step_into

Instructions

Implementation Reference

• src/mcp-server.js:657-694 (handler)

  The 'step_into' tool handler. It checks if the debugger is enabled (enabling it if not), verifies the debugger is paused, sends the 'Debugger.stepInto' command via the inspector, and returns a success or error message.

  server.tool(
    "step_into",
    "Steps into function calls",
    {},
    async () => {
      try {
        // Ensure debugger is enabled
        if (!inspector.debuggerEnabled) {
          await inspector.enableDebugger();
        }
        
        if (!inspector.paused) {
          return {
            content: [{
              type: "text",
              text: "Debugger is not paused at a breakpoint"
            }]
          };
        }
        
        await inspector.send('Debugger.stepInto', {});
        
        return {
          content: [{
            type: "text",
            text: "Stepped into function call"
          }]
        };
      } catch (err) {
        return {
          content: [{
            type: "text",
            text: `Error stepping into: ${err.message}`
          }]
        };
      }
    }
  );

• src/mcp-server.js:657-694 (registration)

  The tool is registered using server.tool() with the name 'step_into'. This is the standard MCP server tool registration pattern.

  server.tool(
    "step_into",
    "Steps into function calls",
    {},
    async () => {
      try {
        // Ensure debugger is enabled
        if (!inspector.debuggerEnabled) {
          await inspector.enableDebugger();
        }
        
        if (!inspector.paused) {
          return {
            content: [{
              type: "text",
              text: "Debugger is not paused at a breakpoint"
            }]
          };
        }
        
        await inspector.send('Debugger.stepInto', {});
        
        return {
          content: [{
            type: "text",
            text: "Stepped into function call"
          }]
        };
      } catch (err) {
        return {
          content: [{
            type: "text",
            text: `Error stepping into: ${err.message}`
          }]
        };
      }
    }
  );

• src/mcp-server.js:660-660 (schema)

  The schema is defined inline as an empty object {}, meaning the tool accepts no parameters.

  {},

• src/mcp-server.js:230-274 (helper)

  The Inspector.send() helper method handles sending commands (including 'Debugger.stepInto') over the WebSocket to the Node.js debugger, managing pending request queues and timeouts.

  async send(method, params) {
  	return new Promise((resolve, reject) => {
  		const timeout = setTimeout(() => {
  			reject(new Error(`Request timed out: ${method}`));
  			this.pendingRequests.delete(id);
  		}, 5000);
  		
  		const checkConnection = () => {
  			if (this.connected) {
  				try {
  					const id = Math.floor(Math.random() * 1000000);
  					this.pendingRequests.set(id, { 
  						resolve: (result) => {
  							clearTimeout(timeout);
  							resolve(result);
  						}, 
  						reject: (err) => {
  							clearTimeout(timeout);
  							reject(err);
  						} 
  					});
  					
  					this.ws.send(JSON.stringify({
  						id,
  						method,
  						params
  					}));
  				} catch (err) {
  					clearTimeout(timeout);
  					reject(err);
  				}
  			} else {
  				const connectionCheckTimer = setTimeout(checkConnection, 100);
  				// If still not connected after 3 seconds, reject the promise
  				setTimeout(() => {
  					clearTimeout(connectionCheckTimer);
  					clearTimeout(timeout);
  					reject(new Error('Not connected to debugger'));
  				}, 3000);
  			}
  		};
  		
  		checkConnection();
  	});
  }