Source maps mapping looks wrong when using Webpack

外部の test-source-maps プロジェクトから始め、issue に示されている generatedPositionFor() と originalPositionFor() の呼び出しと併せて dist/bundle.js.map を調査します。返されたマッピングを source-map API の想定および Webpack の設定と比較します。ラウンドトリップが有効かどうかを判断するか、再現可能なマッピング／設定の不具合を特定できれば完了です。

Hello,
I've been experimenting with this repository. I tried to generate a simple project to use source maps using Webpack: https://github.com/eloparco/test-source-maps, where I produce a js bundle starting from Typescript and I want to use source maps for the mapping between the two.

I tried to play around with the generated source maps:

const SourceMapConsumer = require("source-map").SourceMapConsumer;
const fs = require("fs");

const SOURCEMAP_ABSOUTE_PATH = "/path/to/test-source-maps/dist/bundle.js.map";
const ORIGINAL_ABSOLUTE_PATH = "/path/to/test-source-maps/src/index.ts";
const GENERATED_ABSOLUTE_PATH = "/path/to/test-source-maps/dist/bundle.js";
const ORIGINAL_LINE = 11;

let json = JSON.parse(fs.readFileSync(SOURCEMAP_ABSOUTE_PATH).toString());

SourceMapConsumer.with(json, null, (consumer) => {
  console.log(consumer.sources);

  const generated = consumer.generatedPositionFor({
    source: ORIGINAL_ABSOLUTE_PATH,
    line: ORIGINAL_LINE,
    column: 0,
  });
  console.log(generated);

  const original = consumer.originalPositionFor({
    line: generated.line,
    column: generated.column,
  });
  console.log(original);

  assert(original.line === ORIGINAL_LINE); // <------------ This assertion fails!!!
});

Here I use generatedPositionFor() to get the mapping from the original .ts file to the corresponding .js file. Then, I try to do the opposite and feed the line and column previously retrieved to originalPositionFor(), expecting it to return the original line/column that I passed to generatedPositionFor(). But that doesn't happen.

Is my understanding of source maps wrong? Or am I doing something wrong in the Webpack configuration?
Thanks