fix str replace bug

Author: charleslien

backend/src/__tests__/process-str-replace.test.ts

@@ -1,4 +1,5 @@
 import { describe, expect, it } from 'bun:test'
+import { applyPatch } from 'diff'
 
 import { processStrReplace } from '../process-str-replace'
 
@@ -106,21 +107,6 @@ describe('processStrReplace', () => {
     }
   })
 
-  it('should return error when oldStr is empty and file does not exist', async () => {
-    const newContent = 'const x = 1;\nconst y = 2;\n'
-    const result = await processStrReplace(
-      'test.ts',
-      [{ old: '', new: newContent, allowMultiple: false }],
-      Promise.resolve(null),
-    )
-
-    expect(result).not.toBeNull()
-    expect('error' in result).toBe(true)
-    if ('error' in result) {
-      expect(result.error).toContain('old string was empty')
-    }
-  })
-
   it('should return error if no changes were made', async () => {
     const initialContent = 'const x = 1;\nconst y = 2;\n'
     const oldStr = 'const z = 3;' // This string doesn't exist in the content
@@ -403,4 +389,31 @@ function test3() {
       }
     })
   })
+
+  it('should handle applying multiple replacements on nearby lines', async () => {
+    const initialContent = 'line 1\nline 2\nline 3\n'
+    const replacements = [
+      {
+        old: 'line 2\n',
+        new: 'this is a new line\n',
+        allowMultiple: false,
+      },
+      {
+        old: 'line 3\n',
+        new: 'new line 3\n',
+        allowMultiple: false,
+      },
+    ]
+
+    const result = await processStrReplace(
+      'test.ts',
+      replacements,
+      Promise.resolve(initialContent),
+    )
+
+    expect('content' in result).toBe(true)
+    expect(applyPatch(initialContent, (result as any).patch)).toBe(
+      'line 1\nthis is a new line\nnew line 3\n',
+    )
+  })
 })

backend/src/process-str-replace.ts

@@ -18,11 +18,20 @@ export async function processStrReplace(
   | { tool: 'str_replace'; path: string; error: string }
 > {
   const initialContent = await initialContentPromise
+  if (initialContent === null) {
+    return {
+      tool: 'str_replace',
+      path,
+      error:
+        'The file does not exist, skipping. Please use the write_file tool to create the file.',
+    }
+  }
 
   // Process each old/new string pair
   let currentContent = initialContent
   let allPatches: string[] = []
   let messages: string[] = []
+  const lineEnding = currentContent.includes('\r\n') ? '\r\n' : '\n'
 
   for (const { old: oldStr, new: newStr, allowMultiple } of replacements) {
     // Regular case: require oldStr for replacements
@@ -32,14 +41,7 @@ export async function processStrReplace(
       )
       continue
     }
-    if (currentContent === null) {
-      messages.push(
-        'The file does not exist, skipping. Please use the write_file tool to create the file.',
-      )
-      continue
-    }
 
-    const lineEnding = currentContent.includes('\r\n') ? '\r\n' : '\n'
     const normalizeLineEndings = (str: string) => str.replace(/\r\n/g, '\n')
     const normalizedCurrentContent = normalizeLineEndings(currentContent)
     const normalizedOldStr = normalizeLineEndings(oldStr)
@@ -64,20 +66,11 @@ export async function processStrReplace(
         ? normalizedCurrentContent
         : normalizedCurrentContent.replaceAll(updatedOldStr, newStr)
 
-    let patch = createPatch(path, normalizedCurrentContent, updatedContent)
-    const lines = patch.split('\n')
-    const hunkStartIndex = lines.findIndex((line) => line.startsWith('@@'))
-    if (hunkStartIndex !== -1) {
-      patch = lines.slice(hunkStartIndex).join('\n')
-      patch = patch.replaceAll('\n', lineEnding)
-      allPatches.push(patch)
-    }
-
     // Update current content for next iteration
     currentContent = updatedContent.replaceAll('\n', lineEnding)
   }
 
-  if (allPatches.length === 0) {
+  if (initialContent === currentContent) {
     logger.debug(
       {
         path,
@@ -93,7 +86,15 @@ export async function processStrReplace(
     }
   }
 
-  const finalPatch = allPatches.join('\n')
+  let patch = createPatch(path, initialContent, currentContent)
+  const lines = patch.split('\n')
+  const hunkStartIndex = lines.findIndex((line) => line.startsWith('@@'))
+  if (hunkStartIndex !== -1) {
+    patch = lines.slice(hunkStartIndex).join('\n')
+    patch = patch.replaceAll('\n', lineEnding)
+    allPatches.push(patch)
+  }
+  const finalPatch = patch
 
   logger.debug(
     {