Exclude module-level __getattr__/__dir__ functions from pyrefly coverage

pyrefly/lib/commands/coverage/collect.rs

@@ -740,11 +740,12 @@ fn parse_functions(
                     }
                 }
             } else {
-                // Keep only public, exported, non-deleted module-level functions.
+                // Keep only public, exported, non-deleted, non-excluded-dunder module-level functions.
                 if !exports.contains_key(&fun.def.name.id)
                     || (!is_public_name(fun.def.name.as_str())
                         && !dunder_all.contains(&fun.def.name.id))
                     || deleted.contains(&fun.def.name.id)
+                    || EXCLUDED_MODULE_DUNDERS.contains(&fun.def.name.as_str())
                 {
                     continue;
                 }
@@ -2554,6 +2555,13 @@ mod tests {
         compare_snapshot("private_in_all.expected.json", &report);
     }
 
+    /// PEP 562 module hooks written as `def` are excluded from the report (issue #4020).
+    #[test]
+    fn test_report_module_dunder_hooks() {
+        let report = build_module_report_for_test("module_dunder_hooks.py");
+        compare_snapshot("module_dunder_hooks.expected.json", &report);
+    }
+
     /// CPython-injected module globals are excluded even when control flow
     /// wraps them in Phi bindings (issue #3505).
     #[test]

pyrefly/lib/test/coverage/test_files/module_dunder_hooks.expected.json

@@ -0,0 +1,37 @@
+{
+  "name": "test",
+  "path": "test.py",
+  "names": [
+    "test.visible"
+  ],
+  "line_count": 20,
+  "symbol_reports": [
+    {
+      "kind": "function",
+      "name": "test.visible",
+      "n_typable": 1,
+      "n_typed": 1,
+      "n_any": 0,
+      "n_untyped": 0,
+      "location": {
+        "line": 18,
+        "column": 1
+      }
+    }
+  ],
+  "type_ignores": [],
+  "n_typable": 1,
+  "n_typed": 1,
+  "n_any": 0,
+  "n_untyped": 0,
+  "coverage": 100.0,
+  "strict_coverage": 100.0,
+  "n_functions": 1,
+  "n_methods": 0,
+  "n_function_params": 0,
+  "n_method_params": 0,
+  "n_classes": 0,
+  "n_attrs": 0,
+  "n_properties": 0,
+  "n_type_ignores": 0
+}

pyrefly/lib/test/coverage/test_files/module_dunder_hooks.py

@@ -0,0 +1,19 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+# Regression test for gh-4020: PEP 562 module hooks written as `def` must be
+# excluded from coverage, like the assignment form already is.
+
+
+def __getattr__(name):
+    return None
+
+
+def __dir__():
+    return []
+
+
+def visible() -> int:
+    return 1