FabledGrimoire/tests/test_mcp_strict_args.py

"""Unknown tool arguments are rejected, never silently dropped.

The failure this pins: MCPServer validates tool arguments with a pydantic model
whose extra-field policy is "ignore", so `create_note(content=...)` — a
plausible near-miss for `body=`, primed by add_task_log's `content` — would
run, store `body: ""`, and leave a record embedding/search cannot see, while
REPORTING SUCCESS.

The rejection is at the dispatch seam, not per-tool: StrictArgsMCPServer rejects any
call carrying arguments the tool does not declare, with a did-you-mean when
one is close. An error the caller sees once beats data half-written forever.
"""
import pytest
from mcp.server.mcpserver.exceptions import ToolError, UnexpectedToolError

from grimoire.mcp.server import StrictArgsMCPServer


def _echo_server() -> StrictArgsMCPServer:
    mcp = StrictArgsMCPServer("strict-test")

    @mcp.tool()
    def echo(text: str = "") -> str:
        return text

    return mcp


async def test_declared_arguments_still_dispatch():
    mcp = _echo_server()
    result = await mcp.call_tool("echo", {"text": "hi"})
    assert "hi" in str(result)


async def test_unknown_argument_is_an_error_not_a_silent_drop():
    """The load-bearing property: the call must FAIL, because succeeding is
    what turned a typo into data loss."""
    mcp = _echo_server()
    with pytest.raises(ToolError) as exc:
        await mcp.call_tool("echo", {"txt": "hi"})
    msg = str(exc.value)
    assert "'txt'" in msg
    assert "did you mean 'text'?" in msg          # difflib near-miss hint
    assert "Nothing was created or changed" in msg


async def test_empty_arguments_pass():
    mcp = _echo_server()
    assert await mcp.call_tool("echo", {}) is not None


async def test_unknown_tool_keeps_the_upstream_error():
    """The gate must not swallow or reshape 'no such tool' — that error path
    belongs to MCPServer and clients already understand it."""
    mcp = _echo_server()
    with pytest.raises(Exception) as exc:
        await mcp.call_tool("no_such_tool", {"text": "hi"})
    assert "no_such_tool" in str(exc.value)


# --- a refusal's text reaches the agent ---------------------------------------
#
# SDK 2.x passes on only a ToolError's text; anything else is wrapped as
# "Error executing tool X" and its message is kept on the server. ValueError is
# how every Grimoire tool refuses, so without this every refusal arrives bare.


def _raising_server() -> StrictArgsMCPServer:
    mcp = StrictArgsMCPServer("refusal-test")

    @mcp.tool()
    def refuse() -> str:
        raise ValueError("record 7 is not yours to change — open your own copy")

    @mcp.tool()
    def crash() -> str:
        raise RuntimeError("password=hunter2 at db.internal:5432")

    return mcp


async def test_a_refusal_reaches_the_caller_with_its_reason():
    mcp = _raising_server()
    with pytest.raises(ToolError) as exc:
        await mcp.call_tool("refuse", {})
    msg = str(exc.value)
    assert "Error executing tool refuse" in msg
    assert "record 7 is not yours to change — open your own copy" in msg
    assert not isinstance(exc.value, UnexpectedToolError), (
        "still typed as a crash, so the SDK's handler would log it as one")


async def test_a_crash_stays_masked():
    """Only the refusal convention is unmasked: a crash's text can carry
    internals, and the SDK hides it for that reason."""
    mcp = _raising_server()
    with pytest.raises(UnexpectedToolError) as exc:
        await mcp.call_tool("crash", {})
    assert "hunter2" not in str(exc.value)


@pytest.mark.usefixtures("_bind_user")
async def test_a_real_tools_refusal_reaches_the_caller():
    """Against the real server, on a refusal that needs no database: the
    message judge_menu writes for an empty verdict list."""
    from grimoire.mcp.server import build_mcp_server

    with pytest.raises(ToolError) as exc:
        await build_mcp_server().call_tool("judge_menu", {"log_id": 1, "verdicts": []})
    assert "at least one verdict" in str(exc.value)


async def test_the_real_server_refuses_content_on_create_note():
    """Against the REAL server: `content=` on create_note
    must raise before dispatch — naming the bad argument and listing `body`
    among the accepted ones — instead of creating a body-less note."""
    from grimoire.mcp.server import build_mcp_server

    mcp = build_mcp_server()
    assert isinstance(mcp, StrictArgsMCPServer)   # the guard is actually mounted
    with pytest.raises(ToolError) as exc:
        await mcp.call_tool(
            "create_note", {"title": "t", "content": "the body text"}
        )
    msg = str(exc.value)
    assert "'content'" in msg
    assert "body" in msg