Ensure quoted URIs work; fix proxy template issue

src/fastmcp/server/proxy.py

@@ -1,4 +1,5 @@
 from typing import Any, cast
+from urllib.parse import quote
 
 import mcp.types
 from mcp.types import BlobResourceContents, TextResourceContents
@@ -104,8 +105,14 @@ class ProxyTemplate(ResourceTemplate):
         )
 
     async def create_resource(self, uri: str, params: dict[str, Any]) -> ProxyResource:
+        # dont use the provided uri, because it may not be the same as the
+        # uri_template on the remote server.
+        # quote params to ensure they are valid for the uri_template
+        parameterized_uri = self.uri_template.format(
+            **{k: quote(v, safe="") for k, v in params.items()}
+        )
         async with self._client:
-            result = await self._client.read_resource(uri)
+            result = await self._client.read_resource(parameterized_uri)
 
         if isinstance(result[0], TextResourceContents):
             value = result[0].text
@@ -116,7 +123,7 @@ class ProxyTemplate(ResourceTemplate):
 
         return ProxyResource(
             client=self._client,
-            uri=uri,
+            uri=parameterized_uri,
             name=self.name,
             description=self.description,
             mime_type=result[0].mimeType,

tests/resources/test_resource_template.py

@@ -374,3 +374,11 @@ class TestMatchUriTemplate:
         uri_template = "prefix+test://{x}/test/{y}"
         result = match_uri_template(uri=uri, uri_template=uri_template)
         assert result == expected_params
+
+    def test_quoted_params(self):
+        uri_template = "user://{name}/{email}"
+        quoted_name = quote("John Doe", safe="")
+        quoted_email = quote("john@example.com", safe="")
+        uri = f"user://{quoted_name}/{quoted_email}"
+        result = match_uri_template(uri=uri, uri_template=uri_template)
+        assert result == {"name": "John Doe", "email": "john@example.com"}

tests/server/test_mount.py

@@ -1,6 +1,7 @@
 import contextlib
+import json
+from urllib.parse import quote
 
-import pytest
 from mcp.types import TextContent
 
 from fastmcp.server.server import FastMCP
@@ -190,7 +191,6 @@ async def test_mount_multiple_prompts():
     assert "sql_explain_sql" in main_app._prompt_manager._prompts
 
 
-@pytest.mark.anyio
 async def test_mount_lifespan():
     """Test that the lifespan of a mounted app is properly handled."""
     # Create apps
@@ -346,3 +346,83 @@ async def test_mount_with_proxy_tools():
     result = await main_app.call_tool("api_get_data", {"query": "test"})
     assert isinstance(result[0], TextContent)
     assert result[0].text == "Data for query: test"
+
+
+async def test_mount_with_proxy_prompts():
+    """
+    Test mounting with prompts that have custom keys.
+
+    This tests that the prompt's name doesn't change even though the registered
+    key does, which is important for correct rendering.
+    """
+    # Create apps
+    main_app = FastMCP("MainApp")
+    api_app = FastMCP("APIApp")
+
+    @api_app.prompt()
+    def greeting(name: str) -> str:
+        return f"Hello, {name} from API!"
+
+    main_app.mount("api", await FastMCP.as_proxy(api_app))
+
+    result = await main_app.get_prompt("api_greeting", {"name": "World"})
+    assert len(result) > 0
+    assert isinstance(result[0].content, TextContent)
+    assert result[0].content.text == "Hello, World from API!"
+
+
+async def test_mount_with_proxy_resources():
+    """
+    Test mounting with resources that have custom keys.
+
+    This tests that the resource's name doesn't change even though the registered
+    key does, which is important for correct access.
+    """
+    # Create apps
+    main_app = FastMCP("MainApp")
+    api_app = FastMCP("APIApp")
+
+    # Create a resource in the API app
+    @api_app.resource(uri="config://settings")
+    def get_config():
+        return {
+            "api_key": "12345",
+            "base_url": "https://api.example.com",
+        }
+
+    main_app.mount("api", await FastMCP.as_proxy(api_app))
+
+    # Access the resource through the main app with the prefixed key
+    resource = await main_app.read_resource("api+config://settings")
+    assert resource is not None
+    resource = json.loads(resource)
+    assert resource["api_key"] == "12345"
+    assert resource["base_url"] == "https://api.example.com"
+
+
+async def test_mount_with_proxy_resource_templates():
+    """
+    Test mounting with resource templates that have custom keys.
+
+    This tests that the template's name doesn't change even though the registered
+    key does, which is important for correct instantiation.
+    """
+    # Create apps
+    main_app = FastMCP("MainApp")
+    api_app = FastMCP("APIApp")
+
+    # Create a resource template in the API app
+    @api_app.resource(uri="user://{name}/{email}")
+    def create_user(name: str, email: str):
+        return {"name": name, "email": email}
+
+    main_app.mount("api", await FastMCP.as_proxy(api_app))
+
+    # Instantiate the template through the main app with the prefixed key
+    quoted_name = quote("John Doe", safe="")
+    quoted_email = quote("john@example.com", safe="")
+    user = await main_app.read_resource(f"api+user://{quoted_name}/{quoted_email}")
+    assert user is not None
+    user = json.loads(user)
+    assert user["name"] == "John Doe"
+    assert user["email"] == "john@example.com"