Implement `realpath.native` support for memfs by Copilot · Pull Request #1117 · streamich/memfs

Copilot · 2025-07-26T23:22:09Z

This PR adds support for fs.realpath.native() and fs.realpathSync.native() to memfs, bringing full compatibility with Node.js filesystem API.

What's Added

fs.realpath.native(path[, options], callback) - Asynchronous native realpath
fs.realpathSync.native(path[, options]) - Synchronous native realpath

Both methods support the same parameter combinations as Node.js:

Path as string, Buffer, or URL
Optional encoding options (string or object with encoding property)
Full error handling and callback patterns

Implementation Details

The implementation delegates to the existing realpathBase method used by regular realpath functions. This is appropriate since memfs operates as a virtual filesystem and doesn't require actual native system calls. The native methods behave identically to their regular counterparts.

Key changes:

Added realpathNative and realpathNativeSync methods to Volume class
Extended TypeScript interfaces (FsCallbackApi, FsSynchronousApi, IFs) to include native methods
Updated createFsFromVolume to bind native methods as properties of realpath functions
Added comprehensive test coverage for all parameter combinations and edge cases

Example Usage

const { fs } = require('memfs');

// Setup filesystem
fs.mkdirSync('/app');
fs.writeFileSync('/app/index.js', 'console.log("Hello")');
fs.symlinkSync('/app', '/link');

// Use native realpath methods
fs.realpath.native('/link/index.js', (err, resolved) => {
  console.log(resolved); // '/app/index.js'
});

const resolved = fs.realpathSync.native('/link/index.js');
console.log(resolved); // '/app/index.js'

Testing

Added 23 comprehensive tests covering:

Async and sync variants with various parameter combinations
Different encoding options (utf8, buffer)
Error handling for non-existent paths and permission issues
Comparison with regular realpath methods to ensure identical behavior
Edge cases like deep symlink chains and root path resolution

All existing tests continue to pass (1075 tests total, 0 regressions).

Fixes #1116.

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

streamich

Implement only realpath.native and realpathSync.native, make them reuse functionality of realpath and realpathSync, where possible. Do not implement realPathNative and realpathNativeSync.

Refactor realpath to be a Volume member set in constructor, and attach .native to it:

class Volume {
  // ...
   constructor() {
     // ...
     this.realpath = function ralpath() {};
     this.realpath.native = () => {};
   }

When done, reformat codebase with yarn prettier.

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

Copilot · 2025-07-27T09:27:37Z

Implement only realpath.native and realpathSync.native, make them reuse functionality of realpath and realpathSync, where possible. Do not implement realPathNative and realpathNativeSync.
...

I've refactored the implementation as requested:

Removed realpathNative and realpathNativeSync methods from the Volume class
Refactored realpath and realpathSync to be constructor-assigned functions with .native properties
Updated TypeScript interfaces and API lists accordingly
Updated tests to use the new .native syntax
Ran prettier to reformat the codebase

The implementation now follows the pattern you specified where realpath.native and realpathSync.native are properties of the main functions, all set up in the constructor.

Commit: 4390275

streamich

Make sure native variants are also created in createFsFromVolume().

Make sure tests pass yarn test.

Make sure to run yarn prettier.

streamich · 2025-07-27T09:56:15Z

+    const realpathImpl = (
+      path: PathLike,
+      a: TCallback<TDataOut> | opts.IRealpathOptions | string,
+      b?: TCallback<TDataOut>,
+    ) => {
+      const [opts, callback] = getRealpathOptsAndCb(a, b);
+      const pathFilename = pathToFilename(path);
+      self.wrapAsync(self.realpathBase, [pathFilename, opts.encoding], callback);
+    };
+
+    const realpathNativeImpl = (
+      path: PathLike,
+      a: TCallback<TDataOut> | opts.IRealpathOptions | string,
+      b?: TCallback<TDataOut>,
+    ) => {
+      const [opts, callback] = getRealpathOptsAndCb(a, b);
+      const pathFilename = pathToFilename(path);
+      self.wrapAsync(self.realpathBase, [pathFilename, opts.encoding], callback);
+    };


Are these two functions the same? If so, reuse just one.

Fixed in commit cf7a19f. Consolidated the duplicate implementations - now using the same function for both regular and native variants since they are identical. Both realpathImpl and realpathSyncImpl are reused for their respective .native properties.

streamich · 2025-07-27T09:56:21Z


    this.root = root;
+
+    // Set up realpath as function properties with native variants


Remove this comment.

Removed the comment in commit cf7a19f.

streamich · 2025-07-27T09:56:27Z

  WriteStream: new (...args) => IWriteStream;
  FSWatcher: new () => FSWatcher;

+  // realpath function properties with native variants


Remove this comment.

Removed the comment in commit cf7a19f.

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

Copilot · 2025-07-27T10:08:32Z

Make sure native variants are also created in createFsFromVolume().

Make sure tests pass yarn test.
...

Fixed in commit cf7a19f. Updated createFsFromVolume() to properly handle the .native properties for both realpath and realpathSync functions. The native variants are now correctly bound as properties of the main functions in the created filesystem interface.

streamich

LGTM

github-actions · 2025-07-27T10:18:13Z

🎉 This PR is included in version 4.22.0 🎉

The release is available on:

Your semantic-release bot 📦🚀

Initial plan

402c11e

Copilot AI assigned Copilot and streamich Jul 26, 2025

Copilot started work on behalf of streamich July 26, 2025 23:22 View session

Implement realpath.native support for memfs

70172d9

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

Copilot AI changed the title ~~[WIP] Implement realpath.native~~ Implement realpath.native support for memfs Jul 26, 2025

Copilot AI requested a review from streamich July 26, 2025 23:48

Copilot finished work on behalf of streamich July 26, 2025 23:48

streamich marked this pull request as ready for review July 27, 2025 08:42

streamich requested changes Jul 27, 2025

View reviewed changes

Copilot started work on behalf of streamich July 27, 2025 09:08 View session

Refactor realpath to use constructor pattern with native properties

4390275

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

Copilot AI requested a review from streamich July 27, 2025 09:29

Copilot finished work on behalf of streamich July 27, 2025 09:29

streamich requested changes Jul 27, 2025

View reviewed changes

Copilot started work on behalf of streamich July 27, 2025 09:57 View session

Fix createFsFromVolume and consolidate duplicate implementations

cf7a19f

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

Copilot AI requested a review from streamich July 27, 2025 10:09

Copilot finished work on behalf of streamich July 27, 2025 10:09

streamich approved these changes Jul 27, 2025

View reviewed changes

streamich merged commit 89d7e54 into master Jul 27, 2025
12 checks passed

streamich deleted the copilot/fix-1116 branch July 27, 2025 10:15

github-actions bot added the released label Jul 27, 2025


		this.root = root;

		// Set up realpath as function properties with native variants

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Copilot AI commented Jul 26, 2025 •

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