function composeSourceMaps()

in packages/metro-source-map/src/composeSourceMaps.js [23:83]

• 55 lines of code
• 5 McCabe index (conditional complexity)

function composeSourceMaps(
  maps: $ReadOnlyArray<MixedSourceMap>,
): MixedSourceMap {
  // NOTE: require() here to break dependency cycle
  const SourceMetadataMapConsumer = require('metro-symbolicate/src/SourceMetadataMapConsumer');
  if (maps.length < 1) {
    throw new Error('composeSourceMaps: Expected at least one map');
  }
  const firstMap = maps[0];

  const consumers = maps
    .map(function (map) {
      return new Consumer(map);
    })
    .reverse();

  const generator = new SourceMapGenerator({
    file: consumers[0].file,
  });

  consumers[0].eachMapping(mapping => {
    const original = findOriginalPosition(
      consumers,
      mapping.generatedLine,
      mapping.generatedColumn,
    );
    generator.addMapping({
      generated: {
        line: mapping.generatedLine,
        column: mapping.generatedColumn,
      },
      original:
        original.line != null
          ? {
              line: original.line,
              column: original.column,
            }
          : null,
      source: original.source,
      name: original.name,
    });
  });

  const composedMap = generator.toJSON();

  composedMap.sourcesContent = composedMap.sources.map(source =>
    consumers[consumers.length - 1].sourceContentFor(source, true),
  );
  if (composedMap.sourcesContent.every(content => content == null)) {
    delete composedMap.sourcesContent;
  }
  const metadataConsumer = new SourceMetadataMapConsumer(firstMap);
  composedMap.x_facebook_sources = metadataConsumer.toArray(
    composedMap.sources,
  );
  const function_offsets = maps[maps.length - 1].x_hermes_function_offsets;
  if (function_offsets) {
    composedMap.x_hermes_function_offsets = function_offsets;
  }
  return composedMap;
}