fix(pr-bot): classify renames of core paths as core

.github/workflows/auto-merge.yml

@@ -68,7 +68,10 @@ jobs:
           REPO: ${{ github.repository }}
           PR: ${{ github.event.pull_request.number }}
         run: |
-          gh pr view "$PR" --repo "$REPO" --json files --jq '.files[].path' > changed.txt
+          # REST files endpoint carries previous_filename on renames; the
+          # GraphQL-backed `gh pr view --json files` shortcut does not.
+          gh api "repos/$REPO/pulls/$PR/files" --paginate > files.json
+          PYTHONPATH=src python -m vouch.pr_bot changed-files --json-file files.json > changed.txt
           klass=$(PYTHONPATH=src python -m vouch.pr_bot classify --files-file changed.txt --print-klass)
           echo "klass=$klass" >> "$GITHUB_OUTPUT"
 

.github/workflows/comment-command.yml

@@ -50,7 +50,10 @@ jobs:
           REPO: ${{ github.repository }}
           PR: ${{ github.event.issue.number }}
         run: |
-          gh pr view "$PR" --repo "$REPO" --json files --jq '.files[].path' > changed.txt
+          # REST files endpoint carries previous_filename on renames; the
+          # GraphQL-backed `gh pr view --json files` shortcut does not.
+          gh api "repos/$REPO/pulls/$PR/files" --paginate > files.json
+          PYTHONPATH=src python -m vouch.pr_bot changed-files --json-file files.json > changed.txt
           klass="$(PYTHONPATH=src python -m vouch.pr_bot classify --files-file changed.txt --print-klass)"
           # mark authorized (visible, and enables deauthorize-on-push). a label
           # added via GITHUB_TOKEN does not re-trigger auto-merge.yml (GitHub's

.github/workflows/trust-gate.yml

@@ -20,10 +20,14 @@ jobs:
       - name: list changed files
         env:
           GH_TOKEN: ${{ github.token }}
+          REPO: ${{ github.repository }}
+          PR: ${{ github.event.pull_request.number }}
         run: |
-          gh pr view "${{ github.event.pull_request.number }}" \
-            --repo "${{ github.repository }}" \
-            --json files --jq '.files[].path' > changed.txt
+          # the REST files endpoint (unlike `gh pr view --json files`) carries
+          # previous_filename on renames — required so a rename that lands a
+          # core path under a new name still classifies as core.
+          gh api "repos/$REPO/pulls/$PR/files" --paginate > files.json
+          PYTHONPATH=src python -m vouch.pr_bot changed-files --json-file files.json > changed.txt
       - name: fail if an untrusted author touched core
         env:
           ASSOC: ${{ github.event.pull_request.author_association }}

CHANGELOG.md

@@ -46,6 +46,13 @@ All notable changes to vouch are documented here. Format follows
   in config.yaml (#476).
 
 ### Fixed
+- `pr_bot` core-path classification: `trust-gate.yml`, `auto-merge.yml`,
+  and `comment-command.yml` now source the changed-file list from the REST
+  `pulls/{n}/files` endpoint instead of `gh pr view --json files`, and feed
+  both the new and previous filename into classification. the GraphQL-backed
+  shortcut carries no rename metadata, so a `git mv` of a `CORE_GLOBS` path
+  (e.g. `http_server.py`) made the file invisible to the trust gate and
+  auto-merge arm check. (#505)
 - approve/reject/expire record the audit event *before* moving the
   proposal to decided/. a crash between the two used to leave a durable
   decision with no authoritative history; it now leaves a pending

src/vouch/pr_bot.py

@@ -167,6 +167,26 @@ def _read_lines(path: str) -> list[str]:
         return [ln.strip() for ln in fh if ln.strip()]
 
