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refactor: update file write operations to use copy instead of rename … #3218

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refactor: update file write operations to use copy instead of rename … #3218

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86 changes: 46 additions & 40 deletions src/filesystem/__tests__/lib.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -399,18 +399,19 @@ describe('Lib Functions', () => {
{ oldText: 'line2', newText: 'modified line2' }
];

mockFs.rename.mockResolvedValueOnce(undefined);

mockFs.copyFile.mockResolvedValueOnce(undefined);
mockFs.unlink.mockResolvedValueOnce(undefined);

const result = await applyFileEdits('/test/file.txt', edits, false);

expect(result).toContain('modified line2');
// Should write to temporary file then rename
// Should write to temporary file then copy
expect(mockFs.writeFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.txt\.[a-f0-9]+\.tmp$/),
'line1\nmodified line2\nline3\n',
'utf-8'
);
expect(mockFs.rename).toHaveBeenCalledWith(
expect(mockFs.copyFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.txt\.[a-f0-9]+\.tmp$/),
'/test/file.txt'
);
Expand All @@ -432,39 +433,41 @@ describe('Lib Functions', () => {
{ oldText: 'line1', newText: 'first line' },
{ oldText: 'line3', newText: 'third line' }
];

mockFs.rename.mockResolvedValueOnce(undefined);


mockFs.copyFile.mockResolvedValueOnce(undefined);
mockFs.unlink.mockResolvedValueOnce(undefined);

await applyFileEdits('/test/file.txt', edits, false);

expect(mockFs.writeFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.txt\.[a-f0-9]+\.tmp$/),
'first line\nline2\nthird line\n',
'utf-8'
);
expect(mockFs.rename).toHaveBeenCalledWith(
expect(mockFs.copyFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.txt\.[a-f0-9]+\.tmp$/),
'/test/file.txt'
);
});

it('handles whitespace-flexible matching', async () => {
mockFs.readFile.mockResolvedValue(' line1\n line2\n line3\n');

const edits = [
{ oldText: 'line2', newText: 'modified line2' }
];

mockFs.rename.mockResolvedValueOnce(undefined);


mockFs.copyFile.mockResolvedValueOnce(undefined);
mockFs.unlink.mockResolvedValueOnce(undefined);

await applyFileEdits('/test/file.txt', edits, false);

expect(mockFs.writeFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.txt\.[a-f0-9]+\.tmp$/),
' line1\n modified line2\n line3\n',
'utf-8'
);
expect(mockFs.rename).toHaveBeenCalledWith(
expect(mockFs.copyFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.txt\.[a-f0-9]+\.tmp$/),
'/test/file.txt'
);
Expand All @@ -481,71 +484,74 @@ describe('Lib Functions', () => {

it('handles complex multi-line edits with indentation', async () => {
mockFs.readFile.mockResolvedValue('function test() {\n console.log("hello");\n return true;\n}');

const edits = [
{
oldText: ' console.log("hello");\n return true;',
newText: ' console.log("world");\n console.log("test");\n return false;'
{
oldText: ' console.log("hello");\n return true;',
newText: ' console.log("world");\n console.log("test");\n return false;'
}
];

mockFs.rename.mockResolvedValueOnce(undefined);


mockFs.copyFile.mockResolvedValueOnce(undefined);
mockFs.unlink.mockResolvedValueOnce(undefined);

await applyFileEdits('/test/file.js', edits, false);

expect(mockFs.writeFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.js\.[a-f0-9]+\.tmp$/),
'function test() {\n console.log("world");\n console.log("test");\n return false;\n}',
'utf-8'
);
expect(mockFs.rename).toHaveBeenCalledWith(
expect(mockFs.copyFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.js\.[a-f0-9]+\.tmp$/),
'/test/file.js'
);
});

it('handles edits with different indentation patterns', async () => {
mockFs.readFile.mockResolvedValue(' if (condition) {\n doSomething();\n }');

const edits = [
{
oldText: 'doSomething();',
newText: 'doSomethingElse();\n doAnotherThing();'
{
oldText: 'doSomething();',
newText: 'doSomethingElse();\n doAnotherThing();'
}
];

mockFs.rename.mockResolvedValueOnce(undefined);


mockFs.copyFile.mockResolvedValueOnce(undefined);
mockFs.unlink.mockResolvedValueOnce(undefined);

await applyFileEdits('/test/file.js', edits, false);

expect(mockFs.writeFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.js\.[a-f0-9]+\.tmp$/),
' if (condition) {\n doSomethingElse();\n doAnotherThing();\n }',
'utf-8'
);
expect(mockFs.rename).toHaveBeenCalledWith(
expect(mockFs.copyFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.js\.[a-f0-9]+\.tmp$/),
'/test/file.js'
);
});

it('handles CRLF line endings in file content', async () => {
mockFs.readFile.mockResolvedValue('line1\r\nline2\r\nline3\r\n');

const edits = [
{ oldText: 'line2', newText: 'modified line2' }
];

mockFs.rename.mockResolvedValueOnce(undefined);


mockFs.copyFile.mockResolvedValueOnce(undefined);
mockFs.unlink.mockResolvedValueOnce(undefined);

await applyFileEdits('/test/file.txt', edits, false);

expect(mockFs.writeFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.txt\.[a-f0-9]+\.tmp$/),
'line1\nmodified line2\nline3\n',
'utf-8'
);
expect(mockFs.rename).toHaveBeenCalledWith(
expect(mockFs.copyFile).toHaveBeenCalledWith(
expect.stringMatching(/\/test\/file\.txt\.[a-f0-9]+\.tmp$/),
'/test/file.txt'
);
Expand Down
22 changes: 10 additions & 12 deletions src/filesystem/lib.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -142,18 +142,17 @@ export async function writeFileContent(filePath: string, content: string): Promi
await fs.writeFile(filePath, content, { encoding: "utf-8", flag: 'wx' });
} catch (error) {
if ((error as NodeJS.ErrnoException).code === 'EEXIST') {
// Security: Use atomic rename to prevent race conditions where symlinks
// could be created between validation and write. Rename operations
// replace the target file atomically and don't follow symlinks.
// Security: Write to temp file first, then copy to target.
// This prevents partial writes if an error occurs mid-operation.
// The temp file is always cleaned up in the finally block.
const tempPath = `${filePath}.${randomBytes(16).toString('hex')}.tmp`;
try {
await fs.writeFile(tempPath, content, 'utf-8');
await fs.rename(tempPath, filePath);
} catch (renameError) {
await fs.copyFile(tempPath, filePath);
} finally {
try {
await fs.unlink(tempPath);
} catch {}
throw renameError;
}
} else {
throw error;
Expand Down Expand Up @@ -240,18 +239,17 @@ export async function applyFileEdits(
const formattedDiff = `${'`'.repeat(numBackticks)}diff\n${diff}${'`'.repeat(numBackticks)}\n\n`;

if (!dryRun) {
// Security: Use atomic rename to prevent race conditions where symlinks
// could be created between validation and write. Rename operations
// replace the target file atomically and don't follow symlinks.
// Security: Write to temp file first, then copy to target.
// This prevents partial writes if an error occurs mid-operation.
// The temp file is always cleaned up in the finally block.
const tempPath = `${filePath}.${randomBytes(16).toString('hex')}.tmp`;
try {
await fs.writeFile(tempPath, modifiedContent, 'utf-8');
await fs.rename(tempPath, filePath);
} catch (error) {
await fs.copyFile(tempPath, filePath);
} finally {
try {
await fs.unlink(tempPath);
} catch {}
throw error;
}
}

Expand Down