Function structuredPatch

src/patch/create.ts:191–343

(
  oldFileName: string,
  newFileName: string,
  oldStr: string,
  newStr: string,
  oldHeader?: string,
  newHeader?: string,
  options?: StructuredPatchOptionsAbortable | StructuredPatchOptionsNonabortable | StructuredPatchCallbackNonabortable
)

  options?: StructuredPatchOptionsNonabortable
): StructuredPatch
export function structuredPatch(
  oldFileName: string,
  newFileName: string,
  oldStr: string,
  newStr: string,
  oldHeader?: string,
  newHeader?: string,
  options?: StructuredPatchOptionsAbortable | StructuredPatchOptionsNonabortable | StructuredPatchCallbackNonabortable
): StructuredPatch | undefined {
  let optionsObj: StructuredPatchOptionsAbortable | StructuredPatchOptionsNonabortable;
  if (!options) {
    optionsObj = {};
  } else if (typeof options === 'function') {
    optionsObj = {callback: options};
  } else {
    optionsObj = options;
  }


  if (typeof optionsObj.context === 'undefined') {
    optionsObj.context = 4;
  }

  // We copy this into its own variable to placate TypeScript, which thinks
  // optionsObj.context might be undefined in the callbacks below.
  const context = optionsObj.context;

  // @ts-expect-error (runtime check for something that is correctly a static type error)
  if (optionsObj.newlineIsToken) {
    throw new Error('newlineIsToken may not be used with patch-generation functions, only with diffing functions');
  }

  if (!optionsObj.callback) {
    return diffLinesResultToPatch(diffLines(oldStr, newStr, optionsObj as any));
  } else {
    const {callback} = optionsObj;
    diffLines(
      oldStr,
      newStr,
      {
        ...optionsObj,
        callback: (diff) => {
          const patch = diffLinesResultToPatch(diff);
          // TypeScript is unhappy without the cast because it does not understand that `patch` may
          // be undefined here only if `callback` is StructuredPatchCallbackAbortable:
          (callback as any)(patch);
        }
      }
    );
  }

  function diffLinesResultToPatch(diff: ChangeObjectPlusLines[] | undefined) {
    // STEP 1: Build up the patch with no "\ No newline at end of file" lines and with the arrays
    //         of lines containing trailing newline characters. We'll tidy up later...

    if(!diff) {
      return;
    }