Function getFunctionMapVisitor

packages/metro-source-map/src/generateFunctionMap.js:150–207

(
  context: ?Context,
  pushMapping: RangeMapping => void,
)

}

function getFunctionMapVisitor(
  context: ?Context,
  pushMapping: RangeMapping => void,
): FunctionMapVisitor {
  const nameStack: Array<{loc: BabelNodeSourceLocation, name: string}> = [];
  let tailPos = {line: 1, column: 0};
  let tailName: null | string = null;

  function advanceToPos(pos: {column: number, line: number}) {
    if (tailPos && positionGreater(pos, tailPos)) {
      const name = nameStack[0].name; // We always have at least Program
      if (name !== tailName) {
        pushMapping({
          name,
          start: {line: tailPos.line, column: tailPos.column},
        });
        tailName = name;
      }
    }
    tailPos = pos;
  }

  function pushFrame(name: string, loc: BabelNodeSourceLocation) {
    advanceToPos(loc.start);
    nameStack.unshift({name, loc});
  }

  function popFrame() {
    const top = nameStack[0];
    if (top) {
      const {loc} = top;
      advanceToPos(loc.end);
      nameStack.shift();
    }
  }

  if (!context) {
    context = {};
  }

  const basename = context.filename
    ? fsPath.basename(context.filename).replace(/\..+$/, '')
    : null;

  return {
    enter(path) {
      let name = getNameForPath(path);
      if (basename) {
        name = removeNamePrefix(name, basename);
      }
      pushFrame(name, nullthrows(path.node.loc));
    },

    exit(path) {
      popFrame();
    },
  };
}