mozilla / mozilla/source-map

Issue in consumer.originalPositionFor method is returning the lineNumber of next line of code in NextJs

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JavaScript
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Description

So, I have implemented the source-map package and I am trying to find the lineNumber and originalFile of the production error from the JS chunk. I have implemented in in create-react-app and it's working fine.

But when I am implementing it in NextJS it's returning the lineNumber of the next piece of code where the error is getting generated.
For eg: If the error is introduced in lineNumber 45 and then next piece of code is written in lineNumber 50, in between line number 45 and 50 is space then I am getting line Number as 50 from consumer.originalPositionFor.

Implementation Details:

Implemented Source Map package like this :
rawSourceMap -- is the source map file for JS chunk where the error occurred.
Getting this info from the first frame of the error stack trace.

const consumer = await new SourceMapConsumer(rawSourceMap);
const originalPosition = consumer.originalPositionFor({
  line: lineNumber,
  column: columnNumber,
});
return originalPosition;

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start at consumer.originalPositionFor and inspect the supplied lineNumber, columnNumber, and rawSourceMap from the first stack frame. Reproduce with a Next.js-generated chunk and compare mappings around the reported blank lines; done means there is a minimal fixture with a confirmed expected mapping or a documented limitation.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, next.js
Domain
devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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