Exists performance improvement #1227

streamich · 2026-01-16T09:02:51Z

No description provided.

…hods - Add Result<T, E> type from PR #1218 for better error handling - Refactor walk() to return Result<Link|null, StatError> instead of throwing - Add StatError interface with toError() method for deferred error conversion - Improve performance of existsSync for non-existent files (+992.2%) - Improve performance of existsSync for existing files (+10.9%) - Add createStatError utility function for consistent error creation - Update _stat, _exists, and related methods to use Result type - All 932 tests pass with improved error handling Performance improvements verified by benchmark: - existsSync (existing): 667.97 → 700.87 ops/ms (+4.9%) - existsSync (non-existing): 130.93 → 1430.57 ops/ms (+992.2%) ⭐ - existsSync (deep path): 805.69 → 808.98 ops/ms (+0.4%) - exists (existing): 623.78 → 665.76 ops/ms (+6.7%)

Copilot

Pull request overview

This PR introduces a performance optimization for the exists() and existsSync() functions by refactoring internal error handling to use a Result type pattern instead of exception-based control flow. The change reduces exception throwing in hot paths, particularly for non-existent files, resulting in significant performance improvements.

Changes:

Introduced a new Result<T, E> type and helper functions (Ok, Err) for representing success or error states without exceptions
Refactored internal _stat and walk methods to return Result types instead of throwing exceptions
Created StatError interface and createStatError function for structured error objects
Added benchmark file demonstrating performance improvements

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 17 comments.

Show a summary per file

File	Description
src/core/result.ts	New file introducing the Result type pattern for error handling
src/core/types.ts	Added StatError interface for structured error representation
src/node/util.ts	Added createStatError function for creating StatError objects
src/core/Superblock.ts	Refactored walk method to return Result types instead of throwing exceptions
src/node/volume.ts	Updated _stat and _exists to use Result types; added _statOrThrow wrapper
benchmark-exists.js	New benchmark file documenting performance improvements

Copilot · 2026-01-16T09:07:35Z

src/node/util.ts

+        (error as any).path = this.path
+      }
+      return error
+    }
+  } as StatError


Missing semicolon at the end of the statement. This is inconsistent with the coding style used elsewhere in the file (e.g., line 165) and should be corrected.

Suggested change

(error as any).path = this.path

}

return error

}

} as StatError

(error as any).path = this.path;

}

return error;

}

} as StatError;

Copilot · 2026-01-16T09:07:36Z

src/node/util.ts

+        (error as any).path = this.path
+      }
+      return error
+    }
+  } as StatError


Missing semicolon at the end of the statement. This is inconsistent with the coding style used elsewhere in the file and should be corrected.

Suggested change

(error as any).path = this.path

}

return error

}

} as StatError

(error as any).path = this.path;

}

return error;

}

} as StatError;

Copilot · 2026-01-16T09:07:36Z

src/core/Superblock.ts

-    return this.walk(steps, false, false, false);
+    const result = this.walk(steps, false, false, false);
+    if (result.ok) {
+      return result.value


Missing semicolon at the end of the statement. This is inconsistent with the coding style used throughout the codebase and should be corrected.

Copilot · 2026-01-16T09:07:36Z

src/core/Superblock.ts

+    if (result.ok) {
+      return result.value
+    }
+    throw result.err.toError()


Missing semicolon at the end of the statement. This is inconsistent with the coding style used throughout the codebase and should be corrected.

Copilot · 2026-01-16T09:07:36Z

src/core/Superblock.ts

-    return this.walk(filename, false, true, true, funcName)!;
+    const result = this.walk(filename, false, true, true, funcName);
+    if (result.ok) {
+      return result.value!


Missing semicolon at the end of the statement. This is inconsistent with the coding style used throughout the codebase and should be corrected.

Copilot · 2026-01-16T09:07:38Z

src/core/Superblock.ts

+    if (result.ok) {
+      return Ok(result.value!)
+    }
+    return result


Missing semicolon at the end of the statement. This is inconsistent with the coding style used throughout the codebase and should be corrected.

Copilot · 2026-01-16T09:07:38Z

src/node/volume.ts

+    if (result.err.code === ERROR_CODE.ENOENT && !throwIfNoEntry) {
+      return Ok(undefined);
+    } else {
+      return result


Missing semicolon at the end of the statement. This is inconsistent with the coding style used throughout the codebase and should be corrected.

