feat: add paginated list decorators for prompts, resources, and tools (#1286)

Co-authored-by: Claude <noreply@anthropic.com>

tests/server/lowlevel/test_func_inspection.py

@@ -0,0 +1,292 @@
+"""Unit tests for func_inspection module.
+
+Tests the create_call_wrapper function which determines how to call handler functions
+with different parameter signatures and type hints.
+"""
+
+from typing import Any, Generic, TypeVar
+
+import pytest
+
+from mcp.server.lowlevel.func_inspection import create_call_wrapper
+from mcp.types import ListPromptsRequest, ListResourcesRequest, ListToolsRequest, PaginatedRequestParams
+
+T = TypeVar("T")
+
+
+@pytest.mark.anyio
+async def test_no_params_returns_deprecated_wrapper() -> None:
+    """Test: def foo() - should call without request."""
+    called_without_request = False
+
+    async def handler() -> list[str]:
+        nonlocal called_without_request
+        called_without_request = True
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should call handler without passing request
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    result = await wrapper(request)
+    assert called_without_request is True
+    assert result == ["test"]
+
+
+@pytest.mark.anyio
+async def test_param_with_default_returns_deprecated_wrapper() -> None:
+    """Test: def foo(thing: int = 1) - should call without request."""
+    called_without_request = False
+
+    async def handler(thing: int = 1) -> list[str]:
+        nonlocal called_without_request
+        called_without_request = True
+        return [f"test-{thing}"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should call handler without passing request (uses default value)
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    result = await wrapper(request)
+    assert called_without_request is True
+    assert result == ["test-1"]
+
+
+@pytest.mark.anyio
+async def test_typed_request_param_passes_request() -> None:
+    """Test: def foo(req: ListPromptsRequest) - should pass request through."""
+    received_request = None
+
+    async def handler(req: ListPromptsRequest) -> list[str]:
+        nonlocal received_request
+        received_request = req
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should pass request to handler
+    request = ListPromptsRequest(method="prompts/list", params=PaginatedRequestParams(cursor="test-cursor"))
+    await wrapper(request)
+
+    assert received_request is not None
+    assert received_request is request
+    params = getattr(received_request, "params", None)
+    assert params is not None
+    assert params.cursor == "test-cursor"
+
+
+@pytest.mark.anyio
+async def test_typed_request_with_default_param_passes_request() -> None:
+    """Test: def foo(req: ListPromptsRequest, thing: int = 1) - should pass request through."""
+    received_request = None
+    received_thing = None
+
+    async def handler(req: ListPromptsRequest, thing: int = 1) -> list[str]:
+        nonlocal received_request, received_thing
+        received_request = req
+        received_thing = thing
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should pass request to handler
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    await wrapper(request)
+
+    assert received_request is request
+    assert received_thing == 1  # default value
+
+
+@pytest.mark.anyio
+async def test_optional_typed_request_with_default_none_is_deprecated() -> None:
+    """Test: def foo(thing: int = 1, req: ListPromptsRequest | None = None) - old style."""
+    called_without_request = False
+
+    async def handler(thing: int = 1, req: ListPromptsRequest | None = None) -> list[str]:
+        nonlocal called_without_request
+        called_without_request = True
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should call handler without passing request
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    result = await wrapper(request)
+    assert called_without_request is True
+    assert result == ["test"]
+
+
+@pytest.mark.anyio
+async def test_untyped_request_param_is_deprecated() -> None:
+    """Test: def foo(req) - should call without request."""
+    called = False
+
+    async def handler(req):  # type: ignore[no-untyped-def]  # pyright: ignore[reportMissingParameterType]
+        nonlocal called
+        called = True
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)  # pyright: ignore[reportUnknownArgumentType]
+
+    # Wrapper should call handler without passing request, which will fail because req is required
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    # This will raise TypeError because handler expects 'req' but wrapper doesn't provide it
+    with pytest.raises(TypeError, match="missing 1 required positional argument"):
+        await wrapper(request)
+
+
+@pytest.mark.anyio
+async def test_any_typed_request_param_is_deprecated() -> None:
+    """Test: def foo(req: Any) - should call without request."""
+
+    async def handler(req: Any) -> list[str]:
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should call handler without passing request, which will fail because req is required
