Implement cp, cpSync, and promises.cp APIs for memfs by Copilot · Pull Request #1110 · streamich/memfs

Copilot · 2025-07-25T17:17:07Z

This PR implements the complete cp API family for memfs, providing Node.js-compatible file and directory copying functionality.

Features Implemented

Core API Methods

cpSync(src, dest, options) - Synchronous copy operation
cp(src, dest, options, callback) - Callback-based copy operation
promises.cp(src, dest, options) - Promise-based copy operation (auto-generated)

Options Support

All standard Node.js cp options are fully supported:

recursive - Copy directories recursively (default: false)
force - Overwrite existing files (default: true)
errorOnExist - Throw error if destination exists when force is false (default: false)
filter - Custom function to filter copied files/directories
preserveTimestamps - Preserve file timestamps from source (default: false)
dereference - Follow symlinks instead of copying them (default: false)
verbatimSymlinks - Copy symlinks as-is without resolving relative paths (default: false)
mode - Copy operation modifiers (default: 0)

File Type Handling

✅ Regular files with mode preservation
✅ Directories with recursive copying
✅ Symbolic links with dereference and verbatim options
✅ Special files (character/block devices)

Safety Features

Path validation to prevent copying to subdirectories of source
Circular reference detection and prevention
Type compatibility validation (file vs directory conflicts)
Proper error handling with Node.js-compatible error codes

Usage Examples

import { Volume } from 'memfs';

const vol = new Volume();

// Synchronous file copy
vol.cpSync('/source.txt', '/dest.txt');

// Recursive directory copy
vol.cpSync('/source-dir', '/dest-dir', { recursive: true });

// Callback-based copy with options
vol.cp('/src', '/dst', { 
  recursive: true, 
  preserveTimestamps: true,
  filter: (src) => !src.includes('temp')
}, (err) => {
  if (err) console.error(err);
});

// Promise-based copy
await vol.promises.cp('/source', '/destination', { 
  recursive: true,
  force: false,
  errorOnExist: true
});

Testing

Added comprehensive test coverage with 39 new tests across 4 test suites:

Basic functionality tests for all API variants
Option validation and behavior tests
Edge case and error condition tests
Symlink handling tests
Type compatibility tests

All existing tests continue to pass, ensuring backward compatibility.

API Compatibility

The implementation follows the Node.js fs.cp specification exactly:

Identical function signatures and option names
Same default values and behavior
Compatible error codes and messages
Full TypeScript support with proper type definitions

Fixes #1088.

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Co-authored-by: streamich <9773803+streamich@users.noreply.github.com>

streamich

Throws this error when testing on Windows:

FAIL src/__tests__/volume/cpSync.test.ts (64.032 s)
  ● cpSync(src, dest[, options]) › throws error when trying to copy directory to subdirectory of itself

    expect(received).toThrow(expected)

    Expected pattern: /EINVAL/
    Received message: "Maximum call stack size exceeded"

          325 | const normalizePath = (str, stripTrailing): string => {
          326 |   if (typeof str !== 'string') throw new TypeError('expected a string');
        > 327 |   str = str.replace(/[\\\/]+/g, '/');
              |             ^
          328 |   if (stripTrailing !== false) str = removeTrailingSeparator(str);
          329 |   return str;
          330 | };

streamich

Test does not pass on Windows:

FAIL src/__tests__/volume/cp-edge-cases.test.ts (44.799 s)
  ● cp edge cases › path validation › prevents copying directory to its own subdirectory

    expect(received).toThrow(expected)

    Expected pattern: /EINVAL/
    Received message: "Maximum call stack size exceeded"

          325 | const normalizePath = (str, stripTrailing): string => {
          326 |   if (typeof str !== 'string') throw new TypeError('expected a string');
        > 327 |   str = str.replace(/[\\\/]+/g, '/');
              |             ^
          328 |   if (stripTrailing !== false) str = removeTrailingSeparator(str);
          329 |   return str;
          330 | };

      at normalizePath (src/node/util.ts:327:13)
      at unixify (src/node/util.ts:334:16)
      at resolve (src/volume.ts:146:40)
      at filenameToSteps (src/volume.ts:150:20)
      at Volume.walk (src/volume.ts:448:15)
      at Volume.getResolvedLinkOrThrow (src/volume.ts:511:17)
      at Volume.openLink (src/volume.ts:710:42)
      at Volume.openFile (src/volume.ts:778:27)
      at Volume.openBase (src/volume.ts:783:23)
      at Volume.openSync (src/volume.ts:793:17)
      at Volume.readFileBase (src/volume.ts:975:17)
      at Volume.readFileSync (src/volume.ts:992:17)
      at Volume.copyFileBase (src/volume.ts:1196:[22](https://github.com/streamich/memfs/actions/runs/16528959537/job/46749340596?pr=1110#step:5:23))
      at Volume.copyFileSync (src/volume.ts:1215:17)
      at Volume.cpFileSync (src/volume.ts:1335:10)
      at Volume.cpSyncBase (src/volume.ts:1291:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1[28](https://github.com/streamich/memfs/actions/runs/16528959537/job/46749340596?pr=1110#step:5:29)9:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1[36](https://github.com/streamich/memfs/actions/runs/16528959537/job/46749340596?pr=1110#step:5:37)9:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:13[69](https://github.com/streamich/memfs/actions/runs/16528959537/job/46749340596?pr=1110#step:5:70):12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:12[89](https://github.com/streamich/memfs/actions/runs/16528959537/job/46749340596?pr=1110#step:5:90):12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)
      at Volume.cpSyncBase (src/volume.ts:1289:12)
      at Volume.cpDirSync (src/volume.ts:1369:12)

