aver: handle ] followed by trailing comment in module-effects strip

aallan · claude · aallan · commit 918c3e3694af · 2026-04-29T10:24:22.000+01:00
Both `stripped.endswith("]")` checks in _strip_module_effects were
brittle to Aver's trailing line comments (`// ...`). For an LLM-emitted
declaration like:

    effects [Console.print] // pure module

the strip pass would:
  1. match the opener regex (correctly)
  2. fail `endswith("]")` because the line ends in `e` (`pure`)
  3. enter `skip_until_close` mode
  4. chew through subsequent lines until something happens to end
     in `]` — likely catastrophic for the function body

Same hazard on the closing line of a multi-line list:

    effects [
        Console.print,
    ] // pure module

Replace both `endswith("]")` checks with `"]" in stripped`. Module-level
effect lists are simple identifier sequences with no string literals or
nested brackets, so the theoretical false-match concern (a `]` inside a
string in the list) doesn't apply now or in any planned Aver evolution.

Tests:
- `test_strips_inline_effects_with_trailing_comment` — the inline
  variant; asserts the function body is intact (i.e. NOT eaten by a
  runaway skip_until_close).
- `test_strips_multiline_effects_with_trailing_comment_on_close` — same
  hazard on the closing line of a multi-line list.

Both new tests pass; full `tests/test_runner.py` suite green
(106 passed locally).

Co-Authored-By: Claude Opus 4.6 &lt;noreply@anthropic.com&gt;
diff --git a/tests/test_runner.py b/tests/test_runner.py
@@ -986,6 +986,50 @@ def test_only_strips_inside_module_header(self):
         # Header `effects` line gone, fn-body `effects` line kept.
         assert sum(1 for line in lines if "effects [Console.print]" in line) == 1
 
+    def test_strips_inline_effects_with_trailing_comment(self):
+        # Aver allows `// ...` line comments; an inline `effects
+        # [...] // comment` declaration must be detected as
+        # single-line, not fall into the multi-line skip path that
+        # would chew through the function body.
+        code = (
+            "module M\n"
+            '    intent = "t"\n'
+            "    effects [Console.print] // pure module\n"
+            "\n"
+            "fn f() -> Unit\n"
+            "    ! [Console.print]\n"
+            '    Console.print("hi")\n'
+        )
+        result = _strip_module_effects(code)
+        # Header `effects` line is gone.
+        assert "effects [Console.print]" not in result
+        # And critically: the function body is intact, NOT eaten by
+        # a runaway skip_until_close.
+        assert "fn f() -> Unit" in result
+        assert 'Console.print("hi")' in result
+
+    def test_strips_multiline_effects_with_trailing_comment_on_close(self):
+        # Same hazard on the closing line of a multi-line list:
+        # `]` can be followed by a trailing comment.
+        code = (
+            "module M\n"
+            '    intent = "t"\n'
+            "    effects [\n"
+            "        Console.print,\n"
+            "    ] // pure module\n"
+            "\n"
+            "fn f() -> Unit\n"
+            "    ! [Console.print]\n"
+            '    Console.print("hi")\n'
+        )
+        result = _strip_module_effects(code)
+        # Whole effects block gone (header through close).
+        assert "effects [" not in result
+        assert "Console.print," not in result
+        # Function body intact.
+        assert "fn f() -> Unit" in result
+        assert 'Console.print("hi")' in result
+
 
 class TestEvaluateAverCode:
     def _sample_problem(self, test_cases=None):
diff --git a/vera_bench/runner.py b/vera_bench/runner.py
@@ -596,8 +596,11 @@ def _strip_module_effects(code: str) -> str:
 
         if skip_until_close:
             # Multi-line `effects [\n  ...\n]` — drop everything up to
-            # and including the line that closes the bracket.
-            if stripped.endswith("]"):
+            # and including the line that closes the bracket. Use
+            # presence rather than `endswith("]")` so a trailing line
+            # comment (Aver's `// ...` syntax) doesn't make us miss
+            # the close and chew through the rest of the file.
+            if "]" in stripped:
                 skip_until_close = False
             continue
 
@@ -622,7 +625,11 @@ def _strip_module_effects(code: str) -> str:
             and indent_len > 0
             and _AVER_EFFECTS_OPEN_RE.match(stripped)
         ):
-            if stripped.endswith("]"):
+            # Same `]`-presence rule as the skip_until_close branch —
+            # tolerates `effects [...] // pure module` (single-line
+            # declaration with a trailing comment) without falling into
+            # the multi-line skip path that would eat the function body.
+            if "]" in stripped:
                 continue
             skip_until_close = True
             continue
