Function getPatchForEdits

src/tools/FileEditTool/utils.ts:262–350

({
  filePath,
  fileContents,
  edits,
}: {
  filePath: string
  fileContents: string
  edits: FileEdit[]
})

 * NOTE: The returned patch is to be used for display purposes only - it has spaces instead of tabs
 */
export function getPatchForEdits({
  filePath,
  fileContents,
  edits,
}: {
  filePath: string
  fileContents: string
  edits: FileEdit[]
}): { patch: StructuredPatchHunk[]; updatedFile: string } {
  let updatedFile = fileContents
  const appliedNewStrings: string[] = []

  // Special case for empty files.
  if (
    !fileContents &&
    edits.length === 1 &&
    edits[0] &&
    edits[0].old_string === '' &&
    edits[0].new_string === ''
  ) {
    const patch = getPatchForDisplay({
      filePath,
      fileContents,
      edits: [
        {
          old_string: fileContents,
          new_string: updatedFile,
          replace_all: false,
        },
      ],
    })
    return { patch, updatedFile: '' }
  }

  // Apply each edit and check if it actually changes the file
  for (const edit of edits) {
    // Strip trailing newlines from old_string before checking
    const oldStringToCheck = edit.old_string.replace(/\n+$/, '')

    // Check if old_string is a substring of any previously applied new_string
    for (const previousNewString of appliedNewStrings) {
      if (
        oldStringToCheck !== '' &&
        previousNewString.includes(oldStringToCheck)
      ) {
        throw new Error(
          'Cannot edit file: old_string is a substring of a new_string from a previous edit.',
        )
      }
    }

    const previousContent = updatedFile
    updatedFile =
      edit.old_string === ''
        ? edit.new_string
        : applyEditToFile(
            updatedFile,
            edit.old_string,