Source Map Parser

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This project implements a WebAssembly-based Source Map parser that can map JavaScript error stack traces back to source code and extract relevant context information. Developers can easily map JavaScript error stack traces back to source code for quick problem identification and resolution. This documentation aims to help developers better understand and use this tool.

MCP Integration

Note: Requires Node.js 18+ support

Option 1: Run directly with NPX

npx -y source-map-parser-mcp@latest

Option 2: Download the build artifacts

Download the corresponding version of the build artifacts from the GitHub Release page, then run:

node dist/main.es.js

Runtime Parameter Configuration

System runtime parameters can be flexibly configured through environment variables to meet the needs of different scenarios

• SOURCE_MAP_PARSER_RESOURCE_CACHE_MAX_SIZE: Sets the maximum memory space occupied by resource cache, default is 200MB. Adjusting this value appropriately can balance performance and memory usage.
• SOURCE_MAP_PARSER_CONTEXT_OFFSET_LINE: Defines the number of context code lines to display around the error location, default is 1 line. Increasing this value provides more context information, facilitating problem diagnosis.

Example:

# Set 500MB cache and display 3 lines of context
export SOURCE_MAP_PARSER_RESOURCE_CACHE_MAX_SIZE=500
export SOURCE_MAP_PARSER_CONTEXT_OFFSET_LINE=3
npx -y source-map-parser-mcp@latest

Feature Overview

1. Stack Parsing: Parse the corresponding source code location based on provided line number, column number, and Source Map file.
2. Batch Processing: Support parsing multiple stack traces simultaneously and return batch results.
3. Context Extraction: Extract context code for a specified number of lines to help developers better understand the environment where errors occur.

MCP Service Tool Description

operating_guide

Get usage instructions for the MCP service. Provides information on how to use the MCP service through chat interaction.

parse_stack

Parse stack information by providing stack traces and Source Map addresses.

Request Example

• stacks: Stack information including line number, column number, and Source Map address.
  • line: Line number, required.
  • column: Column number, required.
  • sourceMapUrl: Source Map address, required.

{
  "stacks": [
    {
      "line": 10,
      "column": 5,
      "sourceMapUrl": "https://example.com/source.map"
    }
  ]
}

Response Example

{
  "content": [
    {
      "type": "text",
      "text": "[{\"success\":true,\"token\":{\"line\":10,\"column\":5,\"sourceCode\":[{\"line\":8,\"isStackLine\":false,\"raw\":\"function foo() {\"},{\"line\":9,\"isStackLine\":false,\"raw\":\"  console.log('bar');\"},{\"line\":10,\"isStackLine\":true,\"raw\":\"  throw new Error('test');\"},{\"line\":11,\"isStackLine\":false,\"raw\":\"}\"}],\"src\":\"index.js\"}}]"
    }
  ]
}

Parsing Result Description

• success: Indicates whether the parsing was successful.
• token: The Token object returned when parsing is successful, containing source code line number, column number, context code, and other information.
• error: Error information returned when parsing fails.

Example Run

System Prompt

According to actual needs, you can use system prompts to guide the model on how to parse stack information. For security or performance reasons, some teams may not want to expose Source Maps directly to the browser for parsing, but instead process the upload path of the Source Map. For example, converting the path bar-special.js to special/bar.js.map. In this case, you can instruct the model to perform path conversion through prompt rules.

Here is an example:

# Error Stack Trace Parsing Rules

When performing source map parsing, please follow these rules:

1. If the URL contains `special`, the file should be parsed into the `special/` directory, while removing `-special` from the filename.
2. All source map files are stored in the following CDN directory:  
   `https://cdn.jsdelivr.net/gh/MasonChow/source-map-parser-mcp@main/example/`

## Examples

- Source map address for `bar-special.js`:  
  `https://cdn.jsdelivr.net/gh/MasonChow/source-map-parser-mcp@main/example/special/bar.js.map`

Runtime Example

Error Stack

Uncaught Error: This is a error
    at foo-special.js:49:34832
    at ka (foo-special.js:48:83322)
    at Vs (foo-special.js:48:98013)
    at Et (foo-special.js:48:97897)
    at Vs (foo-special.js:48:98749)
    at Et (foo-special.js:48:97897)
    at Vs (foo-special.js:48:98059)
    at sv (foo-special.js:48:110550)
    at foo-special.js:48:107925
    at MessagePort.Ot (foo-special.js:25:1635)

FAQ

1. WebAssembly Module Loading Failure

If the tool returns the following error message, please troubleshoot as follows:

parser init error: WebAssembly.instantiate(): invalid value type 'externref', enable with --experimental-wasm-reftypes @+86

1. Check Node.js Version: Ensure Node.js version is 18 or higher. If it's lower than 18, please upgrade Node.js.
2. Enable Experimental Flag: If Node.js version is 18+ but you still encounter issues, use the following command to start the tool:

   npx --node-arg=--experimental-wasm-reftypes -y source-map-parser-mcp@latest

Local Development Guide

1. Install Dependencies

Ensure Node.js and npm are installed, then run the following command to install project dependencies:

npm install

2. Link MCP Service

Run the following command to start the MCP server:

npx tsx src/main.ts

Internal Logic Overview

1. Main File Description

• stack_parser_js_sdk.js: JavaScript wrapper for the WebAssembly module, providing core stack parsing functionality.
• parser.ts: Main implementation of the parser, responsible for initializing the WebAssembly module, retrieving Source Map content, and parsing stack information.
• server.ts: Implementation of the MCP server, providing the parse_stack tool interface for external calls.

2. Modify Parsing Logic

To modify the parsing logic, edit the getSourceToken method in the parser.ts file.

3. Add New Tools

In the server.ts file, new tool interfaces can be added using the server.tool method.

Notes

1. Source Map Files: Ensure that the provided Source Map file address is accessible and the file format is correct.
2. Error Handling: During parsing, network errors, file format errors, and other issues may be encountered; it's recommended to implement proper error handling when making calls.

Contribution Guidelines

Contributions via Issues and Pull Requests are welcome to improve this project.

License

This project is licensed under the MIT License. See the LICENSE file for details.