Initial analysis of copyFile readonly issue

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

Author: Copilot

src/node/__tests__/volume/copyFile-readonly.test.ts

@@ -0,0 +1,40 @@
+import { create } from '../../../__tests__/util';
+
+describe('copyFile readonly source file issue', () => {
+  it('copyFileSync on readonly source file should be allowed', () => {
+    // Arrange
+    const vol = create({
+      '/path/to/file.txt': 'some text',
+    });
+
+    vol.chmodSync('/path/to/file.txt', 0o400); // Readonly
+
+    // Act - this should NOT throw
+    vol.copyFileSync('/path/to/file.txt', '/path/to/another.txt');
+
+    // Assert
+    expect(vol.readFileSync('/path/to/file.txt', 'utf8')).toBe('some text');
+    expect(vol.readFileSync('/path/to/another.txt', 'utf8')).toBe('some text');
+  });
+
+  it('copyFile on readonly source file should be allowed', done => {
+    // Arrange
+    const vol = create({
+      '/path/to/file.txt': 'some text',
+    });
+
+    vol.chmodSync('/path/to/file.txt', 0o400); // Readonly
+
+    // Act - this should NOT throw
+    vol.copyFile('/path/to/file.txt', '/path/to/another.txt', err => {
+      try {
+        expect(err).toBeNull();
+        expect(vol.readFileSync('/path/to/file.txt', 'utf8')).toBe('some text');
+        expect(vol.readFileSync('/path/to/another.txt', 'utf8')).toBe('some text');
+        done();
+      } catch (failure) {
+        done(failure);
+      }
+    });
+  });
+});

src/node/__tests__/volume/permission-debug.test.ts

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+import { create } from '../../../__tests__/util';
+
+describe('permission debugging', () => {
+  it('debug permission check for readonly file', () => {
+    // Arrange
+    const vol = create({
+      '/test.txt': 'content',
+    });
+
+    console.log('Initial file stats:', vol.statSync('/test.txt'));
+    console.log('Initial file mode:', vol.statSync('/test.txt').mode.toString(8));
+    
+    vol.chmodSync('/test.txt', 0o400);
+    
+    console.log('After chmod 0o400 stats:', vol.statSync('/test.txt'));
+    console.log('After chmod mode:', vol.statSync('/test.txt').mode.toString(8));
+    console.log('Perm bits:', (vol.statSync('/test.txt').mode & ~0o170000).toString(8));
+    
+    // Try to see what process uid/gid are
+    console.log('Process getuid:', process.getuid ? process.getuid() : 'undefined');
+    console.log('Process getgid:', process.getgid ? process.getgid() : 'undefined');
+    
+    // Let's see the internal node
+    const core = (vol as any)._core;
+    const linkOrNode = core.getLink ? core.getLink('/test.txt') : core.root.getChild('test.txt');
+    const node = linkOrNode.getNode ? linkOrNode.getNode() : linkOrNode.node;
+    console.log('Node uid:', node.uid);
+    console.log('Node gid:', node.gid);
+    console.log('Node perm:', node.perm.toString(8));
+    console.log('Node.canRead():', node.canRead());
+    console.log('Node.canWrite():', node.canWrite());
+    
+    // This should not throw
+    expect(() => vol.readFileSync('/test.txt')).not.toThrow();
+  });
+});