Pull in llvm-project's clang-format check action

This action and scripting was written by @tru for LLVM and addresses
some of the false positives we've been seeing in our action. There is
more room for improvement, but it would be better to unify than to have
divergent approaches since we're solving the same problem.

.github/workflows/clang-format-checker.yml

@@ -1,38 +1,54 @@
-name: 'PR clang-format checker'
-on:
-  pull_request_target:
-    types:
-      - opened
-      - edited
-      - synchronize
-      - reopened
+name: "Check code formatting"
+on: pull_request_target
+permissions:
+  pull-requests: write
+
 jobs:
-  check-pr-formatting:
-    permissions:
-      contents: read
-      pull-requests: write
-      checks: write
+  code_formatter:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - name: Fetch LLVM sources
+        uses: actions/checkout@v4
         with:
-          fetch-depth: 0
-      - name: Comparing PR against target branch
+          fetch-depth: 2
+
+      - name: Get changed files
+        id: changed-files
+        uses: tj-actions/changed-files@v39
+        with:
+          separator: ","
+          fetch_depth: 100 # Fetches only the last 10 commits
+
+      - name: "Listed files"
+        run: |
+          echo "Formatting files:"
+          echo "${{ steps.changed-files.outputs.all_changed_files }}"
+
+      - name: Install clang-format
+        uses: aminya/setup-cpp@v1
+        with:
+          clangformat: 17.0.1
+
+      - name: Setup Python env
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+          cache: 'pip'
+          cache-dependency-path: 'utils/git/requirements_formatting.txt'
+
+      - name: Install python dependencies
+        run: pip install -r utils/git/requirements_formatting.txt
+
+      - name: Run code formatter
         env:
-          PR_NUMBER: ${{ github.event.number }}
-          GH_TOKEN: ${{ github.token }}
+          GITHUB_PR_NUMBER: ${{ github.event.pull_request.number }}
+          START_REV: ${{ github.event.pull_request.base.sha }}
+          END_REV: ${{ github.event.pull_request.head.sha }}
+          CHANGED_FILES: ${{ steps.changed-files.outputs.all_changed_files }}
         run: |
-            echo Comparing $PR_NUMBER vs target branch
-            git fetch origin refs/pull/$PR_NUMBER/head:pull/$PR_NUMBER
-            git checkout pull/$PR_NUMBER
-            git diff -U0 --no-color $GITHUB_SHA..pull/$PR_NUMBER | clang-format-diff-15 -p1 | tee format.diff
-            if [ -s format.diff ]
-            then
-              echo PR contains clang-format violations. First 50 lines of the diff: >> message.txt
-              echo \`\`\`diff >> message.txt
-              cat format.diff | head -n 50 >> message.txt
-              echo \`\`\` >> message.txt
-              echo See [action log]\(https://github.com/microsoft/DirectXShaderCompiler/actions/runs/$GITHUB_RUN_ID/\) for the full diff.  >> message.txt
-              gh pr comment $PR_NUMBER --body-file message.txt
-              exit 1
-            fi
+          python utils/git/code-format-helper.py \
+            --token ${{ secrets.GITHUB_TOKEN }} \
+            --issue-number $GITHUB_PR_NUMBER \
+            --start-rev $START_REV \
+            --end-rev $END_REV \
+            --changed-files "$CHANGED_FILES"

