Function normalizeFileEditInput

src/tools/FileEditTool/utils.ts:581–657

({
  file_path,
  edits,
}: {
  file_path: string
  edits: EditInput[]
})

 * Returns the normalized input if successful, or the original input if not
 */
export function normalizeFileEditInput({
  file_path,
  edits,
}: {
  file_path: string
  edits: EditInput[]
}): {
  file_path: string
  edits: EditInput[]
} {
  if (edits.length === 0) {
    return { file_path, edits }
  }

  // Markdown uses two trailing spaces as a hard line break — stripping would
  // silently change semantics. Skip stripTrailingWhitespace for .md/.mdx.
  const isMarkdown = /\.(md|mdx)$/i.test(file_path)

  try {
    const fullPath = expandPath(file_path)

    // Use cached file read to avoid redundant I/O operations.
    // If the file doesn't exist, readFileSyncCached throws ENOENT which the
    // catch below handles by returning the original input (no TOCTOU pre-check).
    const fileContent = readFileSyncCached(fullPath)

    return {
      file_path,
      edits: edits.map(({ old_string, new_string, replace_all }) => {
        const normalizedNewString = isMarkdown
          ? new_string
          : stripTrailingWhitespace(new_string)

        // If exact string match works, keep it as is
        if (fileContent.includes(old_string)) {
          return {
            old_string,
            new_string: normalizedNewString,
            replace_all,
          }
        }

        // Try de-sanitize string if exact match fails
        const { result: desanitizedOldString, appliedReplacements } =
          desanitizeMatchString(old_string)

        if (fileContent.includes(desanitizedOldString)) {
          // Apply the same exact replacements to new_string
          let desanitizedNewString = normalizedNewString
          for (const { from, to } of appliedReplacements) {
            desanitizedNewString = desanitizedNewString.replaceAll(from, to)
          }

          return {
            old_string: desanitizedOldString,
            new_string: desanitizedNewString,
            replace_all,
          }