Merge pull request #2851 from olaservo/fix-wsl-path-conversion

Resolve filesystem issue where WSL paths are incorrectly converted to Windows format

Author: olaservo

src/filesystem/__tests__/path-utils.test.ts

@@ -10,14 +10,25 @@ describe('Path Utilities', () => {
         .toBe('/home/user/some path');
     });
 
-    it('converts WSL paths to Windows format', () => {
+    it('never converts WSL paths (they work correctly in WSL with Node.js fs)', () => {
+      // WSL paths should NEVER be converted, regardless of platform
+      // They are valid Linux paths that work with Node.js fs operations inside WSL
       expect(convertToWindowsPath('/mnt/c/NS/MyKindleContent'))
-        .toBe('C:\\NS\\MyKindleContent');
+        .toBe('/mnt/c/NS/MyKindleContent');
+      expect(convertToWindowsPath('/mnt/d/Documents'))
+        .toBe('/mnt/d/Documents');
     });
 
-    it('converts Unix-style Windows paths to Windows format', () => {
-      expect(convertToWindowsPath('/c/NS/MyKindleContent'))
-        .toBe('C:\\NS\\MyKindleContent');
+    it('converts Unix-style Windows paths only on Windows platform', () => {
+      // On Windows, /c/ style paths should be converted
+      if (process.platform === 'win32') {
+        expect(convertToWindowsPath('/c/NS/MyKindleContent'))
+          .toBe('C:\\NS\\MyKindleContent');
+      } else {
+        // On Linux, leave them unchanged
+        expect(convertToWindowsPath('/c/NS/MyKindleContent'))
+          .toBe('/c/NS/MyKindleContent');
+      }
     });
 
     it('leaves Windows paths unchanged but ensures backslashes', () => {
@@ -34,11 +45,20 @@ describe('Path Utilities', () => {
         .toBe('C:\\Program Files\\Some App');
     });
 
-    it('handles uppercase and lowercase drive letters', () => {
+    it('handles drive letter paths based on platform', () => {
+      // WSL paths should never be converted
       expect(convertToWindowsPath('/mnt/d/some/path'))
-        .toBe('D:\\some\\path');
-      expect(convertToWindowsPath('/d/some/path'))
-        .toBe('D:\\some\\path');
+        .toBe('/mnt/d/some/path');
+
+      if (process.platform === 'win32') {
+        // On Windows, Unix-style paths like /d/ should be converted
+        expect(convertToWindowsPath('/d/some/path'))
+          .toBe('D:\\some\\path');
+      } else {
+        // On Linux, /d/ is just a regular Unix path
+        expect(convertToWindowsPath('/d/some/path'))
+          .toBe('/d/some/path');
+      }
     });
   });
 
@@ -67,21 +87,33 @@ describe('Path Utilities', () => {
         .toBe('C:\\NS\\MyKindleContent');
     });
 
-    it('handles WSL paths', () => {
+    it('always preserves WSL paths (they work correctly in WSL)', () => {
+      // WSL paths should ALWAYS be preserved, regardless of platform
+      // This is the fix for issue #2795
       expect(normalizePath('/mnt/c/NS/MyKindleContent'))
-        .toBe('C:\\NS\\MyKindleContent');
+        .toBe('/mnt/c/NS/MyKindleContent');
+      expect(normalizePath('/mnt/d/Documents'))
+        .toBe('/mnt/d/Documents');
     });
 
     it('handles Unix-style Windows paths', () => {
-      expect(normalizePath('/c/NS/MyKindleContent'))
-        .toBe('C:\\NS\\MyKindleContent');
+      // On Windows, /c/ paths should be converted
+      if (process.platform === 'win32') {
+        expect(normalizePath('/c/NS/MyKindleContent'))
+          .toBe('C:\\NS\\MyKindleContent');
+      } else if (process.platform === 'linux') {
+        // On Linux, /c/ is just a regular Unix path
+        expect(normalizePath('/c/NS/MyKindleContent'))
+          .toBe('/c/NS/MyKindleContent');
+      }
     });
 
