Fix dollar sign replacement bug in file editing (#7871)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/core/src/tools/edit.test.ts

@@ -194,6 +194,86 @@ describe('EditTool', () => {
         'hello world',
       );
     });
+
+    it('should treat $ literally and not as replacement pattern', () => {
+      const current = "price is $100 and pattern end is ' '";
+      const oldStr = 'price is $100';
+      const newStr = 'price is $200';
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe("price is $200 and pattern end is ' '");
+    });
+
+    it("should treat $' literally and not as a replacement pattern", () => {
+      const current = 'foo';
+      const oldStr = 'foo';
+      const newStr = "bar$'baz";
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe("bar$'baz");
+    });
+
+    it('should treat $& literally and not as a replacement pattern', () => {
+      const current = 'hello world';
+      const oldStr = 'hello';
+      const newStr = '$&-replacement';
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe('$&-replacement world');
+    });
+
+    it('should treat $` literally and not as a replacement pattern', () => {
+      const current = 'prefix-middle-suffix';
+      const oldStr = 'middle';
+      const newStr = 'new$`content';
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe('prefix-new$`content-suffix');
+    });
+
+    it('should treat $1, $2 capture groups literally', () => {
+      const current = 'test string';
+      const oldStr = 'test';
+      const newStr = '$1$2replacement';
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe('$1$2replacement string');
+    });
+
+    it('should use replaceAll for normal strings without problematic $ sequences', () => {
+      const current = 'normal text replacement';
+      const oldStr = 'text';
+      const newStr = 'string';
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe('normal string replacement');
+    });
+
+    it('should handle multiple occurrences with problematic $ sequences', () => {
+      const current = 'foo bar foo baz';
+      const oldStr = 'foo';
+      const newStr = "test$'end";
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe("test$'end bar test$'end baz");
+    });
+
+    it('should handle complex regex patterns with $ at end', () => {
+      const current = "| select('match', '^[sv]d[a-z]$')";
+      const oldStr = "'^[sv]d[a-z]$'";
+      const newStr = "'^[sv]d[a-z]$' # updated";
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe("| select('match', '^[sv]d[a-z]$' # updated)");
+    });
+
+    it('should handle empty replacement with problematic $ in newString', () => {
+      const current = 'test content';
+      const oldStr = 'nothing';
+      const newStr = "replacement$'text";
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe('test content'); // No replacement because oldStr not found
+    });
+
+    it('should handle $$ (escaped dollar) correctly', () => {
+      const current = 'price value';
+      const oldStr = 'value';
+      const newStr = '$$100';
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe('price $$100');
+    });
   });
 
   describe('validateToolParams', () => {

packages/core/src/tools/edit.ts

@@ -33,6 +33,7 @@ import type {
   ModifyContext,
 } from './modifiable-tool.js';
 import { IdeClient } from '../ide/ide-client.js';
+import { safeLiteralReplace } from '../utils/textUtils.js';
 
 export function applyReplacement(
   currentContent: string | null,
@@ -51,7 +52,9 @@ export function applyReplacement(
   if (oldString === '' && !isNewFile) {
     return currentContent;
   }
-  return currentContent.replaceAll(oldString, newString);
+
+  // Use intelligent replacement that handles $ sequences safely
+  return safeLiteralReplace(currentContent, oldString, newString);
 }
 
 /**

packages/core/src/tools/smart-edit.test.ts

@@ -42,11 +42,11 @@ import {
   type Mock,
 } from 'vitest';
 import {
-  applyReplacement,
   SmartEditTool,
   type EditToolParams,
   calculateReplacement,
 } from './smart-edit.js';
+import { applyReplacement } from './edit.js';
 import { type FileDiff, ToolConfirmationOutcome } from './tools.js';
 import { ToolErrorType } from './tool-error.js';
 import path from 'node:path';
@@ -172,6 +172,22 @@ describe('SmartEditTool', () => {
         'hello new world new',
       );
     });
+
+    it('should treat $ literally and not as replacement pattern', () => {
+      const current = 'regex end is $ and more';
+      const oldStr = 'regex end is $';
+      const newStr = 'regex end is $ and correct';
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe('regex end is $ and correct and more');
+    });
+
+    it("should treat $' literally and not as a replacement pattern", () => {
+      const current = 'foo';
+      const oldStr = 'foo';
+      const newStr = "bar$'baz";
+      const result = applyReplacement(current, oldStr, newStr, false);
+      expect(result).toBe("bar$'baz");
+    });
   });
 
   describe('calculateReplacement', () => {

packages/core/src/tools/smart-edit.ts

@@ -30,26 +30,8 @@ import {
 } from './modifiable-tool.js';
 import { IdeClient } from '../ide/ide-client.js';
 import { FixLLMEditWithInstruction } from '../utils/llm-edit-fixer.js';
-
-export function applyReplacement(
-  currentContent: string | null,
-  oldString: string,
-  newString: string,
-  isNewFile: boolean,
-): string {
-  if (isNewFile) {
-    return newString;
-  }
-  if (currentContent === null) {
-    // Should not happen if not a new file, but defensively return empty or newString if oldString is also empty
-    return oldString === '' ? newString : '';
-  }
-  // If oldString is empty and it's not a new file, do not modify the content.
-  if (oldString === '' && !isNewFile) {
-    return currentContent;
-  }
-  return currentContent.replaceAll(oldString, newString);
-}
+import { applyReplacement } from './edit.js';
+import { safeLiteralReplace } from '../utils/textUtils.js';
 
 interface ReplacementContext {
   params: EditToolParams;
@@ -89,7 +71,8 @@ async function calculateExactReplacement(
 
   const exactOccurrences = normalizedCode.split(normalizedSearch).length - 1;
   if (exactOccurrences > 0) {
-    let modifiedCode = normalizedCode.replaceAll(
+    let modifiedCode = safeLiteralReplace(
+      normalizedCode,
       normalizedSearch,
       normalizedReplace,
     );