Add basic MCP server which can read files, updating README

scripts/mcp_server.py

@@ -0,0 +1,96 @@
+"""
+The Serena Model Context Protocol (MCP) Server
+"""
+
+import os
+import sys
+from abc import abstractmethod
+from collections.abc import AsyncIterator
+from contextlib import asynccontextmanager
+from dataclasses import dataclass
+from typing import cast
+
+import yaml
+from mcp.server.fastmcp.server import Context, FastMCP, Settings
+from sensai.util import logging
+
+from multilspy import SyncLanguageServer
+from multilspy.multilspy_config import Language, MultilspyConfig
+from multilspy.multilspy_logger import MultilspyLogger
+
+log = logging.getLogger(__name__)
+
+
+@dataclass
+class SerenaMCPRequestContext:
+    language_server: SyncLanguageServer
+
+
+@asynccontextmanager
+async def server_lifespan(mcp_server: FastMCP) -> AsyncIterator[SerenaMCPRequestContext]:
+    """Manage server startup and shutdown lifecycle."""
+    argv = sys.argv[1:]
+    if len(argv) != 1:
+        print("\nUsage: mcp_server <.yml project file>", file=sys.stderr)
+        sys.exit(1)
+
+    project_file = argv[0]
+    if not os.path.exists(project_file):
+        print(f"Project file not found: {project_file}", file=sys.stderr)
+        sys.exit(1)
+
+    # read project configuration
+    with open(project_file, encoding="utf-8") as f:
+        project = yaml.safe_load(f)
+    language = Language(project["language"])
+    project_root = project["project_root"]
+
+    # create and start the language server instance
+    config = MultilspyConfig(code_language=language)
+    logger = MultilspyLogger()
+    language_server = SyncLanguageServer.create(config, logger, project_root)
+    language_server.start()
+    try:
+        yield SerenaMCPRequestContext(language_server=language_server)
+    finally:
+        language_server.stop()
+
+
+mcp_settings = Settings(lifespan=server_lifespan)
+mcp = FastMCP(**mcp_settings.model_dump())
+
+
+class Tool:
+    def __init__(self, ctx: Context):
+        lifespan_context = cast(SerenaMCPRequestContext, ctx.request_context.lifespan_context)
+        self.langsrv = lifespan_context.language_server
+
+    def execute(self) -> str:
+        try:
+            return self._execute()
+        except Exception as e:
+            log.error(f"Error executing tool: {e}")
+            return f"Error executing tool: {e}"
+
+    @abstractmethod
+    def _execute(self):
+        pass
+
+
+@mcp.tool()
+def read_file(ctx: Context, relative_path: str) -> str:
+    log.info(f"read_file: {relative_path=}")
+
+    class ReadFileTool(Tool):
+        def _execute(self):
+            with self.langsrv.open_file(relative_path):
+                return self.langsrv.get_open_file_text(relative_path)
+
+    return ReadFileTool(ctx).execute()
+
+
+if __name__ == "__main__":
+    logging.basicConfig(
+        level=logging.DEBUG, stream=sys.stderr, format="%(levelname)-5s %(asctime)-15s %(name)s:%(funcName)s:%(lineno)d - %(message)s"
+    )
+    mcp.run()