    Good news! Let's add them to .nitignore to prevent regression.
+    """
+    files_with_no_nits = files_with_expected_nits - files_with_nits
+    if files_with_no_nits:
+        print("\nCongratulations! You improved:\n")
+        for filename in sorted(files_with_no_nits):
+            print(filename)
+        print("\nPlease remove from Doc/tools/.nitignore\n")
+        return -1
+    return 0
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--check-and-annotate",
+        help="Comma-separated list of files to check, "
+        "and annotate those with warnings on GitHub Actions",
+    )
+    parser.add_argument(
+        "--fail-if-regression",
+        action="store_true",
+        help="Fail if known-good files have warnings",
+    )
+    parser.add_argument(
+        "--fail-if-improved",
+        action="store_true",
+        help="Fail if new files with no nits are found",
+    )
+    args = parser.parse_args()
+    exit_code = 0
+
+    wrong_directory_msg = "Must run this script from the repo root"
+    assert Path("Doc").exists() and Path("Doc").is_dir(), wrong_directory_msg
+
+    with Path("Doc/sphinx-warnings.txt").open() as f:
+        warnings = f.read().splitlines()
+
+    cwd = str(Path.cwd()) + os.path.sep
+    files_with_nits = {
+        warning.removeprefix(cwd).split(":")[0]
+        for warning in warnings
+        if "Doc/" in warning
+    }
+
+    with Path("Doc/tools/.nitignore").open() as clean_files:
+        files_with_expected_nits = {
+            filename.strip()
+            for filename in clean_files
+            if filename.strip() and not filename.startswith("#")
+        }
+
+    if args.check_and_annotate:
+        check_and_annotate(warnings, args.check_and_annotate)
+
+    if args.fail_if_regression:
+        exit_code += fail_if_regression(
+            warnings, files_with_expected_nits, files_with_nits
+        )
+
+    if args.fail_if_improved:
+        exit_code += fail_if_improved(files_with_expected_nits, files_with_nits)
+
+    return exit_code
+
+
+if __name__ == "__main__":
+    sys.exit(main())