fix(event_handler): support finding type annotated resolver when merging schemas (#8074)

* Support finding type annotated resolver

* Fix tests

---------

Co-authored-by: Leandro Damascena <lcdama@amazon.pt>

Author: siwyd

aws_lambda_powertools/event_handler/openapi/merge.py

@@ -67,11 +67,18 @@ def _file_has_resolver(file_path: Path, resolver_name: str) -> bool:
         return False
 
     for node in ast.walk(tree):
+        targets: list[ast.expr] = []
+        value: ast.expr | None = None
         if isinstance(node, ast.Assign):
-            for target in node.targets:
-                if isinstance(target, ast.Name) and target.id == resolver_name:
-                    if _is_resolver_call(node.value):
-                        return True
+            targets = node.targets
+            value = node.value
+        elif isinstance(node, ast.AnnAssign):
+            targets = [node.target]
+            value = node.value
+        for target in targets:
+            if isinstance(target, ast.Name) and target.id == resolver_name:
+                if value is not None and _is_resolver_call(value):
+                    return True
     return False
 
 

tests/functional/event_handler/_pydantic/merge_handlers/typed_handler.py

@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+from pydantic import BaseModel
+
+from aws_lambda_powertools.event_handler import APIGatewayRestResolver
+
+app: APIGatewayRestResolver = APIGatewayRestResolver(enable_validation=True)
+
+
+class Product(BaseModel):
+    id: int
+    name: str
+    price: float
+
+
+@app.get("/products")
+def get_products() -> list[Product]:
+    return [
+        Product(id=1, name="Widget", price=9.99),
+    ]
+
+
+def handler(event, context):
+    return app.resolve(event, context)

tests/functional/event_handler/_pydantic/test_openapi_merge.py

@@ -367,3 +367,19 @@ def test_openapi_merge_schema_is_cached():
 
     # AND paths should not be duplicated
     assert len([p for p in schema1["paths"] if p == "/users"]) == 1
+
+
+def test_openapi_merge_discover_type_annotated_resolver():
+    # GIVEN an OpenAPIMerge instance
+    merge = OpenAPIMerge(title="Typed API", version="1.0.0")
+
+    # WHEN discovering a handler with a type-annotated resolver (app: Resolver = Resolver())
+    merge.discover(
+        path=MERGE_HANDLERS_PATH,
+        pattern="**/typed_handler.py",
+        resolver_name="app",
+    )
+
+    # THEN it should find the resolver and include its routes in the schema
+    schema = merge.get_openapi_schema()
+    assert "/products" in schema["paths"]