codex: restore c golden update mode

docs/c_parser/c_parser_implementation_checklist.md

@@ -408,7 +408,8 @@ Scope:
       inputs.
 - [x] Regenerate all fixtures with the standalone golden script.
 - [x] Regenerate selected fixtures with the standalone golden script.
-- [x] Keep golden regeneration out of the comparison tests.
+- [x] Regenerate full C golden suites from comparison tests when
+      `C_PARSER_UPDATE_GOLDENS=1` is set.
 - [x] Create a C error golden generator.
 - [x] Store expected error type, message fragments, diagnostic fragments, and
       parser entrypoint metadata.

docs/c_parser/c_parser_reference.md

@@ -481,10 +481,10 @@ resolution. The `json` regression inputs
 intentionally retain recoverable diagnostics from unsupported constructs; they
 do not claim complete library parsing. Remaining parser-suite skips cover the
 pinned/provenanced corpus target and compiler-preprocessed `.i`/`#line`
-behavior; golden inventory checks also skip deliberately while update mode is
-rewriting their baselines. Future implementation branches should activate only
-the tests for the capability they implement, then merge those branches back
-into `c-parser/main`.
+behavior. Golden comparison tests rewrite their baselines when
+`C_PARSER_UPDATE_GOLDENS=1` is set. Future implementation branches should
+activate only the tests for the capability they implement, then merge those
+branches back into `c-parser/main`.
 
 ### Declaration Coverage Boundary
 
@@ -567,15 +567,12 @@ headers, such as `nanosvg.h` before `nanosvgrast.h`; an input without a
 sibling is parsed as a one-file project. Golden filenames use the project
 stem, such as `api.json` or `jsmn.json`. Goldens can be regenerated for all
 active projects with
-`python -m tests.parser.c.generate_c_parser_goldens` or for selected paths
-relative to `tests/data/c/` by adding either member filename; any matching
-sibling is included automatically. Fatal diagnostic goldens are regenerated
-with
-`python -m tests.parser.c.errors.generate_c_parser_error_goldens`.
-The parser goldens are regenerated by the standalone scripts above, not by
-the comparison tests. Until include-expanded parsing is implemented, a paired
-project records the source-to-header include edge but parses the `.c` and
-`.h` members separately.
+`C_PARSER_UPDATE_GOLDENS=1 PYTHONPATH=. pytest -q tests/parser/c/test_c_fixture_suite.py`.
+Fatal diagnostic goldens are regenerated with
+`C_PARSER_UPDATE_GOLDENS=1 PYTHONPATH=. pytest -q tests/parser/c/test_c_error_fixture_suite.py`.
+The standalone generator modules remain available for targeted refreshes.
+Until include-expanded parsing is implemented, a paired project records the
+source-to-header include edge but parses the `.c` and `.h` members separately.
 
 STB is treated as a family of independent single-file libraries: each
 top-level `.h` or `.c` input generates its own one-file project golden rather

tests/parser/c/README.md

@@ -49,7 +49,7 @@ produces `nanosvg.json`; STB produces one golden per top-level library input.
 Regenerate all parser goldens with:
 
 ```bash
-python -m tests.parser.c.generate_c_parser_goldens
+C_PARSER_UPDATE_GOLDENS=1 PYTHONPATH=. pytest -q tests/parser/c/test_c_fixture_suite.py
 ```
 
 Regenerate selected projects by naming either input relative to
@@ -65,9 +65,9 @@ Fatal diagnostic fixtures live in `tests/data/c/errors/parser/` and their
 expected metadata lives in `fixtures/errors/`. Regenerate them with:
 
 ```bash
-python -m tests.parser.c.errors.generate_c_parser_error_goldens
+C_PARSER_UPDATE_GOLDENS=1 PYTHONPATH=. pytest -q tests/parser/c/test_c_error_fixture_suite.py
 ```
 
-The comparison tests are read-only. Regenerate the expected files with the
-standalone generator, then rerun the tests to compare against the checked-in
-baselines.
+The standalone generator modules remain available for targeted refreshes, but
+the comparison tests also rewrite their checked-in baselines when
+`C_PARSER_UPDATE_GOLDENS=1` is set.

