fix(files): bound expanded edit output

Author: icecrasher321

apps/sim/lib/copilot/tools/server/files/edit-content.ts

@@ -17,6 +17,7 @@ import {
   EditContentError,
   type WorkspaceFileContentEdit,
 } from '@/lib/workspace-files/edit-content'
+import { MAX_WORKSPACE_FILE_CONTENT_BYTES } from '@/lib/workspace-files/orchestration'
 import {
   collectSimPageDiagnostics,
   HAND_WRITTEN_PAGE_MESSAGE,
@@ -205,7 +206,9 @@ export const editContentServerTool: BaseServerTool<EditContentArgs, EditContentR
             return { success: false, message: `Unknown patch strategy: "${intent.edit.strategy}"` }
           }
           try {
-            finalContent = applyWorkspaceFileContentEdit(existing, edit)
+            finalContent = applyWorkspaceFileContentEdit(existing, edit, {
+              maxOutputBytes: MAX_WORKSPACE_FILE_CONTENT_BYTES,
+            })
           } catch (error) {
             if (error instanceof EditContentError) {
               return {

apps/sim/lib/copilot/tools/server/files/file-preview.ts

@@ -53,7 +53,7 @@ function extractPatchPreview(
     const search = typeof edit?.search === 'string' ? edit.search : ''
     if (!search) return undefined
     if (edit?.replaceAll === true) {
-      return existingContent.split(search).join(streamedContent)
+      return existingContent.replaceAll(search, streamedContent)
     }
     const firstIdx = existingContent.indexOf(search)
     if (firstIdx === -1) return undefined

apps/sim/lib/workspace-files/application/edit-workspace-file-content.test.ts

@@ -236,4 +236,13 @@ describe('editWorkspaceFileContent', () => {
     ).rejects.toThrow(/lines 1, 3/)
     expect(mockUpdateStoredContent).not.toHaveBeenCalled()
   })
+
+  it('rejects an oversized replaceAll result before writing it', async () => {
+    mockFetchWorkspaceFileBuffer.mockResolvedValue(Buffer.from('a'.repeat(1_100_000), 'utf-8'))
+
+    await expect(
+      edit({ mode: 'search_replace', search: 'a', content: 'x'.repeat(49), replaceAll: true })
+    ).rejects.toMatchObject({ code: 'payload_too_large' })
+    expect(mockUpdateStoredContent).not.toHaveBeenCalled()
+  })
 })

apps/sim/lib/workspace-files/application/edit-workspace-file-content.ts

@@ -131,11 +131,17 @@ export const editWorkspaceFileContent = defineAuthorizedWorkspaceFileUseCase({
       const before = buffer.toString('utf-8')
       let after: string
       try {
-        after = applyWorkspaceFileContentEdit(before, input.edit)
+        after = applyWorkspaceFileContentEdit(before, input.edit, {
+          maxOutputBytes: MAX_WORKSPACE_FILE_CONTENT_BYTES,
+        })
       } catch (error) {
         if (error instanceof EditContentError) {
           throw new OrchestrationError(
-            error.failure.reason === 'not_found' ? 'not_found' : 'validation',
+            error.failure.reason === 'not_found'
+              ? 'not_found'
+              : error.failure.reason === 'output_too_large'
+                ? 'payload_too_large'
+                : 'validation',
             error.message
           )
         }

apps/sim/lib/workspace-files/edit-content.test.ts

@@ -69,6 +69,12 @@ describe('applyStringReplacement', () => {
   it('replaces every non-overlapping match when explicitly requested', () => {
     expect(applyStringReplacement('a a a', 'a', 'b', true)).toBe('b b b')
   })
+
+  it('rejects an oversized replaceAll result before constructing it', () => {
+    expect(() =>
+      applyStringReplacement('aaaa', 'a', '0123456789', true, { maxOutputBytes: 20 })
+    ).toThrow(/exceeds the 20 byte limit/)
+  })
 })
 
 describe('applyWorkspaceFileContentEdit', () => {

apps/sim/lib/workspace-files/edit-content.ts

@@ -1,9 +1,16 @@
+import { Buffer } from 'node:buffer'
+
 export type EditContentFailure =
   | { reason: 'empty_search' }
   | { reason: 'not_found' }
   | { reason: 'ambiguous'; lineNumbers: number[] }
   | { reason: 'invalid_occurrence' }
   | { reason: 'invalid_anchor_order' }
+  | { reason: 'output_too_large'; maxBytes: number }
+
+export interface EditContentOptions {
+  maxOutputBytes?: number
+}
 
 export class EditContentError extends Error {
   constructor(
@@ -61,6 +68,30 @@ function scanMatches(text: string, search: string): MatchScan {
   return { count, lineNumbers }
 }
 
+function assertReplacementOutputWithinLimit(
+  text: string,
+  search: string,
+  content: string,
+  count: number,
+  maxOutputBytes: number | undefined
+): void {
+  if (maxOutputBytes === undefined) return
+
+  const retainedBytes = Buffer.byteLength(text) - count * Buffer.byteLength(search)
+  const replacementBytes = Buffer.byteLength(content)
+  const availableReplacementBytes = maxOutputBytes - retainedBytes
+  const exceedsLimit =
+    availableReplacementBytes < 0 ||
+    (replacementBytes > 0 && count > Math.floor(availableReplacementBytes / replacementBytes))
+
+  if (exceedsLimit) {
+    throw new EditContentError(`Edit result exceeds the ${maxOutputBytes} byte limit`, {
+      reason: 'output_too_large',
+      maxBytes: maxOutputBytes,
+    })
+  }
+}
+
 /**
  * Replaces the single occurrence of `search`, or refuses.
  *
@@ -72,7 +103,8 @@ export function applyStringReplacement(
   text: string,
   search: string,
   content: string,
-  replaceAll = false
+  replaceAll = false,
+  options?: EditContentOptions
 ): string {
   if (search.length === 0) {
     throw new EditContentError('Search text cannot be empty', { reason: 'empty_search' })
@@ -94,7 +126,15 @@ export function applyStringReplacement(
     )
   }
 
-  if (replaceAll) return text.split(search).join(content)
+  assertReplacementOutputWithinLimit(
+    text,
+    search,
+    content,
+    replaceAll ? count : 1,
+    options?.maxOutputBytes
+  )
+
+  if (replaceAll) return text.replaceAll(search, content)
 
   const index = text.indexOf(search)
   return text.slice(0, index) + content + text.slice(index + search.length)
@@ -188,10 +228,11 @@ function contentLines(content: string): string[] {
  */
 export function applyWorkspaceFileContentEdit(
   text: string,
-  edit: WorkspaceFileContentEdit
+  edit: WorkspaceFileContentEdit,
+  options?: EditContentOptions
 ): string {
   if (edit.mode === 'search_replace') {
-    return applyStringReplacement(text, edit.search, edit.content, edit.replaceAll)
+    return applyStringReplacement(text, edit.search, edit.content, edit.replaceAll, options)
   }
 
   const lines = splitLines(text)