Function applySedEdit

src/tools/BashTool/BashTool.tsx:360–419

* Applies a simulated sed edit directly instead of running sed. * This is used by the permission dialog to ensure what the user previews * is exactly what gets written to the file.

(simulatedEdit: {
  filePath: string;
  newContent: string;
}, toolUseContext: SimulatedSedEditContext, parentMessage?: AssistantMessage)

 * is exactly what gets written to the file.
 */
async function applySedEdit(simulatedEdit: {
  filePath: string;
  newContent: string;
}, toolUseContext: SimulatedSedEditContext, parentMessage?: AssistantMessage): Promise<SimulatedSedEditResult> {
  const {
    filePath,
    newContent
  } = simulatedEdit;
  const absoluteFilePath = expandPath(filePath);
  const fs = getFsImplementation();

  // Read original content for VS Code notification
  const encoding = detectFileEncoding(absoluteFilePath);
  let originalContent: string;
  try {
    originalContent = await fs.readFile(absoluteFilePath, {
      encoding
    });
  } catch (e) {
    if (isENOENT(e)) {
      return {
        data: {
          stdout: '',
          stderr: `sed: ${filePath}: No such file or directory\nExit code 1`,
          interrupted: false
        }
      };
    }
    throw e;
  }

  // Track file history before making changes (for undo support)
  if (fileHistoryEnabled() && parentMessage) {
    await fileHistoryTrackEdit(toolUseContext.updateFileHistoryState, absoluteFilePath, parentMessage.uuid);
  }

  // Detect line endings and write new content
  const endings = detectLineEndings(absoluteFilePath);
  writeTextContent(absoluteFilePath, newContent, encoding, endings);

  // Notify VS Code about the file change
  notifyVscodeFileUpdated(absoluteFilePath, originalContent, newContent);

  // Update read timestamp to invalidate stale writes
  toolUseContext.readFileState.set(absoluteFilePath, {
    content: newContent,
    timestamp: getFileModificationTime(absoluteFilePath),
    offset: undefined,
    limit: undefined
  });

  // Return success result matching sed output format (sed produces no output on success)
  return {
    data: {
      stdout: '',
      stderr: '',
      interrupted: false
    }