chore: Run clang_tidy_check with pass_filenames: false from pre-commit (#7800)

.cspell.config.yaml

@@ -65,6 +65,7 @@ words:
   - Btrfs
   - Buildx
   - canonicality
+  - canonicalised
   - changespq
   - checkme
   - choco

.pre-commit-config.yaml

@@ -32,6 +32,11 @@ repos:
         # as standalone translation units, so they have no compile_commands.json
         # entry to lint (verify_headers checks them transitively).
         exclude: '^include/xrpl/protocol_autogen|\.ipp$'
+        # run-clang-tidy --fix may edit headers included by files it is not run on,
+        # so pre-commit must not split the files across parallel hook invocations.
+        # The script determines the staged files itself and lets run-clang-tidy
+        # handle parallelism internally.
+        pass_filenames: false
       - id: fix-include-style
         name: fix include style
         entry: ./bin/pre-commit/fix_include_style.py

bin/pre-commit/clang_tidy_check.py

@@ -1,27 +1,46 @@
 #!/usr/bin/env python3
-"""Pre-commit hook that runs clang-tidy on changed files using run-clang-tidy.
+"""Pre-commit hook that runs clang-tidy on staged files using run-clang-tidy.
 
-The set of files is chosen by pre-commit (see .pre-commit-config.yaml), which
-filters to C/C++ sources and excludes `.ipp` fragments. Headers are linted
-directly: the `verify_headers` build option (ON by default) compiles every
-`.h`/`.hpp` on its own, so each header is the main file of its own
-compile_commands.json entry and run-clang-tidy can analyse it just like a
-`.cpp`.
+The script determines the staged files itself (see `pass_filenames: false` in
+.pre-commit-config.yaml) so run-clang-tidy is run once and handles parallelism
+internally: pre-commit would otherwise split the files across parallel hook
+invocations that race when fixes edit a shared header.
+
+Fixes are collected with `-export-fixes` and applied by clang-apply-replacements
+in a separate step rather than with run-clang-tidy's `-fix`. The `add_module`
+build isolates each module's headers behind a per-module symlink directory
+(build/modules/<module>/...), so a header reachable from several translation
+units is referenced through different paths that all resolve to the same source
+file. clang-apply-replacements deduplicates identical replacements by their
+literal path, so those paths must be canonicalised to the real source path
+first; otherwise the same fix is applied once per path and corrupts the header.
 """
 
 from __future__ import annotations
 
 import os
+import re
 import shutil
 import subprocess
 import sys
+import tempfile
 from pathlib import Path
 
 CLANG_TIDY_VERSION = 22
 
+# Extensions run-clang-tidy can analyse: `.cpp` translation units and, thanks to
+# the `verify_headers` build option, `.h`/`.hpp` headers (each has its own
+# compile_commands.json entry). `.ipp` fragments have no entry and are skipped.
+TIDY_EXTENSIONS = {".cpp", ".h", ".hpp"}
 
-def find_run_clang_tidy() -> str | None:
-    for candidate in (f"run-clang-tidy-{CLANG_TIDY_VERSION}", "run-clang-tidy"):
+# A single-quoted `FilePath:` entry in an -export-fixes YAML file, allowing the
+# `- ` marker that precedes it inside a `Replacements:` sequence. clang-tidy
+# emits paths single-quoted and doubles any embedded quote per YAML rules.
+FILEPATH_RE = re.compile(r"^(\s*(?:-\s+)?FilePath:\s*)'((?:[^']|'')*)'\s*$")
+
+
+def find_tool(name: str) -> str | None:
+    for candidate in (f"{name}-{CLANG_TIDY_VERSION}", name):
         if path := shutil.which(candidate):
             return path
     return None
@@ -35,23 +54,43 @@ def find_build_dir(repo_root: Path) -> Path | None:
     return None
 
 
+def staged_files(repo_root: Path) -> list[Path]:
+    """Return absolute paths of staged, lint-able C/C++ files.
+
+    `--diff-filter=d` excludes deletions so we never lint a removed file.
+    """
+    output = subprocess.check_output(
+        ["git", "diff", "--staged", "--name-only", "--diff-filter=d", "--"]
+        + [f"*{ext}" for ext in TIDY_EXTENSIONS],
+        text=True,
+        cwd=repo_root,
+    )
+    return [repo_root / rel for rel in output.splitlines() if rel]
+
+
+def canonicalize_fix_paths(fixes_dir: Path) -> None:
+    """Rewrite every `FilePath` in the exported fixes to its real source path.
+
+    A header included through a module's isolation symlink is recorded under that
+    symlink's path; collapsing all paths to the same real file lets
+    clang-apply-replacements recognise the per-translation-unit duplicates and
+    apply each fix once.
+    """
+    for yaml in fixes_dir.glob("*.yaml"):
+        lines = []
+        for line in yaml.read_text().splitlines():
+            if m := FILEPATH_RE.match(line):
+                path = m.group(2).replace("''", "'")
+                real = os.path.realpath(path).replace("'", "''")
+                line = f"{m.group(1)}'{real}'"
+            lines.append(line)
+        yaml.write_text("\n".join(lines) + "\n")
+
+
 def main():
     if not os.environ.get("TIDY"):
         return 0
 
-    files = sys.argv[1:]
-    if not files:
-        return 0
-
-    run_clang_tidy = find_run_clang_tidy()
-    if not run_clang_tidy:
-        print(
-            f"clang-tidy check failed: TIDY is enabled but neither "
-            f"'run-clang-tidy-{CLANG_TIDY_VERSION}' nor 'run-clang-tidy' was found in PATH.",
-            file=sys.stderr,
-        )
-        return 1
-
     repo_root = Path(
         subprocess.check_output(
             ["git", "rev-parse", "--show-toplevel"],
@@ -59,6 +98,29 @@ def main():
             text=True,
         ).strip()
     )
+
+    files = staged_files(repo_root)
+    if not files:
+        return 0
+
+    run_clang_tidy = find_tool("run-clang-tidy")
+    clang_apply_replacements = find_tool("clang-apply-replacements")
+    missing = [
+        name
+        for name, path in (
+            ("run-clang-tidy", run_clang_tidy),
+            ("clang-apply-replacements", clang_apply_replacements),
+        )
+        if not path
+    ]
+    if missing:
+        print(
+            f"clang-tidy check failed: TIDY is enabled but {' and '.join(missing)} "
+            f"was not found in PATH (tried the '-{CLANG_TIDY_VERSION}' suffix too).",
+            file=sys.stderr,
+        )
+        return 1
+
     build_dir = find_build_dir(repo_root)
     if not build_dir:
         print(
@@ -68,11 +130,23 @@ def main():
         )
         return 1
 
-    result = subprocess.run(
-        [run_clang_tidy, "-quiet", "-p", str(build_dir), "-fix", "-allow-no-checks"]
-        + files
-    )
-    return result.returncode
+    with tempfile.TemporaryDirectory() as fixes_dir:
+        result = subprocess.run(
+            [
+                run_clang_tidy,
+                "-quiet",
+                "-p",
+                build_dir,
+                "-export-fixes",
+                fixes_dir,
+                "-allow-no-checks",
+            ]
+            + files
+        )
+        canonicalize_fix_paths(Path(fixes_dir))
+        applied = subprocess.run([clang_apply_replacements, fixes_dir])
+
+    return result.returncode or applied.returncode
 
 
 if __name__ == "__main__":