Only show GitHub check annotations on changed doc paragraphs

.github/workflows/reusable-docs.yml

@@ -18,6 +18,8 @@ jobs:
     timeout-minutes: 60
     steps:
     - uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
     - name: 'Set up Python'
       uses: actions/setup-python@v4
       with:
@@ -28,13 +30,6 @@ jobs:
       run: make -C Doc/ venv
 
     # To annotate PRs with Sphinx nitpicks (missing references)
-    - name: 'Get list of changed files'
-      if: github.event_name == 'pull_request'
-      id: changed_files
-      uses: Ana06/get-changed-files@v2.2.0
-      with:
-        filter: "Doc/**"
-        format: csv  # works for paths with spaces
     - name: 'Build HTML documentation'
       continue-on-error: true
       run: |
@@ -45,7 +40,7 @@ jobs:
       if: github.event_name == 'pull_request'
       run: |
         python Doc/tools/check-warnings.py \
-          --check-and-annotate '${{ steps.changed_files.outputs.added_modified }}' \
+          --check-and-annotate-changed 'origin/${{ github.base_ref }}' '${{ github.sha }}' \
           --fail-if-regression \
           --fail-if-improved
 

Doc/tools/check-warnings.py

@@ -3,11 +3,13 @@
 Check the output of running Sphinx in nit-picky mode (missing references).
 """
 import argparse
-import csv
+import itertools
 import os
 import re
+import subprocess
 import sys
 from pathlib import Path
+from typing import TextIO
 
 # Exclude these whether they're dirty or clean,
 # because they trigger a rebuild of dirty files.
@@ -24,28 +26,150 @@
     "venv",
 }
 
-PATTERN = re.compile(r"(?P<file>[^:]+):(?P<line>\d+): WARNING: (?P<msg>.+)")
+# Regex pattern to match the parts of a Sphinx warning
+WARNING_PATTERN = re.compile(
+    r"(?P<file>([A-Za-z]:[\\/])?[^:]+):(?P<line>\d+): WARNING: (?P<msg>.+)"
+)
 
+# Regex pattern to match the line numbers in a Git unified diff
+DIFF_PATTERN = re.compile(
+    r"^@@ -(?P<linea>\d+),(?P<removed>\d+) \+(?P<lineb>\d+),(?P<added>\d+) @@",
+    flags=re.MULTILINE,
+)
 