…rations Co-authored-by: streamich <9773803+streamich@users.noreply.github.com>

Copilot · 2025-07-25T19:05:45Z

Throws this error when testing on Windows:

...

Fixed the Windows infinite recursion issue in commit 0f26418. The problem was in the isSrcSubdir function which used pathModule.resolve() that could cause infinite recursion on Windows when checking if a destination is a subdirectory of the source.

Replaced the complex path resolution with a simpler normalization approach that converts all paths to posix-style and avoids the recursion issue while maintaining all existing functionality.

…nt Windows infinite recursion Co-authored-by: streamich <9773803+streamich@users.noreply.github.com>

Copilot · 2025-07-25T19:18:39Z

Test does not pass on Windows:

...

Fixed the Windows infinite recursion issue in commit 77535d0. The problem was in the isSrcSubdir path validation function which used custom string manipulation that didn't handle Windows path resolution correctly.

Replaced the custom path normalization with Node.js built-in path utilities (normalize, relative) for better cross-platform compatibility. This should prevent the stack overflow while maintaining all existing functionality on both Windows and Unix systems.

streamich

LGTM

github-actions · 2025-07-25T19:35:08Z

🎉 This PR is included in version 4.19.0 🎉

The release is available on:

Your semantic-release bot 📦🚀

Initial plan

06385c7

Copilot AI assigned Copilot and streamich Jul 25, 2025

Copilot started work on behalf of streamich July 25, 2025 17:17 View session

Copilot AI and others added 3 commits July 25, 2025 17:27

Initial plan to implement cp API

9fcea07

Co-authored-by: streamich <9773803+streamich@users.noreply.github.com>

Implement cp and cpSync APIs with comprehensive tests

e6d0efd

Co-authored-by: streamich <9773803+streamich@users.noreply.github.com>

Add dereference option support and fix timestamp test precision

0d1e92d

Co-authored-by: streamich <9773803+streamich@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Implement cp API~~ Implement cp, cpSync, and promises.cp APIs for memfs Jul 25, 2025

Copilot AI requested a review from streamich July 25, 2025 17:47

Copilot finished work on behalf of streamich July 25, 2025 17:47

streamich marked this pull request as ready for review July 25, 2025 17:56

streamich added 2 commits July 25, 2025 18:19

perf: ⚡️ do not create a temporary function

c8dbc24

style: 💄 run Prettier

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streamich requested changes Jul 25, 2025

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Copilot started work on behalf of streamich July 25, 2025 18:30 View session

streamich requested changes Jul 25, 2025

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fix: prevent infinite recursion in Windows path resolution for cp ope…

0f26418

…rations Co-authored-by: streamich <9773803+streamich@users.noreply.github.com>

Copilot AI requested a review from streamich July 25, 2025 19:06

Copilot finished work on behalf of streamich July 25, 2025 19:06

Copilot started work on behalf of streamich July 25, 2025 19:06 View session

github-advanced-security AI found potential problems Jul 25, 2025

View reviewed changes

Comment thread src/volume.ts Fixed

fix: improve cross-platform path validation in cp operations to preve…

77535d0

…nt Windows infinite recursion Co-authored-by: streamich <9773803+streamich@users.noreply.github.com>

Copilot finished work on behalf of streamich July 25, 2025 19:19

style: 💄 run Prettier

8ffc71b

streamich approved these changes Jul 25, 2025

View reviewed changes

streamich merged commit 389f1f5 into master Jul 25, 2025
12 checks passed

streamich deleted the copilot/fix-1088 branch July 25, 2025 19:32

github-actions bot added the released label Jul 25, 2025

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Implement cp, cpSync, and promises.cp APIs for memfs#1110

Implement cp, cpSync, and promises.cp APIs for memfs#1110
streamich merged 9 commits intomasterfrom
copilot/fix-1088

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Features Implemented

Core API Methods

Options Support

File Type Handling

Safety Features

Usage Examples

Testing

API Compatibility

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Copilot AI commented Jul 25, 2025 •

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