@jridgewell/trace-mapping

Trace the original position through a source map

trace-mapping allows you to take the line and column of an output file and trace it to the original location in the source file through a source map.

You may already be familiar with the source-map package's SourceMapConsumer. This provides the same originalPositionFor and generatedPositionFor API, without requiring WASM.

Installation

npm install @jridgewell/trace-mapping

Usage

import { TraceMap, originalPositionFor, generatedPositionFor } from '@jridgewell/trace-mapping';

const tracer = new TraceMap({
  version: 3,
  sources: ['input.js'],
  names: ['foo'],
  mappings: 'KAyCIA',
});

// Lines start at line 1, columns at column 0.
const traced = originalPositionFor(tracer, { line: 1, column: 5 });
assert.deepEqual(traced, {
  source: 'input.js',
  line: 42,
  column: 4,
  name: 'foo',
});

const generated = generatedPositionFor(tracer, {
  source: 'input.js',
  line: 42,
  column: 4,
});
assert.deepEqual(generated, {
  line: 1,
  column: 5,
});

We also provide a lower level API to get the actual segment that matches our line and column. Unlike originalPositionFor, traceSegment uses a 0-base for line:

SectionedSourceMaps

The sourcemap spec defines a special sections field that's designed to handle concatenation of output code with associated sourcemaps. This type of sourcemap is rarely used (no major build tool produces it), but if you are hand coding a concatenation you may need it. We provide an AnyMap helper that can receive either a regular sourcemap or a SectionedSourceMap and returns a TraceMap instance:

Benchmarks

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