     it('handles paths with spaces and mixed slashes', () => {
       expect(normalizePath('C:/NS/My Kindle Content'))
         .toBe('C:\\NS\\My Kindle Content');
+      // WSL paths should always be preserved
       expect(normalizePath('/mnt/c/NS/My Kindle Content'))
-        .toBe('C:\\NS\\My Kindle Content');
+        .toBe('/mnt/c/NS/My Kindle Content');
       expect(normalizePath('C:\\Program Files (x86)\\App Name'))
         .toBe('C:\\Program Files (x86)\\App Name');
       expect(normalizePath('"C:\\Program Files\\App Name"'))
@@ -91,10 +123,19 @@ describe('Path Utilities', () => {
     });
 
     it('preserves spaces in all path formats', () => {
+      // WSL paths should always be preserved
       expect(normalizePath('/mnt/c/Program Files/App Name'))
-        .toBe('C:\\Program Files\\App Name');
-      expect(normalizePath('/c/Program Files/App Name'))
-        .toBe('C:\\Program Files\\App Name');
+        .toBe('/mnt/c/Program Files/App Name');
+
+      if (process.platform === 'win32') {
+        // On Windows, Unix-style paths like /c/ should be converted
+        expect(normalizePath('/c/Program Files/App Name'))
+          .toBe('C:\\Program Files\\App Name');
+      } else {
+        // On Linux, /c/ is just a regular Unix path
+        expect(normalizePath('/c/Program Files/App Name'))
+          .toBe('/c/Program Files/App Name');
+      }
       expect(normalizePath('C:/Program Files/App Name'))
         .toBe('C:\\Program Files\\App Name');
     });
@@ -105,15 +146,16 @@ describe('Path Utilities', () => {
         .toBe('C:\\NS\\Sub&Folder');
       expect(normalizePath('C:/NS/Sub&Folder'))
         .toBe('C:\\NS\\Sub&Folder');
+      // WSL paths should always be preserved
       expect(normalizePath('/mnt/c/NS/Sub&Folder'))
-        .toBe('C:\\NS\\Sub&Folder');
-      
+        .toBe('/mnt/c/NS/Sub&Folder');
+
       // Test tilde in path (short names in Windows)
       expect(normalizePath('C:\\NS\\MYKIND~1'))
         .toBe('C:\\NS\\MYKIND~1');
       expect(normalizePath('/Users/NEMANS~1/FOLDER~2/SUBFO~1/Public/P12PST~1'))
         .toBe('/Users/NEMANS~1/FOLDER~2/SUBFO~1/Public/P12PST~1');
-      
+
       // Test other special characters
       expect(normalizePath('C:\\Path with #hash'))
         .toBe('C:\\Path with #hash');
@@ -128,10 +170,19 @@ describe('Path Utilities', () => {
     it('capitalizes lowercase drive letters for Windows paths', () => {
       expect(normalizePath('c:/windows/system32'))
         .toBe('C:\\windows\\system32');
-      expect(normalizePath('/mnt/d/my/folder')) // WSL path with lowercase drive
-        .toBe('D:\\my\\folder');
-      expect(normalizePath('/e/another/folder')) // Unix-style Windows path with lowercase drive
-        .toBe('E:\\another\\folder');
+      // WSL paths should always be preserved
+      expect(normalizePath('/mnt/d/my/folder'))
+        .toBe('/mnt/d/my/folder');
+
+      if (process.platform === 'win32') {
+        // On Windows, Unix-style paths should be converted and capitalized
+        expect(normalizePath('/e/another/folder'))
+          .toBe('E:\\another\\folder');
+      } else {
+        // On Linux, /e/ is just a regular Unix path
+        expect(normalizePath('/e/another/folder'))
+          .toBe('/e/another/folder');
+      }
     });
 