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    # This will raise TypeError because handler expects 'req' but wrapper doesn't provide it
+    with pytest.raises(TypeError, match="missing 1 required positional argument"):
+        await wrapper(request)
+
+
+@pytest.mark.anyio
+async def test_generic_typed_request_param_is_deprecated() -> None:
+    """Test: def foo(req: Generic[T]) - should call without request."""
+
+    async def handler(req: Generic[T]) -> list[str]:  # pyright: ignore[reportGeneralTypeIssues]
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should call handler without passing request, which will fail because req is required
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    # This will raise TypeError because handler expects 'req' but wrapper doesn't provide it
+    with pytest.raises(TypeError, match="missing 1 required positional argument"):
+        await wrapper(request)
+
+
+@pytest.mark.anyio
+async def test_wrong_typed_request_param_is_deprecated() -> None:
+    """Test: def foo(req: str) - should call without request."""
+
+    async def handler(req: str) -> list[str]:
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should call handler without passing request, which will fail because req is required
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    # This will raise TypeError because handler expects 'req' but wrapper doesn't provide it
+    with pytest.raises(TypeError, match="missing 1 required positional argument"):
+        await wrapper(request)
+
+
+@pytest.mark.anyio
+async def test_required_param_before_typed_request_attempts_to_pass() -> None:
+    """Test: def foo(thing: int, req: ListPromptsRequest) - attempts to pass request (will fail at runtime)."""
+    received_request = None
+
+    async def handler(thing: int, req: ListPromptsRequest) -> list[str]:
+        nonlocal received_request
+        received_request = req
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper will attempt to pass request, but it will fail at runtime
+    # because 'thing' is required and has no default
+    request = ListPromptsRequest(method="prompts/list", params=None)
+
+    # This will raise TypeError because 'thing' is missing
+    with pytest.raises(TypeError, match="missing 1 required positional argument: 'thing'"):
+        await wrapper(request)
+
+
+@pytest.mark.anyio
+async def test_positional_only_param_with_correct_type() -> None:
+    """Test: def foo(req: ListPromptsRequest, /) - should pass request through."""
+    received_request = None
+
+    async def handler(req: ListPromptsRequest, /) -> list[str]:
+        nonlocal received_request
+        received_request = req
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should pass request to handler
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    await wrapper(request)
+
+    assert received_request is request
+
+
+@pytest.mark.anyio
+async def test_keyword_only_param_with_correct_type() -> None:
+    """Test: def foo(*, req: ListPromptsRequest) - should pass request through."""
+    received_request = None
+
+    async def handler(*, req: ListPromptsRequest) -> list[str]:
+        nonlocal received_request
+        received_request = req
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Wrapper should pass request to handler with keyword argument
+    request = ListPromptsRequest(method="prompts/list", params=None)
+    await wrapper(request)
+
+    assert received_request is request
+
+
+@pytest.mark.anyio
+async def test_different_request_types() -> None:
+    """Test that wrapper works with different request types."""
+    # Test with ListResourcesRequest
+    received_request = None
+
+    async def handler(req: ListResourcesRequest) -> list[str]:
+        nonlocal received_request
+        received_request = req
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListResourcesRequest)
+
+    request = ListResourcesRequest(method="resources/list", params=None)
+    await wrapper(request)
+
+    assert received_request is request
+
+    # Test with ListToolsRequest
+    received_request = None
+
+    async def handler2(req: ListToolsRequest) -> list[str]:
+        nonlocal received_request
+        received_request = req
+        return ["test"]
+
+    wrapper2 = create_call_wrapper(handler2, ListToolsRequest)
+
+    request2 = ListToolsRequest(method="tools/list", params=None)
+    await wrapper2(request2)
+
+    assert received_request is request2
+
+
+@pytest.mark.anyio
+async def test_mixed_params_with_typed_request() -> None:
+    """Test: def foo(a: str, req: ListPromptsRequest, b: int = 5) - attempts to pass request."""
+
+    async def handler(a: str, req: ListPromptsRequest, b: int = 5) -> list[str]:
+        return ["test"]
+
+    wrapper = create_call_wrapper(handler, ListPromptsRequest)
+
+    # Will fail at runtime due to missing 'a'
+    request = ListPromptsRequest(method="prompts/list", params=None)
+
+    with pytest.raises(TypeError, match="missing 1 required positional argument: 'a'"):
+        await wrapper(request)