Get stack trace as a string when using source map?

Question

To get as much as possible from my errors, I want to capture stack trace to display in the browser console and also to send it to an external logger service.

The first case works fine, when I console.error(myError) the source map file is interpreted correctly by the browser and the stack trace display relevant file names.

However, when I try to get the stack trace as a string with (new Error()).stack, the filenames are not relevant:

My Error
at applicationError (http://localhost:3000/static/js/main.chunk.js:29259:
at http://localhost:3000/static/js/main.chunk.js:1624:
at onError (http://localhost:3000/static/js/0.chunk.js:82415:3)
at apiCall (http://localhost:3000/static/js/0.chunk.js:82449:12)
at async http://localhost:3000/static/js/main.chunk.js:26165:21
at async App.componentWillMount (http://localhost:3000/static/js/main.chunk.js:246:5)

How can I get the "parsed" stack trace so I can send the relevant information to my logger?

I have seen these SO questions but, while the question seems relevant at first sight, none answer my question:

• Javascript: debug stack trace with source maps
• How to use source map on the JS stacktrace?

Answer 1

I had the same issue, and finally, I found this npm module: https://www.npmjs.com/package/sourcemapped-stacktrace

Example from README:

try {
  // break something
  bork();
} catch (e) {
  // pass e.stack to window.mapStackTrace
  window.mapStackTrace(e.stack, function(mappedStack) {
    // do what you want with mappedStack here
    console.log(mappedStack.join("\n"));
  }, {
    filter: function (line) {
      // process only sources containing `spec.js`
      return /(spec\.js)/.test(line);
    }
  });
}

Edit:
I was not able to get the above library to work, so I created a simple implementation for this myself. Might fail in some edge cases, and is probably not the most efficient, but for my needs it's enough.

import {RawSourceMap, SourceMapConsumer} from 'source-map-js';

const sourceMaps: {[key: string] : RawSourceMap} = {};
async function getSourceMapFromUri(uri: string) {
  if (sourceMaps[uri] != undefined) {
    return sourceMaps[uri];
  }
  const uriQuery = new URL(uri).search;
  const currentScriptContent = await (await fetch(uri)).text();

  let mapUri = RegExp(/\/\/# sourceMappingURL=(.*)/).exec(currentScriptContent)[1];
  mapUri = new URL(mapUri, uri).href + uriQuery;

  const map = await (await fetch(mapUri)).json();

  sourceMaps[uri] = map;

  return map;
}

async function mapStackTrace(stack: string) {
  const stackLines = stack.split('\n');
  const mappedStack = [];

  for (const line of stackLines) {
    const match = RegExp(/(.*)(https?:\/\/.*):(\d+):(\d+)/).exec(line);
    if (match == null) {
      mappedStack.push(line);
      continue;
    }

    const uri = match[2];
    const consumer = new SourceMapConsumer(await getSourceMapFromUri(uri));

    const originalPosition = consumer.originalPositionFor({
      line: parseInt(match[3]),
      column: parseInt(match[4]),
    });

    if (originalPosition.source == null || originalPosition.line == null || originalPosition.column == null) {
      mappedStack.push(line);
      continue;
    }

    mappedStack.push(`${originalPosition.source}:${originalPosition.line}:${originalPosition.column + 1}`);
  }

  return mappedStack.join('\n');
}

(You could also probably use the normal source-map library, I had to use source-map-js because of some bug which happens in my specific environment)