utils/git/code-format-helper.py

@@ -0,0 +1,233 @@
+#!/usr/bin/env python3
+#
+# ====- code-format-helper, runs code formatters from the ci --*- python -*--==#
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+# ==-------------------------------------------------------------------------==#
+
+import argparse
+import os
+import subprocess
+import sys
+from functools import cached_property
+
+import github
+from github import IssueComment, PullRequest
+
+
+class FormatHelper:
+    COMMENT_TAG = "<!--LLVM CODE FORMAT COMMENT: {fmt}-->"
+    name = "unknown"
+
+    @property
+    def comment_tag(self) -> str:
+        return self.COMMENT_TAG.replace("fmt", self.name)
+
+    def format_run(self, changed_files: [str], args: argparse.Namespace) -> str | None:
+        pass
+
+    def pr_comment_text(self, diff: str) -> str:
+        return f"""
+{self.comment_tag}
+
+:warning: {self.friendly_name}, {self.name} found issues in your code. :warning:
+
+<details>
+<summary>
+You can test this locally with the following command:
+</summary>
+
+``````````bash
+{self.instructions}
+``````````
+
+</details>
+
+<details>
+<summary>
+View the diff from {self.name} here.
+</summary>
+
+``````````diff
+{diff}
+``````````
+
+</details>
+"""
+
+    def find_comment(
+        self, pr: PullRequest.PullRequest
+    ) -> IssueComment.IssueComment | None:
+        for comment in pr.as_issue().get_comments():
+            if self.comment_tag in comment.body:
+                return comment
+        return None
+
+    def update_pr(self, diff: str, args: argparse.Namespace):
+        repo = github.Github(args.token).get_repo(args.repo)
+        pr = repo.get_issue(args.issue_number).as_pull_request()
+
+        existing_comment = self.find_comment(pr)
+        pr_text = self.pr_comment_text(diff)
+
+        if existing_comment:
+            existing_comment.edit(pr_text)
+        else:
+            pr.as_issue().create_comment(pr_text)
+
+    def update_pr_success(self, args: argparse.Namespace):
+        repo = github.Github(args.token).get_repo(args.repo)
+        pr = repo.get_issue(args.issue_number).as_pull_request()
+
+        existing_comment = self.find_comment(pr)
+        if existing_comment:
+            existing_comment.edit(
+                f"""
+{self.comment_tag}
+:white_check_mark: With the latest revision this PR passed the {self.friendly_name}.
+"""
+            )
+
+    def run(self, changed_files: [str], args: argparse.Namespace):
+        diff = self.format_run(changed_files, args)
+        if diff:
+            self.update_pr(diff, args)
+            return False
+        else:
+            self.update_pr_success(args)
+            return True
+
+
+class ClangFormatHelper(FormatHelper):
+    name = "clang-format"
+    friendly_name = "C/C++ code formatter"
+
+    @property
+    def instructions(self):
+        return " ".join(self.cf_cmd)
+
+    @cached_property
+    def libcxx_excluded_files(self):
+        with open("libcxx/utils/data/ignore_format.txt", "r") as ifd:
+            return [excl.strip() for excl in ifd.readlines()]
+
+    def should_be_excluded(self, path: str) -> bool:
+        if path in self.libcxx_excluded_files:
+            print(f"Excluding file {path}")
+            return True
+        return False
+
+    def filter_changed_files(self, changed_files: [str]) -> [str]:
+        filtered_files = []
+        for path in changed_files:
+            _, ext = os.path.splitext(path)
+            if ext in (".cpp", ".c", ".h", ".hpp", ".hxx", ".cxx"):
+                if not self.should_be_excluded(path):
+                    filtered_files.append(path)
+        return filtered_files
+
+    def format_run(self, changed_files: [str], args: argparse.Namespace) -> str | None:
+        cpp_files = self.filter_changed_files(changed_files)
+        if not cpp_files:
+            return
+        cf_cmd = [
+            "git-clang-format",
+            "--diff",
+            args.start_rev,
+            args.end_rev,
+            "--",
+        ] + cpp_files
+        print(f"Running: {' '.join(cf_cmd)}")
+        self.cf_cmd = cf_cmd
+        proc = subprocess.run(cf_cmd, capture_output=True)
+
+        # formatting needed
+        if proc.returncode == 1:
+            return proc.stdout.decode("utf-8")
+
+        return None
+
+
+class DarkerFormatHelper(FormatHelper):
+    name = "darker"
+    friendly_name = "Python code formatter"
+
+    @property
+    def instructions(self):
+        return " ".join(self.darker_cmd)
+
+    def filter_changed_files(self, changed_files: [str]) -> [str]:
+        filtered_files = []
+        for path in changed_files:
+            name, ext = os.path.splitext(path)
+            if ext == ".py":
+                filtered_files.append(path)
+
+        return filtered_files
+
+    def format_run(self, changed_files: [str], args: argparse.Namespace) -> str | None:
+        py_files = self.filter_changed_files(changed_files)
+        if not py_files:
+            return
+        darker_cmd = [
+            "darker",
+            "--check",
+            "--diff",
+            "-r",
+            f"{args.start_rev}..{args.end_rev}",
+        ] + py_files
+        print(f"Running: {' '.join(darker_cmd)}")
+        self.darker_cmd = darker_cmd
+        proc = subprocess.run(darker_cmd, capture_output=True)
+
+        # formatting needed
+        if proc.returncode == 1:
+            return proc.stdout.decode("utf-8")
+
+        return None
+
+
+ALL_FORMATTERS = (DarkerFormatHelper(), ClangFormatHelper())
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--token", type=str, required=True, help="GitHub authentiation token"
+    )
+    parser.add_argument(
+        "--repo",
+        type=str,
+        default=os.getenv("GITHUB_REPOSITORY", "llvm/llvm-project"),
+        help="The GitHub repository that we are working with in the form of <owner>/<repo> (e.g. llvm/llvm-project)",
+    )
+    parser.add_argument("--issue-number", type=int, required=True)
+    parser.add_argument(
+        "--start-rev",
+        type=str,
+        required=True,
+        help="Compute changes from this revision.",
+    )
+    parser.add_argument(
+        "--end-rev", type=str, required=True, help="Compute changes to this revision"
+    )
+    parser.add_argument(
+        "--changed-files",
+        type=str,
+        help="Comma separated list of files that has been changed",
+    )
+
+    args = parser.parse_args()
+
+    changed_files = []
+    if args.changed_files:
+        changed_files = args.changed_files.split(",")
+
+    exit_code = 0
+    for fmt in ALL_FORMATTERS:
+        if not fmt.run(changed_files, args):
+            exit_code = 1
+
+    sys.exit(exit_code)