     it('handles UNC paths correctly', () => {
@@ -172,4 +223,132 @@ describe('Path Utilities', () => {
       expect(expandHome('C:/test')).toBe('C:/test');
     });
   });
+
+  describe('WSL path handling (issue #2795 fix)', () => {
+    // Save original platform
+    const originalPlatform = process.platform;
+
+    afterEach(() => {
+      // Restore platform after each test
+      Object.defineProperty(process, 'platform', {
+        value: originalPlatform,
+        writable: true,
+        configurable: true
+      });
+    });
+
+    it('should NEVER convert WSL paths - they work correctly in WSL with Node.js fs', () => {
+      // The key insight: When running `wsl npx ...`, Node.js runs INSIDE WSL (process.platform === 'linux')
+      // and /mnt/c/ paths work correctly with Node.js fs operations in that environment.
+      // Converting them to C:\ format breaks fs operations because Windows paths don't work inside WSL.
+
+      // Mock Linux platform (inside WSL)
+      Object.defineProperty(process, 'platform', {
+        value: 'linux',
+        writable: true,
+        configurable: true
+      });
+
+      // WSL paths should NOT be converted, even inside WSL
+      expect(normalizePath('/mnt/c/Users/username/folder'))
+        .toBe('/mnt/c/Users/username/folder');
+
+      expect(normalizePath('/mnt/d/Documents/project'))
+        .toBe('/mnt/d/Documents/project');
+    });
+
+    it('should also preserve WSL paths when running on Windows', () => {
+      // Mock Windows platform
+      Object.defineProperty(process, 'platform', {
+        value: 'win32',
+        writable: true,
+        configurable: true
+      });
+
+      // WSL paths should still be preserved (though they wouldn't be accessible from Windows Node.js)
+      expect(normalizePath('/mnt/c/Users/username/folder'))
+        .toBe('/mnt/c/Users/username/folder');
+
+      expect(normalizePath('/mnt/d/Documents/project'))
+        .toBe('/mnt/d/Documents/project');
+    });
+
+    it('should convert Unix-style Windows paths (/c/) only when running on Windows (win32)', () => {
+      // Mock process.platform to be 'win32' (Windows)
+      Object.defineProperty(process, 'platform', {
+        value: 'win32',
+        writable: true,
+        configurable: true
+      });
+
+      // Unix-style Windows paths like /c/ should be converted on Windows
+      expect(normalizePath('/c/Users/username/folder'))
+        .toBe('C:\\Users\\username\\folder');
+
+      expect(normalizePath('/d/Documents/project'))
+        .toBe('D:\\Documents\\project');
+    });
+
+    it('should NOT convert Unix-style paths (/c/) when running inside WSL (linux)', () => {
+      // Mock process.platform to be 'linux' (WSL/Linux)
+      Object.defineProperty(process, 'platform', {
+        value: 'linux',
+        writable: true,
+        configurable: true
+      });
+
+      // When on Linux, /c/ is just a regular Unix directory, not a drive letter
+      expect(normalizePath('/c/some/path'))
+        .toBe('/c/some/path');
+
+      expect(normalizePath('/d/another/path'))
+        .toBe('/d/another/path');
+    });
+
+    it('should preserve regular Unix paths on all platforms', () => {
+      // Test on Linux
+      Object.defineProperty(process, 'platform', {
+        value: 'linux',
+        writable: true,
+        configurable: true
+      });
+
+      expect(normalizePath('/home/user/documents'))
+        .toBe('/home/user/documents');
+
+      expect(normalizePath('/var/log/app'))
+        .toBe('/var/log/app');
+
+      // Test on Windows (though these paths wouldn't work on Windows)
+      Object.defineProperty(process, 'platform', {
+        value: 'win32',
+        writable: true,
+        configurable: true
+      });
+
+      expect(normalizePath('/home/user/documents'))
+        .toBe('/home/user/documents');
+
+      expect(normalizePath('/var/log/app'))
+        .toBe('/var/log/app');
+    });
+
+    it('reproduces exact scenario from issue #2795', () => {
+      // Simulate running inside WSL: wsl npx @modelcontextprotocol/server-filesystem /mnt/c/Users/username/folder
+      Object.defineProperty(process, 'platform', {
+        value: 'linux',
+        writable: true,
+        configurable: true
+      });
+
+      // This is the exact path from the issue
+      const inputPath = '/mnt/c/Users/username/folder';
+      const result = normalizePath(inputPath);
+
+      // Should NOT convert to C:\Users\username\folder
+      expect(result).toBe('/mnt/c/Users/username/folder');
+      expect(result).not.toContain('C:');
+      expect(result).not.toContain('\\');
+    });
+  });
 });

