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| 1 | +"""Compiled tool validators are built once per listing and reused (issue #3676). |
| 2 | +
|
| 3 | +One-shot `jsonschema.validate` re-selects the validator class, checks the |
| 4 | +schema against the meta-schema, and resolves `$ref`s on every `tools/call`. |
| 5 | +The server now compiles per-tool validators once and reuses them, mirroring |
| 6 | +the client-side fix from #3134. |
| 7 | +""" |
| 8 | + |
| 9 | +from collections.abc import Awaitable, Callable |
| 10 | +from typing import Any |
| 11 | + |
| 12 | +import pytest |
| 13 | + |
| 14 | +import mcp.server.lowlevel.server as lowlevel_server |
| 15 | +from mcp.server import Server |
| 16 | +from mcp.types import CallToolRequest, CallToolRequestParams, CallToolResult, ListToolsRequest, TextContent, Tool |
| 17 | + |
| 18 | + |
| 19 | +def make_tool(extra_required: bool = False) -> Tool: |
| 20 | + required = ["name"] + (["nickname"] if extra_required else []) |
| 21 | + return Tool( |
| 22 | + name="greet", |
| 23 | + description="Greet someone", |
| 24 | + inputSchema={ |
| 25 | + "type": "object", |
| 26 | + "properties": { |
| 27 | + "name": {"type": "string"}, |
| 28 | + "nickname": {"type": "string"}, |
| 29 | + }, |
| 30 | + "required": required, |
| 31 | + "additionalProperties": False, |
| 32 | + }, |
| 33 | + outputSchema={ |
| 34 | + "type": "object", |
| 35 | + "properties": {"greeting": {"type": "string"}}, |
| 36 | + "required": ["greeting"], |
| 37 | + "additionalProperties": False, |
| 38 | + }, |
| 39 | + ) |
| 40 | + |
| 41 | + |
| 42 | +def make_server( |
| 43 | + tools: Callable[[], list[Tool]], |
| 44 | + handler: Callable[[str, dict[str, Any]], Awaitable[Any]], |
| 45 | +) -> Server: |
| 46 | + server = Server("test") |
| 47 | + |
| 48 | + @server.list_tools() |
| 49 | + async def list_tools() -> list[Tool]: |
| 50 | + return tools() |
| 51 | + |
| 52 | + @server.call_tool() |
| 53 | + async def call_tool(name: str, arguments: dict[str, Any]) -> Any: |
| 54 | + return await handler(name, arguments) |
| 55 | + |
| 56 | + return server |
| 57 | + |
| 58 | + |
| 59 | +def call_request(name: str, arguments: dict[str, Any]) -> CallToolRequest: |
| 60 | + return CallToolRequest( |
| 61 | + method="tools/call", |
| 62 | + params=CallToolRequestParams(name=name, arguments=arguments), |
| 63 | + ) |
| 64 | + |
| 65 | + |
| 66 | +async def greet_handler(name: str, arguments: dict[str, Any]) -> dict[str, Any]: |
| 67 | + assert name == "greet" |
| 68 | + return {"greeting": f"Hello, {arguments['name']}!"} |
| 69 | + |
| 70 | + |
| 71 | +async def call(server: Server, arguments: dict[str, Any]) -> CallToolResult: |
| 72 | + handler = server.request_handlers[CallToolRequest] |
| 73 | + result = await handler(call_request("greet", arguments)) |
| 74 | + assert result is not None |
| 75 | + assert isinstance(result.root, CallToolResult) |
| 76 | + return result.root |
| 77 | + |
| 78 | + |
| 79 | +@pytest.mark.anyio |
| 80 | +async def test_validators_compiled_once_and_reused(monkeypatch: pytest.MonkeyPatch) -> None: |
| 81 | + """N calls compile exactly one input and one output validator.""" |
| 82 | + calls = 0 |
| 83 | + real_validator_for = lowlevel_server.validator_for |
| 84 | + |
| 85 | + def counting_validator_for(schema: Any, *args: Any, **kwargs: Any) -> Any: |
| 86 | + nonlocal calls |
| 87 | + calls += 1 |
| 88 | + return real_validator_for(schema, *args, **kwargs) |
| 89 | + |
| 90 | + monkeypatch.setattr(lowlevel_server, "validator_for", counting_validator_for) |
| 91 | + |
| 92 | + server = make_server(lambda: [make_tool()], greet_handler) |
| 93 | + for _ in range(3): |
| 94 | + res = await call(server, {"name": "Ada"}) |
| 95 | + assert not res.isError |
| 96 | + assert calls == 2 # one input-schema compile + one output-schema compile |
| 97 | + |
| 98 | + |
| 99 | +@pytest.mark.anyio |
| 100 | +async def test_invalid_input_message_preserved() -> None: |
| 101 | + """Same error contract as one-shot validation: isError + prefix.""" |