 
+def extract_changed_paths(files_json: str) -> list[str]:
+    """flatten a REST ``/pulls/{n}/files`` payload into a path list.
+
+    emits both ``filename`` and, for a renamed entry, ``previous_filename`` —
+    a rename that lands a core path under a new name must still classify as
+    core. ``gh pr view --json files`` (the GraphQL-backed shortcut) carries no
+    previous-filename field and silently drops this; callers must use the
+    REST files endpoint (``gh api repos/{o}/{r}/pulls/{n}/files``) instead.
+    """
+    paths: list[str] = []
+    for entry in json.loads(files_json):
+        filename = entry.get("filename")
+        if filename:
+            paths.append(filename)
+        previous = entry.get("previous_filename")
+        if previous:
+            paths.append(previous)
+    return paths
+
+
 def main(argv: Sequence[str] | None = None) -> int:
     p = argparse.ArgumentParser(prog="vouch.pr_bot")
     sub = p.add_subparsers(dest="cmd", required=True)
@@ -175,6 +195,9 @@ def main(argv: Sequence[str] | None = None) -> int:
     c.add_argument("--files-file", required=True)
     c.add_argument("--print-klass", action="store_true")
 
+    cf = sub.add_parser("changed-files")
+    cf.add_argument("--json-file", required=True)
+
     for name in ("core-touched", "ui-touched"):
         sp = sub.add_parser(name)
         sp.add_argument("--files-file", required=True)
@@ -203,6 +226,11 @@ def main(argv: Sequence[str] | None = None) -> int:
         changed = _read_lines(ns.files_file)
         sys.stdout.write(klass(changed) if ns.print_klass else json.dumps(classify(changed)))
         return 0
+    if ns.cmd == "changed-files":
+        with open(ns.json_file, encoding="utf-8") as fh:
+            paths = extract_changed_paths(fh.read())
+        sys.stdout.write("\n".join(paths))
+        return 0
     if ns.cmd == "core-touched":
         return 0 if classify(_read_lines(ns.files_file))["is_core"] else 1
     if ns.cmd == "ui-touched":

tests/test_pr_bot.py

@@ -97,6 +97,47 @@ def test_cli_trust_exit_codes():
     assert ok.returncode == 0 and bad.returncode == 1
 
 
+def test_extract_changed_paths_plain_file():
+    files_json = '[{"filename": "src/vouch/context.py"}]'
+    assert pr_bot.extract_changed_paths(files_json) == ["src/vouch/context.py"]
+
+
+def test_extract_changed_paths_includes_previous_filename_on_rename():
+    files_json = (
+        '[{"filename": "src/vouch/web_server.py", "status": "renamed", '
+        '"previous_filename": "src/vouch/http_server.py"}]'
+    )
+    assert pr_bot.extract_changed_paths(files_json) == [
+        "src/vouch/web_server.py", "src/vouch/http_server.py",
+    ]
+
+
+def test_rename_of_core_path_still_classifies_core():
+    # a rename that lands a core path under a new name must not slip past
+    # trust-gate — the pre-rename path has to stay in the classified list.
+    files_json = (
+        '[{"filename": "src/vouch/web_server.py", "status": "renamed", '
+        '"previous_filename": "src/vouch/http_server.py"}]'
+    )
+    changed = pr_bot.extract_changed_paths(files_json)
+    assert pr_bot.classify(changed)["is_core"] is True
+
+
+def test_cli_changed_files_emits_previous_filename(tmp_path):
+    f = tmp_path / "files.json"
+    f.write_text(
+        '[{"filename": "src/vouch/web_server.py", "status": "renamed", '
+        '"previous_filename": "src/vouch/http_server.py"}]',
+        encoding="utf-8",
+    )
+    out = subprocess.run(
+        [sys.executable, "-m", "vouch.pr_bot", "changed-files", "--json-file", str(f)],
+        capture_output=True, text=True, check=True)
+    assert out.stdout.splitlines() == [
+        "src/vouch/web_server.py", "src/vouch/http_server.py",
+    ]
+
+
 def test_codeowners_covers_every_core_glob():
     text = Path(".github/CODEOWNERS").read_text(encoding="utf-8")
     for glob in pr_bot.CORE_GLOBS: