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Add a client extension API (#3034)

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Max 2026-06-30 21:31:02 +01:00 • committed by GitHub
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1 changed files with 3410 additions and 180 deletions
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20
tests/server/test_apps.py
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@ -14,6 +14,7 @@ import pytest
from inline_snapshot import snapshot
from mcp_types import CallToolResult, ReadResourceResult, TextContent, TextResourceContents
from mcp.client import advertise
from mcp.client.client import Client
from mcp.server import Server, ServerRequestContext
from mcp.server.apps import (
@ -95,7 +96,7 @@ async def test_apps_tool_returns_rich_output_when_client_negotiated_apps() -> No
branching on `client_supports_apps(ctx)`, drives both halves."""
server = _clock_server()
async with Client(server, extensions={EXTENSION_ID: {"mimeTypes": [APP_MIME_TYPE]}}) as supports:
async with Client(server, extensions=[advertise(EXTENSION_ID, {"mimeTypes": [APP_MIME_TYPE]})]) as supports:
rich = await supports.call_tool("get_time", {})
async with Client(server) as plain:
fallback = await plain.call_tool("get_time", {})
@ -104,7 +105,7 @@ async def test_apps_tool_returns_rich_output_when_client_negotiated_apps() -> No
assert fallback.content == snapshot([TextContent(text="The time is 2026-06-26T00:00:00Z.")])
async def _observed_client_supports_apps(extensions: dict[str, dict[str, Any]] | None) -> bool:
async def _observed_client_supports_apps(ui_settings: dict[str, Any] | None) -> bool:
"""Run one probe `tools/call` and report what `client_supports_apps` saw server-side.
Exercises the lowlevel `ServerRequestContext` form, which reads the client's
@ -123,29 +124,30 @@ async def _observed_client_supports_apps(extensions: dict[str, dict[str, Any]] |
return CallToolResult(content=[TextContent(text="ok")])
server = Server("probe", on_list_tools=list_tools, on_call_tool=call_tool)
extensions = None if ui_settings is None else [advertise(EXTENSION_ID, ui_settings)]
async with Client(server, extensions=extensions) as client:
await client.call_tool("probe", {})
return observed[0]
@pytest.mark.parametrize(
("extensions", "expected"),
("ui_settings", "expected"),
[
pytest.param({EXTENSION_ID: {"mimeTypes": [APP_MIME_TYPE]}}, True, id="html-mime-listed"),
pytest.param({EXTENSION_ID: {"mimeTypes": (APP_MIME_TYPE,)}}, True, id="in-process-tuple-mime-types"),
pytest.param({"mimeTypes": [APP_MIME_TYPE]}, True, id="html-mime-listed"),
pytest.param({"mimeTypes": (APP_MIME_TYPE,)}, True, id="in-process-tuple-mime-types"),
pytest.param(None, False, id="extension-not-declared"),
pytest.param({EXTENSION_ID: {"mimeTypes": ["application/x-other"]}}, False, id="html-mime-not-offered"),
pytest.param({EXTENSION_ID: {}}, False, id="mime-types-key-missing"),
pytest.param({"mimeTypes": ["application/x-other"]}, False, id="html-mime-not-offered"),
pytest.param({}, False, id="mime-types-key-missing"),
],
)
async def test_client_supports_apps_from_lowlevel_request_context(
extensions: dict[str, dict[str, Any]] | None, expected: bool
ui_settings: dict[str, Any] | None, expected: bool
) -> None:
"""ext-apps: `client_supports_apps` is `True` only when the client declared the ui
extension AND listed `text/html;profile=mcp-app` in its `mimeTypes` settings — a
required field, so its absence means unsupported (the reference SDK's check is
`uiCap?.mimeTypes?.includes(...)`)."""
assert await _observed_client_supports_apps(extensions) is expected
assert await _observed_client_supports_apps(ui_settings) is expected
def test_apps_tool_rejects_non_ui_resource_uri() -> None: