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Ensure openapi resources return valid responses

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This commit is contained in:
Jeremiah Lowin 2025-04-25 12:22:30 -04:00
commit 63d8b1b723
2 changed files with 152 additions and 75 deletions
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35
src/fastmcp/server/openapi.py
View file

@ -257,7 +257,7 @@ class OpenAPIResource(Resource):
self._client = client
self._route = route
async def read(self) -> str:
async def read(self) -> str | bytes:
"""Fetch the resource data by making an HTTP request."""
try:
# Extract path parameters from the URI if present
@ -297,15 +297,15 @@ class OpenAPIResource(Resource):
# Raise for 4xx/5xx responses
response.raise_for_status()
# Return response content based on mime type
if self.mime_type == "application/json":
try:
return response.json()
except (json.JSONDecodeError, ValueError):
# Fallback to returning the text
return response.text
else:
# Determine content type and return appropriate format
content_type = response.headers.get("content-type", "").lower()
if "application/json" in content_type:
return str(response.json())
elif any(ct in content_type for ct in ["text/", "application/xml"]):
return response.text
else:
return response.content
except httpx.HTTPStatusError as e:
# Handle HTTP errors (4xx, 5xx)
@ -367,18 +367,15 @@ class OpenAPIResourceTemplate(ResourceTemplate):
# Raise for 4xx/5xx responses
response.raise_for_status()
# Determine the mime type from the response
content_type = response.headers.get("content-type", "application/json")
mime_type = content_type.split(";")[0].strip()
# Determine content type and return appropriate format
content_type = response.headers.get("content-type", "").lower()
# Return the appropriate data
if mime_type == "application/json":
try:
return response.json()
except (json.JSONDecodeError, ValueError):
return response.text
else:
if "application/json" in content_type:
return str(response.json())
elif any(ct in content_type for ct in ["text/", "application/xml"]):
return response.text
else:
return response.content
except httpx.HTTPStatusError as e:
error_message = (

192
tests/server/test_openapi.py
View file

@ -1,12 +1,13 @@
import base64
import json
import re
import httpx
import pytest
from dirty_equals import IsStr
from fastapi import FastAPI, HTTPException
from fastapi import FastAPI, HTTPException, Response
from httpx import ASGITransport, AsyncClient
from mcp.types import TextContent
from mcp.types import BlobResourceContents, TextContent, TextResourceContents
from pydantic import BaseModel, TypeAdapter
from pydantic.networks import AnyUrl
@ -66,6 +67,17 @@ def fastapi_app(users_db: dict[int, User]) -> FastAPI:
user.name = name
return user
@app.get("/ping")
async def ping() -> str:
"""Ping the server."""
return "pong"
@app.get("/ping-bytes")
async def ping_bytes() -> Response:
"""Ping the server and get a bytes response."""
return Response(content=b"pong")
return app
@ -120,7 +132,8 @@ class TestTools:
"""
By default, tools exclude GET methods
"""
tools = await fastmcp_openapi_server._mcp_list_tools()
async with Client(fastmcp_openapi_server) as client:
tools = await client.list_tools()
assert len(tools) == 2
assert tools[0].model_dump() == dict(
@ -156,9 +169,10 @@ class TestTools:
"""
The tool created by the OpenAPI server should be the same as the original
"""
tool_response = await fastmcp_openapi_server._mcp_call_tool(
"create_user_users_post", {"name": "David", "active": False}
)
async with Client(fastmcp_openapi_server) as client:
tool_response = await client.call_tool(
"create_user_users_post", {"name": "David", "active": False}
)
# Convert TextContent to dict for comparison
assert isinstance(tool_response, list) and len(tool_response) == 1
@ -173,10 +187,13 @@ class TestTools:
assert len(response.json()) == 4
# Check that the user was created via MCP
user_response = await fastmcp_openapi_server._mcp_read_resource(
"resource://openapi/get_user_users__user_id__get/4"
)
user = user_response[0].content
async with Client(fastmcp_openapi_server) as client:
user_response = await client.read_resource(
"resource://openapi/get_user_users__user_id__get/4"
)
assert isinstance(user_response[0], TextResourceContents)
response_text = user_response[0].text
user = json.loads(response_text)
assert user == expected_user
async def test_call_update_user_name_tool(
@ -185,9 +202,11 @@ class TestTools:
"""
The tool created by the OpenAPI server should be the same as the original
"""
tool_response = await fastmcp_openapi_server._mcp_call_tool(
"update_user_name_users__user_id__name_patch", {"user_id": 1, "name": "XYZ"}
)
async with Client(fastmcp_openapi_server) as client:
tool_response = await client.call_tool(
"update_user_name_users__user_id__name_patch",
{"user_id": 1, "name": "XYZ"},
)
# Convert TextContent to dict for comparison
assert isinstance(tool_response, list) and len(tool_response) == 1
@ -202,10 +221,13 @@ class TestTools:
assert expected_data in response.json()
# Check that the user was updated via MCP
user_response = await fastmcp_openapi_server._mcp_read_resource(
"resource://openapi/get_user_users__user_id__get/1"
)
user = user_response[0].content
async with Client(fastmcp_openapi_server) as client:
user_response = await client.read_resource(
"resource://openapi/get_user_users__user_id__get/1"
)
assert isinstance(user_response[0], TextResourceContents)
response_text = user_response[0].text
user = json.loads(response_text)
assert user == expected_data
@ -214,8 +236,9 @@ class TestResources:
"""
By default, resources exclude GET methods without parameters
"""
resources = await fastmcp_openapi_server._mcp_list_resources()
assert len(resources) == 1
async with Client(fastmcp_openapi_server) as client:
resources = await client.list_resources()
assert len(resources) == 3
assert resources[0].uri == AnyUrl("resource://openapi/get_users_users_get")
assert resources[0].name == "get_users_users_get"
@ -228,17 +251,47 @@ class TestResources:
"""
The resource created by the OpenAPI server should be the same as the original
"""
json_users = TypeAdapter(list[User]).dump_python(
sorted(users_db.values(), key=lambda x: x.id)
)
resource_response = await fastmcp_openapi_server._mcp_read_resource(
"resource://openapi/get_users_users_get"
)
resource = resource_response[0].content
async with Client(fastmcp_openapi_server) as client:
resource_response = await client.read_resource(
"resource://openapi/get_users_users_get"
)
assert isinstance(resource_response[0], TextResourceContents)
response_text = resource_response[0].text
resource = json.loads(response_text)
assert resource == json_users
response = await api_client.get("/users")
assert response.json() == json_users
async def test_get_bytes_resource(
self,
fastmcp_openapi_server: FastMCPOpenAPI,
api_client,
):
"""Test reading a resource that returns bytes."""
async with Client(fastmcp_openapi_server) as client:
resource_response = await client.read_resource(
"resource://openapi/ping_bytes_ping_bytes_get"
)
assert isinstance(resource_response[0], BlobResourceContents)
assert base64.b64decode(resource_response[0].blob) == b"pong"
async def test_get_str_resource(
self,
fastmcp_openapi_server: FastMCPOpenAPI,
api_client,
):
"""Test reading a resource that returns a string."""
async with Client(fastmcp_openapi_server) as client:
resource_response = await client.read_resource(
"resource://openapi/ping_ping_get"
)
assert isinstance(resource_response[0], TextResourceContents)
assert resource_response[0].text == "pong"
class TestResourceTemplates:
async def test_list_resource_templates(
@ -247,7 +300,8 @@ class TestResourceTemplates:
"""
By default, resource templates exclude GET methods without parameters
"""
resource_templates = await fastmcp_openapi_server._mcp_list_resource_templates()
async with Client(fastmcp_openapi_server) as client:
resource_templates = await client.list_resource_templates()
assert len(resource_templates) == 1
assert resource_templates[0].name == "get_user_users__user_id__get"
assert (
@ -265,11 +319,14 @@ class TestResourceTemplates:
The resource template created by the OpenAPI server should be the same as the original
"""
user_id = 2
resource_response = await fastmcp_openapi_server._mcp_read_resource(
f"resource://openapi/get_user_users__user_id__get/{user_id}"
)
async with Client(fastmcp_openapi_server) as client:
resource_response = await client.read_resource(
f"resource://openapi/get_user_users__user_id__get/{user_id}"
)
assert isinstance(resource_response[0], TextResourceContents)
response_text = resource_response[0].text
resource = json.loads(response_text)
resource = resource_response[0].content
assert resource == users_db[user_id].model_dump()
response = await api_client.get(f"/users/{user_id}")
assert resource == response.json()
@ -280,7 +337,8 @@ class TestPrompts:
"""
By default, there are no prompts.
"""
prompts = await fastmcp_openapi_server._mcp_list_prompts()
async with Client(fastmcp_openapi_server) as client:
prompts = await client.list_prompts()
assert len(prompts) == 0
@ -494,20 +552,23 @@ class TestOpenAPI30Compatibility:
async def test_resource_discovery(self, openapi_30_server):
"""Test that resources are correctly discovered from an OpenAPI 3.0 spec."""
resources = await openapi_30_server._mcp_list_resources()
async with Client(openapi_30_server) as client:
resources = await client.list_resources()
assert len(resources) == 1
assert resources[0].uri == AnyUrl("resource://openapi/listProducts")
async def test_resource_template_discovery(self, openapi_30_server):
"""Test that resource templates are correctly discovered from an OpenAPI 3.0 spec."""
templates = await openapi_30_server._mcp_list_resource_templates()
async with Client(openapi_30_server) as client:
templates = await client.list_resource_templates()
assert len(templates) == 1
assert templates[0].name == "getProduct"
assert templates[0].uriTemplate == r"resource://openapi/getProduct/{product_id}"
async def test_tool_discovery(self, openapi_30_server):
"""Test that tools are correctly discovered from an OpenAPI 3.0 spec."""
tools = await openapi_30_server._mcp_list_tools()
async with Client(openapi_30_server) as client:
tools = await client.list_tools()
assert len(tools) == 1
assert tools[0].name == "createProduct"
assert "name" in tools[0].inputSchema["properties"]
@ -515,20 +576,26 @@ class TestOpenAPI30Compatibility:
async def test_resource_access(self, openapi_30_server):
"""Test reading a resource from an OpenAPI 3.0 server."""
resource_response = await openapi_30_server._mcp_read_resource(
"resource://openapi/listProducts"
)
content = resource_response[0].content
async with Client(openapi_30_server) as client:
resource_response = await client.read_resource(
"resource://openapi/listProducts"
)
assert isinstance(resource_response[0], TextResourceContents)
response_text = resource_response[0].text
content = json.loads(response_text)
assert len(content) == 2
assert content[0]["name"] == "Product 1"
assert content[1]["name"] == "Product 2"
async def test_resource_template_access(self, openapi_30_server):
"""Test reading a resource from template from an OpenAPI 3.0 server."""
resource_response = await openapi_30_server._mcp_read_resource(
"resource://openapi/getProduct/p1"
)
content = resource_response[0].content
async with Client(openapi_30_server) as client:
resource_response = await client.read_resource(
"resource://openapi/getProduct/p1"
)
assert isinstance(resource_response[0], TextResourceContents)
response_text = resource_response[0].text
content = json.loads(response_text)
assert content["id"] == "p1"
assert content["name"] == "Product 1"
assert content["price"] == 19.99
@ -665,20 +732,23 @@ class TestOpenAPI31Compatibility:
async def test_resource_discovery(self, openapi_31_server):
"""Test that resources are correctly discovered from an OpenAPI 3.1 spec."""
resources = await openapi_31_server._mcp_list_resources()
async with Client(openapi_31_server) as client:
resources = await client.list_resources()
assert len(resources) == 1
assert resources[0].uri == AnyUrl("resource://openapi/listOrders")
async def test_resource_template_discovery(self, openapi_31_server):
"""Test that resource templates are correctly discovered from an OpenAPI 3.1 spec."""
templates = await openapi_31_server._mcp_list_resource_templates()
async with Client(openapi_31_server) as client:
templates = await client.list_resource_templates()
assert len(templates) == 1
assert templates[0].name == "getOrder"
assert templates[0].uriTemplate == r"resource://openapi/getOrder/{order_id}"
async def test_tool_discovery(self, openapi_31_server):
"""Test that tools are correctly discovered from an OpenAPI 3.1 spec."""
tools = await openapi_31_server._mcp_list_tools()
async with Client(openapi_31_server) as client:
tools = await client.list_tools()
assert len(tools) == 1
assert tools[0].name == "createOrder"
assert "customer" in tools[0].inputSchema["properties"]
@ -686,20 +756,26 @@ class TestOpenAPI31Compatibility:
async def test_resource_access(self, openapi_31_server):
"""Test reading a resource from an OpenAPI 3.1 server."""
resource_response = await openapi_31_server._mcp_read_resource(
"resource://openapi/listOrders"
)
content = resource_response[0].content
async with Client(openapi_31_server) as client:
resource_response = await client.read_resource(
"resource://openapi/listOrders"
)
assert isinstance(resource_response[0], TextResourceContents)
response_text = resource_response[0].text
content = json.loads(response_text)
assert len(content) == 2
assert content[0]["customer"] == "Alice"
assert content[1]["customer"] == "Bob"
async def test_resource_template_access(self, openapi_31_server):
"""Test reading a resource from template from an OpenAPI 3.1 server."""
resource_response = await openapi_31_server._mcp_read_resource(
"resource://openapi/getOrder/o1"
)
content = resource_response[0].content
async with Client(openapi_31_server) as client:
resource_response = await client.read_resource(
"resource://openapi/getOrder/o1"
)
assert isinstance(resource_response[0], TextResourceContents)
response_text = resource_response[0].text
content = json.loads(response_text)
assert content["id"] == "o1"
assert content["customer"] == "Alice"
assert content["items"] == ["item1", "item2"]
@ -729,8 +805,9 @@ class TestMountFastMCP:
await mcp.import_server("fastapi", fastmcp_openapi_server)
# Check that resources are available with prefixed URIs
resources = await mcp._mcp_list_resources()
assert len(resources) == 1
async with Client(mcp) as client:
resources = await client.list_resources()
assert len(resources) == 3
# We're checking the key used by mcp to store the resource
# The prefixed URI is used as the key, but the resource's original uri is preserved
prefixed_uri = "fastapi+resource://openapi/get_users_users_get"
@ -738,7 +815,8 @@ class TestMountFastMCP:
assert resource is not None
# Check that templates are available with prefixed URIs
templates = await mcp._mcp_list_resource_templates()
async with Client(mcp) as client:
templates = await client.list_resource_templates()
assert len(templates) == 1
assert templates[0].name == "get_user_users__user_id__get"
prefixed_template_uri = (
@ -748,10 +826,12 @@ class TestMountFastMCP:
assert template is not None
# Check that tools are available with prefixed names
tools = await mcp._mcp_list_tools()
async with Client(mcp) as client:
tools = await client.list_tools()
assert len(tools) == 2
assert tools[0].name == "fastapi_create_user_users_post"
assert tools[1].name == "fastapi_update_user_name_users__user_id__name_patch"
prompts = await mcp._mcp_list_prompts()
async with Client(mcp) as client:
prompts = await client.list_prompts()
assert len(prompts) == 0