Fix function coverage checker def-line false positives

test/tools/check_function_coverage.py

@@ -21,6 +21,7 @@ class FunctionSpan:
     path: Path
     qualname: str
     lineno: int
+    body_lineno: int
     end_lineno: int
 
 
@@ -44,11 +45,13 @@ class FunctionCollector(ast.NodeVisitor):
     def _record(self, node: ast.FunctionDef | ast.AsyncFunctionDef) -> None:
         qualname = ".".join([*self.stack, node.name]) if self.stack else node.name
         end_lineno = getattr(node, "end_lineno", node.lineno)
+        body_lineno = getattr(node.body[0], "lineno", node.lineno) if node.body else node.lineno
         self.functions.append(
             FunctionSpan(
                 path=self.path,
                 qualname=qualname,
                 lineno=node.lineno,
+                body_lineno=body_lineno,
                 end_lineno=end_lineno,
             )
         )
@@ -92,7 +95,10 @@ def check_function_coverage(coverage_json: Path, *, report_only: bool = False) -
 
     for function in iter_package_functions():
         executed_lines = executed_by_path.get(function.path, set())
-        if not any(line in executed_lines for line in range(function.lineno, function.end_lineno + 1)):
+        if not any(
+            line in executed_lines
+            for line in range(function.body_lineno, function.end_lineno + 1)
+        ):
             missing.append(function)
 
     if not missing:

test/unit/test_check_function_coverage.py

@@ -0,0 +1,114 @@
+import importlib.util
+import json
+import sys
+from pathlib import Path
+
+
+def _load_checker_module():
+    module_path = (
+        Path(__file__).resolve().parents[1] / "tools" / "check_function_coverage.py"
+    )
+    spec = importlib.util.spec_from_file_location("check_function_coverage", module_path)
+    module = importlib.util.module_from_spec(spec)
+    assert spec.loader is not None
+    sys.modules[spec.name] = module
+    spec.loader.exec_module(module)
+    return module
+
+
+def test_function_collector_tracks_first_body_line_for_decorated_functions(tmp_path):
+    checker = _load_checker_module()
+    source = "\n".join(
+        [
+            "@decorator",
+            "def foo():",
+            "    '''doc'''",
+            "    return 1",
+            "",
+        ]
+    )
+    tree = checker.ast.parse(source)
+    collector = checker.FunctionCollector(Path("alphapulldown/example.py"))
+
+    collector.visit(tree)
+
+    function = collector.functions[0]
+    assert function.lineno == 2
+    assert function.body_lineno == 3
+    assert function.end_lineno == 4
+
+
+def test_check_function_coverage_ignores_definition_only_execution(
+    tmp_path,
+    monkeypatch,
+    capsys,
+):
+    checker = _load_checker_module()
+    coverage_json = tmp_path / "coverage.json"
+    coverage_json.write_text(
+        json.dumps(
+            {
+                "files": {
+                    "alphapulldown/example.py": {
+                        "executed_lines": [10],
+                    }
+                }
+            }
+        ),
+        encoding="utf-8",
+    )
+    monkeypatch.setattr(
+        checker,
+        "iter_package_functions",
+        lambda: [
+            checker.FunctionSpan(
+                path=Path("alphapulldown/example.py"),
+                qualname="foo",
+                lineno=10,
+                body_lineno=11,
+                end_lineno=12,
+            )
+        ],
+    )
+
+    exit_code = checker.check_function_coverage(coverage_json)
+
+    captured = capsys.readouterr()
+    assert exit_code == 1
+    assert "alphapulldown/example.py:10 foo" in captured.out
+
+
+def test_check_function_coverage_accepts_executed_function_body(tmp_path, monkeypatch, capsys):
+    checker = _load_checker_module()
+    coverage_json = tmp_path / "coverage.json"
+    coverage_json.write_text(
+        json.dumps(
+            {
+                "files": {
+                    "alphapulldown/example.py": {
+                        "executed_lines": [11],
+                    }
+                }
+            }
+        ),
+        encoding="utf-8",
+    )
+    monkeypatch.setattr(
+        checker,
+        "iter_package_functions",
+        lambda: [
+            checker.FunctionSpan(
+                path=Path("alphapulldown/example.py"),
+                qualname="foo",
+                lineno=10,
+                body_lineno=11,
+                end_lineno=12,
+            )
+        ],
+    )
+
+    exit_code = checker.check_function_coverage(coverage_json)
+
+    captured = capsys.readouterr()
+    assert exit_code == 0
+    assert "Function coverage check passed" in captured.out