src/filesystem/path-utils.ts

@@ -8,14 +8,15 @@ import os from 'os';
  */
 export function convertToWindowsPath(p: string): string {
   // Handle WSL paths (/mnt/c/...)
+  // NEVER convert WSL paths - they are valid Linux paths that work with Node.js fs operations in WSL
+  // Converting them to Windows format (C:\...) breaks fs operations inside WSL
   if (p.startsWith('/mnt/')) {
-    const driveLetter = p.charAt(5).toUpperCase();
-    const pathPart = p.slice(6).replace(/\//g, '\\');
-    return `${driveLetter}:${pathPart}`;
+    return p; // Leave WSL paths unchanged
   }
-  
+
   // Handle Unix-style Windows paths (/c/...)
-  if (p.match(/^\/[a-zA-Z]\//)) {
+  // Only convert when running on Windows
+  if (p.match(/^\/[a-zA-Z]\//) && process.platform === 'win32') {
     const driveLetter = p.charAt(1).toUpperCase();
     const pathPart = p.slice(2).replace(/\//g, '\\');
     return `${driveLetter}:${pathPart}`;
@@ -38,21 +39,29 @@ export function convertToWindowsPath(p: string): string {
 export function normalizePath(p: string): string {
   // Remove any surrounding quotes and whitespace
   p = p.trim().replace(/^["']|["']$/g, '');
-  
-  // Check if this is a Unix path (starts with / but not a Windows or WSL path)
-  const isUnixPath = p.startsWith('/') && 
-                    !p.match(/^\/mnt\/[a-z]\//i) && 
-                    !p.match(/^\/[a-zA-Z]\//);
-  
+
+  // Check if this is a Unix path that should not be converted
+  // WSL paths (/mnt/) should ALWAYS be preserved as they work correctly in WSL with Node.js fs
+  // Regular Unix paths should also be preserved
+  const isUnixPath = p.startsWith('/') && (
+    // Always preserve WSL paths (/mnt/c/, /mnt/d/, etc.)
+    p.match(/^\/mnt\/[a-z]\//i) ||
+    // On non-Windows platforms, treat all absolute paths as Unix paths
+    (process.platform !== 'win32') ||
+    // On Windows, preserve Unix paths that aren't Unix-style Windows paths (/c/, /d/, etc.)
+    (process.platform === 'win32' && !p.match(/^\/[a-zA-Z]\//))
+  );
+
   if (isUnixPath) {
     // For Unix paths, just normalize without converting to Windows format
     // Replace double slashes with single slashes and remove trailing slashes
     return p.replace(/\/+/g, '/').replace(/\/+$/, '');
   }
-  
-  // Convert WSL or Unix-style Windows paths to Windows format
+
+  // Convert Unix-style Windows paths (/c/, /d/) to Windows format if on Windows
+  // This function will now leave /mnt/ paths unchanged
   p = convertToWindowsPath(p);
-  
+
   // Handle double backslashes, preserving leading UNC \\
   if (p.startsWith('\\\\')) {
     // For UNC paths, first normalize any excessive leading backslashes to exactly \\
@@ -67,15 +76,15 @@ export function normalizePath(p: string): string {
     // For non-UNC paths, normalize all double backslashes
     p = p.replace(/\\\\/g, '\\');
   }
-  
+
   // Use Node's path normalization, which handles . and .. segments
   let normalized = path.normalize(p);
-  
+
   // Fix UNC paths after normalization (path.normalize can remove a leading backslash)
   if (p.startsWith('\\\\') && !normalized.startsWith('\\\\')) {
     normalized = '\\' + normalized;
   }
-  
+
   // Handle Windows paths: convert slashes and ensure drive letter is capitalized
   if (normalized.match(/^[a-zA-Z]:/)) {
     let result = normalized.replace(/\//g, '\\');
@@ -85,10 +94,15 @@ export function normalizePath(p: string): string {
     }
     return result;
   }
-  
-  // For all other paths (including relative paths), convert forward slashes to backslashes
-  // This ensures relative paths like "some/relative/path" become "some\\relative\\path"
-  return normalized.replace(/\//g, '\\');
+
+  // On Windows, convert forward slashes to backslashes for relative paths
+  // On Linux/Unix, preserve forward slashes
+  if (process.platform === 'win32') {
+    return normalized.replace(/\//g, '\\');
+  }
+
+  // On non-Windows platforms, keep the normalized path as-is
+  return normalized;
 }
 
 /**