Function applyPatch

src/patch/apply.ts:144–230

* How does noNewLineAtEndOfFile work? * * if you remove the newline from a file that had one without editing other bits: * * it creates an insertion/removal pair where the insertion has \ No new line at end of file * * if you edit a file that didn't have a new line and don't add one: * *

(
  { hunks, path }: FilePatch,
  {
    dryRun,
    cwd,
    bestEffort,
    errors,
  }: { dryRun: boolean; cwd?: string; bestEffort: boolean; errors?: string[] },
)

 */

function applyPatch(
  { hunks, path }: FilePatch,
  {
    dryRun,
    cwd,
    bestEffort,
    errors,
  }: { dryRun: boolean; cwd?: string; bestEffort: boolean; errors?: string[] },
): void {
  path = cwd ? resolve(cwd, path) : path
  // modifying the file in place
  const fileContents = fs.readFileSync(path).toString()
  const mode = fs.statSync(path).mode

  const fileLines: string[] = fileContents.split(/\n/)

  const result: Modification[][] = []

  for (const hunk of hunks) {
    let fuzzingOffset = 0
    while (true) {
      const modifications = evaluateHunk(hunk, fileLines, fuzzingOffset)
      if (modifications) {
        result.push(modifications)
        break
      }

      fuzzingOffset =
        fuzzingOffset < 0 ? fuzzingOffset * -1 : fuzzingOffset * -1 - 1

      if (Math.abs(fuzzingOffset) > 20) {
        const message = `Cannot apply hunk ${hunks.indexOf(
          hunk,
        )} for file ${relative(process.cwd(), path)}\n\`\`\`diff\n${
          hunk.source
        }\n\`\`\`\n`

        if (bestEffort) {
          errors?.push(message)
          break
        } else {
          throw new Error(message)
        }
      }
    }
  }

  if (dryRun) {
    return
  }

  let diffOffset = 0

  for (const modifications of result) {
    for (const modification of modifications) {
      switch (modification.type) {
        case "splice":
          fileLines.splice(