| 102 | + server = make_server(lambda: [make_tool()], greet_handler) |
| 103 | + res = await call(server, {}) |
| 104 | + assert res.isError |
| 105 | + first = res.content[0] |
| 106 | + assert isinstance(first, TextContent) |
| 107 | + assert first.text.startswith("Input validation error: ") |
| 108 | + assert "'name' is a required property" in first.text |
| 109 | + |
| 110 | + |
| 111 | +@pytest.mark.anyio |
| 112 | +async def test_invalid_output_message_preserved() -> None: |
| 113 | + """Structured output violating outputSchema keeps the error contract.""" |
| 114 | + |
| 115 | + async def bad_handler(name: str, arguments: dict[str, Any]) -> dict[str, Any]: |
| 116 | + return {"wrong": "shape"} |
| 117 | + |
| 118 | + server = make_server(lambda: [make_tool()], bad_handler) |
| 119 | + res = await call(server, {"name": "Ada"}) |
| 120 | + assert res.isError |
| 121 | + first = res.content[0] |
| 122 | + assert isinstance(first, TextContent) |
| 123 | + assert first.text.startswith("Output validation error: ") |
| 124 | + |
| 125 | + |
| 126 | +@pytest.mark.anyio |
| 127 | +async def test_relisted_schema_is_recompiled(monkeypatch: pytest.MonkeyPatch) -> None: |
| 128 | + """A re-listed tool object triggers exactly one recompile and new rules apply.""" |
| 129 | + calls = 0 |
| 130 | + real_validator_for = lowlevel_server.validator_for |
| 131 | + |
| 132 | + def counting_validator_for(schema: Any, *args: Any, **kwargs: Any) -> Any: |
| 133 | + nonlocal calls |
| 134 | + calls += 1 |
| 135 | + return real_validator_for(schema, *args, **kwargs) |
| 136 | + |
| 137 | + monkeypatch.setattr(lowlevel_server, "validator_for", counting_validator_for) |
| 138 | + |
| 139 | + current = {"tool": make_tool()} |
| 140 | + server = make_server(lambda: [current["tool"]], greet_handler) |
| 141 | + |
| 142 | + res = await call(server, {"name": "Ada"}) |
| 143 | + assert not res.isError |
| 144 | + assert calls == 2 |
| 145 | + |
| 146 | + # Re-list with a stricter schema: refreshed tool objects must recompile. |
| 147 | + # The failing call recompiles only the input validator (lazy output |
| 148 | + # compile is skipped on the error path). |
| 149 | + current["tool"] = make_tool(extra_required=True) |
| 150 | + await server.request_handlers[ListToolsRequest](None) |
| 151 | + res = await call(server, {"name": "Ada"}) |
| 152 | + assert res.isError |
| 153 | + first = res.content[0] |
| 154 | + assert isinstance(first, TextContent) |
| 155 | + assert "'nickname' is a required property" in first.text |
| 156 | + assert calls == 3 |
| 157 | + |
| 158 | + # A valid call under the new schema compiles the output validator too. |
| 159 | + res = await call(server, {"name": "Ada", "nickname": "A"}) |
| 160 | + assert not res.isError |
| 161 | + assert calls == 4 |
| 162 | + |
| 163 | + |
| 164 | +@pytest.mark.anyio |
| 165 | +async def test_validate_input_false_skips_input_compile(monkeypatch: pytest.MonkeyPatch) -> None: |
| 166 | + """validate_input=False keeps skipping input validation entirely.""" |
| 167 | + calls = 0 |
| 168 | + real_validator_for = lowlevel_server.validator_for |
| 169 | + |
| 170 | + def counting_validator_for(schema: Any, *args: Any, **kwargs: Any) -> Any: |
| 171 | + nonlocal calls |
| 172 | + calls += 1 |
| 173 | + return real_validator_for(schema, *args, **kwargs) |
| 174 | + |
| 175 | + monkeypatch.setattr(lowlevel_server, "validator_for", counting_validator_for) |
| 176 | + |
| 177 | + server = Server("test") |
| 178 | + |
| 179 | + @server.list_tools() |
| 180 | + async def list_tools() -> list[Tool]: |
| 181 | + return [make_tool()] |
| 182 | + |
| 183 | + @server.call_tool(validate_input=False) |
| 184 | + async def call_tool(name: str, arguments: dict[str, Any]) -> Any: |
| 185 | + assert name == "greet" |
| 186 | + return {"greeting": "Hello!"} |
| 187 | + |
| 188 | + # Invalid input passes through; only the output schema compiles. |
| 189 | + res = await call(server, {}) |
| 190 | + assert not res.isError |
| 191 | + assert calls == 1 |
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