utils/git/requirements_formatting.txt

@@ -0,0 +1,52 @@
+#
+# This file is autogenerated by pip-compile with Python 3.11
+# by the following command:
+#
+#    pip-compile --output-file=llvm/utils/git/requirements_formatting.txt llvm/utils/git/requirements_formatting.txt.in
+#
+black==23.9.1
+    # via
+    #   -r llvm/utils/git/requirements_formatting.txt.in
+    #   darker
+certifi==2023.7.22
+    # via requests
+cffi==1.15.1
+    # via
+    #   cryptography
+    #   pynacl
+charset-normalizer==3.2.0
+    # via requests
+click==8.1.7
+    # via black
+cryptography==41.0.3
+    # via pyjwt
+darker==1.7.2
+    # via -r llvm/utils/git/requirements_formatting.txt.in
+deprecated==1.2.14
+    # via pygithub
+idna==3.4
+    # via requests
+mypy-extensions==1.0.0
+    # via black
+packaging==23.1
+    # via black
+pathspec==0.11.2
+    # via black
+platformdirs==3.10.0
+    # via black
+pycparser==2.21
+    # via cffi
+pygithub==1.59.1
+    # via -r llvm/utils/git/requirements_formatting.txt.in
+pyjwt[crypto]==2.8.0
+    # via pygithub
+pynacl==1.5.0
+    # via pygithub
+requests==2.31.0
+    # via pygithub
+toml==0.10.2
+    # via darker
+urllib3==2.0.4
+    # via requests
+wrapt==1.15.0
+    # via deprecated

utils/git/requirements_formatting.txt.in

@@ -0,0 +1,3 @@
+black~=23.0
+darker==1.7.2
+PyGithub==1.59.1