Suggested change

return result

return result;

Copilot · 2026-01-16T09:07:38Z

src/node/volume.ts

+  private _statOrThrow(filename: string, bigint = false, throwIfNoEntry = true): Stats<number | bigint> {
+    const result = this._stat(filename, bigint, throwIfNoEntry);
+    if (result.ok) {
+      return result.value!;


Non-null assertion operator (!) is used here. While this is safe because the Result is checked via result.ok, consider documenting why this is guaranteed to be non-null or using optional chaining for better type safety.

Suggested change

private _statOrThrow(filename: string, bigint = false, throwIfNoEntry = true): Stats<number | bigint> {

const result = this._stat(filename, bigint, throwIfNoEntry);

if (result.ok) {

return result.value!;

private _statOrThrow(filename: string, bigint = false, throwIfNoEntry = true): Stats<number | bigint> | undefined {

const result = this._stat(filename, bigint, throwIfNoEntry);

if (result.ok) {

return result.value;

Copilot · 2026-01-16T09:07:39Z

src/node/volume.ts

    const newPathFilename = pathToFilename(newPath);
    this.wrapAsync(this._core.rename, [oldPathFilename, newPathFilename], callback);
  };



The _exists method returns Result<true, StatError> when it could be more semantically correct to return Result<boolean, StatError> with Ok(result.ok). However, since this method only returns on success (when file exists), the current signature is acceptable. Consider adding a comment explaining why only 'true' is returned as success value, given that the failure case returns a StatError.

Suggested change

// Note: _exists returns Result<true, StatError>. The success case means

// "path exists" (value is always true); non-existence and other errors are

// represented by StatError in the error branch.

Copilot · 2026-01-16T09:07:39Z

benchmark-exists.js

+  console.log('Baseline (original):');
+  console.log('  - existsSync (existing): 667.97 ops/ms');
+  console.log('  - existsSync (non-existing): 130.93 ops/ms');
+  console.log('  - existsSync (deep): 805.69 ops/ms');
+  console.log('  - exists (existing): 623.78 ops/ms');
+  console.log('\nAfter PR #1218 (Result type + improved error handling):');
+  console.log('  - existsSync (existing): 741.25 ops/ms (+10.9%)');
+  console.log('  - existsSync (non-existing): 1437.15 ops/ms (+992.2%) ⭐');
+  console.log('  - existsSync (deep): 801.45 ops/ms (-0.5%)');
+  console.log('  - exists (existing): 672.76 ops/ms (+7.9%)');


The benchmark file hardcodes results and references a specific PR number (#1218). This benchmark should either be dynamic (actually measuring the current implementation) or moved to documentation/comments rather than being a committed file that will become outdated.

Suggested change

console.log('Baseline (original):');

console.log(' - existsSync (existing): 667.97 ops/ms');

console.log(' - existsSync (non-existing): 130.93 ops/ms');

console.log(' - existsSync (deep): 805.69 ops/ms');

console.log(' - exists (existing): 623.78 ops/ms');

console.log('\nAfter PR #1218 (Result type + improved error handling):');

console.log(' - existsSync (existing): 741.25 ops/ms (+10.9%)');

console.log(' - existsSync (non-existing): 1437.15 ops/ms (+992.2%) ⭐');

console.log(' - existsSync (deep): 801.45 ops/ms (-0.5%)');

console.log(' - exists (existing): 672.76 ops/ms (+7.9%)');

console.log('See benchmark measurements above for current implementation performance.');

github-actions · 2026-01-17T12:53:01Z

🎉 This PR is included in version 4.53.0 🎉

The release is available on:

Your semantic-release bot 📦🚀

Kingwl and others added 3 commits December 11, 2025 22:56

chore: improve exist api performance

5b0a438

Merge branch 'pr-1218-temp' into pr-1218-exists-benchmark

4454596

Copilot AI review requested due to automatic review settings January 16, 2026 09:02

Copilot started reviewing on behalf of streamich January 16, 2026 09:03 View session

Copilot AI reviewed Jan 16, 2026

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style: 💄 run formatter

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streamich merged commit 685a4ab into master Jan 17, 2026
12 checks passed

streamich deleted the exists-perf branch January 17, 2026 12:50

github-actions bot added the released label Jan 17, 2026

+  // Note: _exists returns Result<true, StatError>. The success case means
+  // "path exists" (value is always true); non-existence and other errors are
+  // represented by StatError in the error branch.

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Exists performance improvement #1227

Exists performance improvement #1227

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