Function applyHunk

src/patch/apply.ts:156–265

* Checks if the hunk can be made to fit at the provided location with at most `maxErrors` * insertions, substitutions, or deletions, while ensuring also that: * - lines deleted in the hunk match exactly, and * - wherever an insertion operation or block of insertion operations appears in the

(
    hunkLines: string[],
    toPos: number,
    maxErrors: number,
    hunkLinesI: number = 0,
    lastContextLineMatched: boolean = true,
    patchedLines: string[] = [],
    patchedLinesLength: number = 0
  )

   * `replacementLines`. Otherwise, returns null.
   */
  function applyHunk(
    hunkLines: string[],
    toPos: number,
    maxErrors: number,
    hunkLinesI: number = 0,
    lastContextLineMatched: boolean = true,
    patchedLines: string[] = [],
    patchedLinesLength: number = 0
  ): ApplyHunkReturnType | null {
    let nConsecutiveOldContextLines = 0;
    let nextContextLineMustMatch = false;
    for (; hunkLinesI < hunkLines.length; hunkLinesI++) {
      const hunkLine = hunkLines[hunkLinesI],
          operation = (hunkLine.length > 0 ? hunkLine[0] : ' '),
          content = (hunkLine.length > 0 ? hunkLine.substr(1) : hunkLine);

      if (operation === '-') {
        if (compareLine(toPos + 1, lines[toPos], operation, content)) {
          toPos++;
          nConsecutiveOldContextLines = 0;
        } else {
          if (!maxErrors || lines[toPos] == null) {
            return null;
          }
          patchedLines[patchedLinesLength] = lines[toPos];
          return applyHunk(
            hunkLines,
            toPos + 1,
            maxErrors - 1,
            hunkLinesI,
            false,
            patchedLines,
            patchedLinesLength + 1
          );
        }
      }

      if (operation === '+') {
        if (!lastContextLineMatched) {
          return null;
        }
        patchedLines[patchedLinesLength] = content;
        patchedLinesLength++;
        nConsecutiveOldContextLines = 0;
        nextContextLineMustMatch = true;
      }

      if (operation === ' ') {
        nConsecutiveOldContextLines++;
        patchedLines[patchedLinesLength] = lines[toPos];
        if (compareLine(toPos + 1, lines[toPos], operation, content)) {
          patchedLinesLength++;
          lastContextLineMatched = true;
          nextContextLineMustMatch = false;
          toPos++;
        } else {
          if (nextContextLineMustMatch || !maxErrors) {
            return null;