Regenerate generated files automatically if any are changed

.pre-commit-config.yaml

@@ -4,6 +4,7 @@ ci:
   autoupdate_commit_msg: "[pre-commit.ci] pre-commit autoupdate"
   autoupdate_schedule: weekly
   submodules: false
+  skip: [regenerate-files]
 
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
@@ -33,3 +34,11 @@ repos:
     rev: v2.3.0
     hooks:
       - id: codespell
+  - repo: local
+    hooks:
+      - id: regenerate-files
+        name: regenerate generated files
+        language: system
+        entry: python src/trio/_tools/gen_exports.py
+        pass_filenames: false
+        files: ^src\/trio\/_core\/(_generated)?(_run|(_i(o_(common|epoll|kqueue|windows)|nstrumentation)))\.py$

src/trio/_tests/tools/test_gen_exports.py

@@ -91,7 +91,9 @@ def test_create_pass_through_args() -> None:
 
 @skip_lints
 @pytest.mark.parametrize("imports", [IMPORT_1, IMPORT_2, IMPORT_3])
-def test_process(tmp_path: Path, imports: str) -> None:
+def test_process(
+    tmp_path: Path, imports: str, capsys: pytest.CaptureFixture[str]
+) -> None:
     try:
         import black  # noqa: F401
     # there's no dedicated CI run that has astor+isort, but lacks black.
@@ -106,7 +108,13 @@ def test_process(tmp_path: Path, imports: str) -> None:
     with pytest.raises(SystemExit) as excinfo:
         process([file], do_test=True)
     assert excinfo.value.code == 1
-    process([file], do_test=False)
+    captured = capsys.readouterr()
+    assert "Generated sources are outdated. Please regenerate." in captured.out
+    with pytest.raises(SystemExit) as excinfo:
+        process([file], do_test=False)
+    assert excinfo.value.code == 1
+    captured = capsys.readouterr()
+    assert "Regenerated sources successfully." in captured.out
     assert genpath.exists()
     process([file], do_test=True)
     # But if we change the lookup path it notices

src/trio/_tools/gen_exports.py

@@ -289,8 +289,9 @@ def process(files: Iterable[File], *, do_test: bool) -> None:
         dirname, basename = os.path.split(file.path)
         new_path = os.path.join(dirname, PREFIX + basename)
         new_files[new_path] = new_source
+    matches_disk = matches_disk_files(new_files)
     if do_test:
-        if not matches_disk_files(new_files):
+        if not matches_disk:
             print("Generated sources are outdated. Please regenerate.")
             sys.exit(1)
         else:
@@ -300,6 +301,9 @@ def process(files: Iterable[File], *, do_test: bool) -> None:
             with open(new_path, "w", encoding="utf-8") as f:
                 f.write(new_source)
         print("Regenerated sources successfully.")
+        if not matches_disk:
+            # With pre-commit integration, show that we edited files.
+            sys.exit(1)
 
 
 # This is in fact run in CI, but only in the formatting check job, which