language-server-mcp

Instructions

Implementation Reference

• src/index.ts:546-615 (handler)

  The handler function for the 'get_diagnostics' tool. It initializes an LSP server for the given language, constructs a TextDocumentItem from the provided file path and content, sets up a listener for diagnostics notifications, opens the document to trigger diagnostics, and resolves with the diagnostics or a timeout message.

  private async handleGetDiagnostics(args: any): Promise<any> {
    const { languageId, filePath, content, projectRoot } = args;
    console.log(`[handleGetDiagnostics] Processing request for ${languageId}`);
    
    const server = await this.getOrCreateServer(languageId, projectRoot);
    const actualRoot = server.workspaceRoot;
  
    const absolutePath = isAbsolute(filePath) ? filePath : join(actualRoot, filePath);
    const uri = `file://${absolutePath}`;
  
    // Ensure directory exists
    const fileDir = dirname(absolutePath);
    if (!existsSync(fileDir)) {
      mkdirSync(fileDir, { recursive: true });
    }
  
    const textDocument: TextDocumentItem = {
      uri,
      languageId,
      version: 1,
      text: content,
    };
  
    console.log(`[handleGetDiagnostics] Setting up diagnostics listener for ${uri}`);
    return new Promise((resolve) => {
      const listeners = this.diagnosticsListeners.get(uri) || [];
      const listener = (params: PublishDiagnosticsParams) => {
        console.log(`[handleGetDiagnostics] Received diagnostics for ${uri}:`, params);
        resolve({
          content: [
            {
              type: 'text',
              text: JSON.stringify(params.diagnostics, null, 2),
            },
          ],
        });
  
        // Remove listener after receiving diagnostics
        const index = listeners.indexOf(listener);
        if (index !== -1) {
          listeners.splice(index, 1);
        }
      };
      listeners.push(listener);
      this.diagnosticsListeners.set(uri, listeners);
  
      // Send document to trigger diagnostics
      console.log(`[handleGetDiagnostics] Sending document to server:`, textDocument);
      server.connection.sendNotification('textDocument/didOpen', {
        textDocument,
      } as DidOpenTextDocumentParams);
  
      // Set timeout
      setTimeout(() => {
        console.log(`[handleGetDiagnostics] Timeout reached for ${uri}`);
        const index = listeners.indexOf(listener);
        if (index !== -1) {
          listeners.splice(index, 1);
          resolve({
            content: [
              {
                type: 'text',
                text: 'No diagnostics received within timeout',
              },
            ],
          });
        }
      }, 2000);
    });
  }

• src/index.ts:360-384 (registration)

  Registers the 'get_diagnostics' tool in the MCP server tools list, including its name, description, and input schema.

    name: 'get_diagnostics',
    description: 'Get diagnostic information for a document',
    inputSchema: {
      type: 'object',
      properties: {
        languageId: { 
          type: 'string',
          description: 'The language identifier (e.g., "typescript", "javascript")'
        },
        filePath: { 
          type: 'string',
          description: 'Absolute or relative path to the source file'
        },
        content: { 
          type: 'string',
          description: 'The current content of the file'
        },
        projectRoot: { 
          type: 'string',
          description: 'Important: Root directory of the project for resolving imports and node_modules where the tsconfig.json or jsconfig.json is located'
        },
      },
      required: ['languageId', 'filePath', 'content', 'projectRoot'],
    },
  },

• src/index.ts:362-383 (schema)

  Defines the input schema for the 'get_diagnostics' tool, specifying required parameters: languageId, filePath, content, projectRoot.

  inputSchema: {
    type: 'object',
    properties: {
      languageId: { 
        type: 'string',
        description: 'The language identifier (e.g., "typescript", "javascript")'
      },
      filePath: { 
        type: 'string',
        description: 'Absolute or relative path to the source file'
      },
      content: { 
        type: 'string',
        description: 'The current content of the file'
      },
      projectRoot: { 
        type: 'string',
        description: 'Important: Root directory of the project for resolving imports and node_modules where the tsconfig.json or jsconfig.json is located'
      },
    },
    required: ['languageId', 'filePath', 'content', 'projectRoot'],
  },