-def check_and_annotate(warnings: list[str], files_to_check: str) -> None:
+
+def get_diff_files(ref_a: str, ref_b: str, filter_mode: str = "") -> set[Path]:
+    """List the files changed between two Gif refs, filtered by change type."""
+    added_files_result = subprocess.run(
+        [
+            "git",
+            "diff",
+            f"--diff-filter={filter_mode}",
+            "--name-only",
+            f"{ref_a}...{ref_b}",
+            "--",
+        ],
+        stdout=subprocess.PIPE,
+        check=True,
+        text=True,
+    )
+
+    added_files = added_files_result.stdout.strip().split("\n")
+    return {Path(file.strip()) for file in added_files if file.strip()}
+
+
+def get_diff_lines(ref_a: str, ref_b: str, file: os.PathLike) -> list[int]:
+    """List the lines changed between two Gif refs for a specific file."""
+    diff_output = subprocess.run(
+        [
+            "git",
+            "diff",
+            "--unified=0",
+            "--diff-filter=M",
+            f"{ref_a}...{ref_b}",
+            "--",
+            str(file),
+        ],
+        stdout=subprocess.PIPE,
+        check=True,
+        text=True,
+    )
+
+    line_matches = DIFF_PATTERN.finditer(diff_output.stdout)
+    line_ints = [
+        (int(line_match["lineb"]), int(line_match["added"]))
+        for line_match in line_matches
+    ]
+    line_ranges = [
+        range(line_b, line_b + added) for line_b, added in line_ints
+    ]
+    line_numbers = list(itertools.chain(*line_ranges))
+    return line_numbers
+
+
+def get_para_line_numbers(file_obj: TextIO) -> list[list[int]]:
+    """Get the line numbers of text in a file object, grouped by paragraph."""
+    paragraphs = []
+    prev_line = None
+    for lineno, line in enumerate(file_obj):
+        lineno = lineno + 1
+        if prev_line is None or (line.strip() and not prev_line.strip()):
+            paragraph = [lineno - 1]
+            paragraphs.append(paragraph)
+        paragraph.append(lineno)
+        prev_line = line
+    return paragraphs
+
+
+def process_touched_warnings(
+    warnings: list[str], ref_a: str, ref_b: str
+) -> list[re.Match]:
+    """Filter a list of Sphinx warnings to those affecting touched lines."""
+    added_files, modified_files = tuple(
+        get_diff_files(ref_a, ref_b, filter_mode=mode) for mode in ("A", "M")
+    )
+
+    warnings_added, warnings_modified = tuple(
+        [
+            WARNING_PATTERN.fullmatch(warning.strip())
+            for warning in warnings
+            if any(str(file) in warning for file in files)
+        ]
+        for files in (added_files, modified_files)
+    )
+    warnings_added, warnings_modified = tuple(
+        [warning for warning in warning_matches if warning]
+        for warning_matches in (warnings_added, warnings_modified)
+    )
+
+    modified_files_warned = {
+        file
+        for file in modified_files
+        if any(str(file) in warning["file"] for warning in warnings_modified)
+    }
+
+    warnings_touched = warnings_added.copy()
+    for file in modified_files_warned:
+        diff_lines = get_diff_lines(ref_a, ref_b, file)
+        with file.open(encoding="UTF-8") as file_obj:
+            paragraphs = get_para_line_numbers(file_obj)
+        touched_paras = [
+            para_lines
+            for para_lines in paragraphs
+            if set(diff_lines) & set(para_lines)
+        ]
+        touched_para_lines = set(itertools.chain(*touched_paras))
+        warnings_infile = [
+            warning
+            for warning in warnings_modified
+            if str(file) in warning["file"]
+        ]
+        warnings_touched += [
+            warning
+            for warning in warnings_infile
+            if int(warning["line"]) in touched_para_lines
+        ]
+
+    return warnings_touched
+
+
+def check_and_annotate_changed(
+    warnings: list[str], ref_a: str = "main", ref_b: str = "HEAD"
+) -> None:
     """
-    Convert Sphinx warning messages to GitHub Actions.
+    Convert Sphinx warning messages to GitHub Actions for changed paragraphs.
 
     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:
+    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))
+    warnings_touched = process_touched_warnings(warnings, ref_a, ref_b)
+    for warning in warnings_touched:
+        print("::warning file={file},line={line}::{msg}".format_map(warning))
 
 
 def fail_if_regression(
@@ -68,7 +192,7 @@ def fail_if_regression(
             print(filename)
             for warning in warnings:
                 if filename in warning:
-                    if match := PATTERN.fullmatch(warning):
+                    if match := WARNING_PATTERN.fullmatch(warning):
                         print("  {line}: {msg}".format_map(match))
         return -1
     return 0
@@ -94,9 +218,10 @@ def fail_if_improved(
 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",
+        "--check-and-annotate-changed",
+        nargs=2,
+        help="Annotate lines changed between two refs "
+        "with warnings on GitHub Actions",
     )
     parser.add_argument(
         "--fail-if-regression",
@@ -114,7 +239,7 @@ def main() -> int:
     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:
+    with Path("Doc/sphinx-warnings.txt").open(encoding="UTF-8") as f:
         warnings = f.read().splitlines()
 
     cwd = str(Path.cwd()) + os.path.sep
@@ -131,8 +256,8 @@ def main() -> int:
             if filename.strip() and not filename.startswith("#")
         }
 
-    if args.check_and_annotate:
-        check_and_annotate(warnings, args.check_and_annotate)
+    if args.check_and_annotate_changed:
+        check_and_annotate_changed(warnings, *args.check_and_annotate_changed)
 
     if args.fail_if_regression:
         exit_code += fail_if_regression(