tests/parser/c/test_c_error_fixture_suite.py

@@ -2,6 +2,7 @@
 """C parser error fixture and diagnostic golden regression tests."""
 
 import json
+import os
 from pathlib import Path
 
 import pytest
@@ -21,6 +22,25 @@ def _load_expected_error(expected_path: Path) -> dict:
     return json.loads(expected_path.read_text(encoding="utf-8"))
 
 
+def _dump_expected_error(path: Path, error_type: str, exc, parser: str) -> None:
+    payload = {
+        "parser": parser,
+        "error_type": error_type,
+        "message_contains": [exc.base_message],
+        "diagnostic_contains": [
+            f"error[{exc.code}]",
+            exc.base_message,
+            exc.source_line.strip() if exc.source_line else "",
+        ],
+    }
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_text(json.dumps(payload, indent=2) + "\n", encoding="utf-8")
+
+
+def _update_mode_enabled() -> bool:
+    return os.getenv("C_PARSER_UPDATE_GOLDENS", "0") == "1"
+
+
 def test_c_error_fixture_suite_has_fixtures():
     fixtures = [path for path in _ERRORS_DIR.glob("*") if path.suffix.lower() in _SOURCE_SUFFIXES]
     assert fixtures, "No C parser error fixtures found in tests/data/c/errors/parser"
@@ -47,6 +67,16 @@ def test_c_error_fixture_suite_reports_expected_diagnostics():
         expected_path = _expected_path_for_fixture(fixture)
         source = fixture.read_text(encoding="utf-8")
 
+        if _update_mode_enabled():
+            try:
+                parse_c_file(source, filename=fixture.name)
+                raise AssertionError(
+                    f"Expected CParseError from {fixture.name} but no error was raised"
+                )
+            except CParseError as exc:
+                _dump_expected_error(expected_path, "CParseError", exc, "parse_c_file")
+            continue
+
         expected = _load_expected_error(expected_path)
         assert expected["parser"] == "parse_c_file"
         assert expected["error_type"] == "CParseError"

tests/parser/c/test_c_fixture_suite.py

@@ -2,6 +2,7 @@
 """C parser grouped-project fixture/golden regression tests."""
 
 import json
+import os
 from pathlib import Path
 
 import pytest
@@ -64,6 +65,15 @@ def _expected_path_for_project(data_subdir: str, project_key: Path) -> Path:
     return (_FIXTURES_DIR / data_subdir / project_key).with_suffix(".json")
 
 
+def _load_expected(expected_path: Path) -> dict:
+    return json.loads(expected_path.read_text(encoding="utf-8"))
+
+
+def _dump_expected(path: Path, parsed: dict) -> None:
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_text(json.dumps(parsed, indent=2) + "\n", encoding="utf-8")
+
+
 def _normalize_resolved_paths(value):
     if isinstance(value, dict):
         resolved_path = value.get("resolved_path")
@@ -101,6 +111,10 @@ def _serialize_project(fixtures: list[Path]) -> dict:
     return _normalize_resolved_paths(_parse_project(fixtures).to_dict())
 
 
+def _update_mode_enabled() -> bool:
+    return os.getenv("C_PARSER_UPDATE_GOLDENS", "0") == "1"
+
+
 @pytest.mark.parametrize("data_subdir", _FIXTURE_GROUPS)
 def test_c_fixture_golden_suite_has_inputs(data_subdir):
     fixtures = sorted((_DATA_DIR / data_subdir).glob("*"))
@@ -125,7 +139,11 @@ def test_c_fixture_golden_suite_compares_project_json(data_subdir):
         expected_path = _expected_path_for_project(data_subdir, project_key)
         parsed = _serialize_project(fixtures)
 
-        expected = json.loads(expected_path.read_text(encoding="utf-8"))
+        if _update_mode_enabled():
+            _dump_expected(expected_path, parsed)
+            continue
+
+        expected = _load_expected(expected_path)
         assert parsed == expected