function findOriginalPos()

in packages/metro/src/Server/symbolicate.js [88:129]

40 lines of code
8 McCabe index (conditional complexity)


  function findOriginalPos(
    frame: StackFrameInput,
    module: ExplodedSourceMapModule,
  ): ?Position {
    if (
      module.map == null ||
      frame.lineNumber == null ||
      frame.column == null
    ) {
      return null;
    }
    const generatedPosInModule = {
      line1Based: frame.lineNumber - module.firstLine1Based + 1,
      column0Based: frame.column,
    };
    const mappingIndex = greatestLowerBound(
      module.map,
      generatedPosInModule,
      (target, candidate) => {
        if (target.line1Based === candidate[0]) {
          return target.column0Based - candidate[1];
        }
        return target.line1Based - candidate[0];
      },
    );
    if (mappingIndex == null) {
      return null;
    }
    const mapping = module.map[mappingIndex];
    if (
      mapping[0] !== generatedPosInModule.line1Based ||
      mapping.length < 4 /* no source line/column info */
    ) {
      return null;
    }
    return {
      // $FlowFixMe: Length checks do not refine tuple unions.
      line1Based: mapping[2],
      // $FlowFixMe: Length checks do not refine tuple unions.
      column0Based: mapping[3],
    };
  }