chore: import upstream snapshot with attribution

examples/snippets/servers/lowlevel/lifespan.py

@@ -0,0 +1,102 @@
+"""Run from the repository root:
+uv run examples/snippets/servers/lowlevel/lifespan.py
+"""
+
+from collections.abc import AsyncIterator
+from contextlib import asynccontextmanager
+from typing import TypedDict
+
+import mcp_types as types
+
+import mcp.server.stdio
+from mcp.server import Server, ServerRequestContext
+
+
+# Mock database class for example
+class Database:
+    """Mock database class for example."""
+
+    @classmethod
+    async def connect(cls) -> "Database":
+        """Connect to database."""
+        print("Database connected")
+        return cls()
+
+    async def disconnect(self) -> None:
+        """Disconnect from database."""
+        print("Database disconnected")
+
+    async def query(self, query_str: str) -> list[dict[str, str]]:
+        """Execute a query."""
+        # Simulate database query
+        return [{"id": "1", "name": "Example", "query": query_str}]
+
+
+class AppContext(TypedDict):
+    db: Database
+
+
+@asynccontextmanager
+async def server_lifespan(_server: Server[AppContext]) -> AsyncIterator[AppContext]:
+    """Manage server startup and shutdown lifecycle."""
+    db = await Database.connect()
+    try:
+        yield {"db": db}
+    finally:
+        await db.disconnect()
+
+
+async def handle_list_tools(
+    ctx: ServerRequestContext[AppContext], params: types.PaginatedRequestParams | None
+) -> types.ListToolsResult:
+    """List available tools."""
+    return types.ListToolsResult(
+        tools=[
+            types.Tool(
+                name="query_db",
+                description="Query the database",
+                input_schema={
+                    "type": "object",
+                    "properties": {"query": {"type": "string", "description": "SQL query to execute"}},
+                    "required": ["query"],
+                },
+            )
+        ]
+    )
+
+
+async def handle_call_tool(
+    ctx: ServerRequestContext[AppContext], params: types.CallToolRequestParams
+) -> types.CallToolResult:
+    """Handle database query tool call."""
+    if params.name != "query_db":
+        raise ValueError(f"Unknown tool: {params.name}")
+
+    db = ctx.lifespan_context["db"]
+    results = await db.query((params.arguments or {})["query"])
+
+    return types.CallToolResult(content=[types.TextContent(type="text", text=f"Query results: {results}")])
+
+
+server = Server(
+    "example-server",
+    lifespan=server_lifespan,
+    on_list_tools=handle_list_tools,
+    on_call_tool=handle_call_tool,
+)
+
+
+async def run():
+    """Run the server with lifespan management."""
+    async with mcp.server.stdio.stdio_server() as (read_stream, write_stream):
+        await server.run(
+            read_stream,
+            write_stream,
+            server.create_initialization_options(),
+        )
+
+
+if __name__ == "__main__":
+    import asyncio
+
+    asyncio.run(run())