Avoid repeatedly extracting source text for the copy-context hint (#26115)

src/renderer/src/components/editor/selection-copy.test.ts

@@ -1,5 +1,33 @@
 import { describe, expect, it } from 'vitest'
-import { formatCopiedSelectionWithContext, getContextualCopyLineRange } from './selection-copy'
+import {
+  canCopySelectionWithContext,
+  formatCopiedSelectionWithContext,
+  getContextualCopyLineRange
+} from './selection-copy'
+
+describe('contextual copy eligibility', () => {
+  it('matches formatting eligibility for line boundaries and whitespace-only selections', () => {
+    for (const startLineNumber of [1, 2, 44]) {
+      for (const endLineNumber of [1, 2, 3, 44, 45]) {
+        for (const endColumn of [1, 2, 15]) {
+          const selection = { startLineNumber, startColumn: 1, endLineNumber, endColumn }
+          const expected =
+            endLineNumber !== startLineNumber &&
+            (endColumn === 1 ? endLineNumber - 1 : endLineNumber) >= startLineNumber
+          expect(canCopySelectionWithContext(selection)).toBe(expected)
+          expect(
+            formatCopiedSelectionWithContext({
+              relativePath: '',
+              language: 'plaintext',
+              selection,
+              selectedText: ' \n'
+            }) !== null
+          ).toBe(expected)
+        }
+      }
+    }
+  })
+})
 
 describe('formatCopiedSelectionWithContext', () => {
   it('formats multi-line selections with file and line context', () => {

src/renderer/src/components/editor/selection-copy.ts

@@ -13,15 +13,10 @@ export function formatCopiedSelectionWithContext({
   selection,
   selectedText
 }: FormatCopiedSelectionArgs): string | null {
+  if (!canCopySelectionWithContext(selection)) {
+    return null
+  }
   const { startLine, endLine } = getContextualCopyLineRange(selection)
-  const isSingleLineSelection = selection.startLineNumber === selection.endLineNumber
-  if (isSingleLineSelection) {
-    return null
-  }
-
-  if (endLine < startLine) {
-    return null
-  }
 
   const codeFenceLanguage = getCodeFenceLanguage(language)
   const codeBlock = selectedText.endsWith('\n') ? selectedText : `${selectedText}\n`
@@ -30,6 +25,13 @@ export function formatCopiedSelectionWithContext({
   return `File: ${relativePath}\n${lineLabel}\n\n\`\`\`${codeFenceLanguage}\n${codeBlock}\`\`\``
 }
 
+export function canCopySelectionWithContext(selection: IRange): boolean {
+  return (
+    selection.startLineNumber !== selection.endLineNumber &&
+    getInclusiveEndLine(selection) >= selection.startLineNumber
+  )
+}
+
 export function getContextualCopyLineRange(selection: IRange): {
   startLine: number
   endLine: number

src/renderer/src/components/editor/setup-contextual-copy.test.ts

@@ -29,6 +29,8 @@ vi.mock('@/lib/primary-selection', () => ({
   setPrimarySelectionText: () => {}
 }))
 
+vi.mock('./editor-shortcuts', () => ({ editorShortcutMatches: () => true }))
+
 describe('setupContextualCopy', () => {
   afterEach(() => {
     vi.unstubAllGlobals()
@@ -85,9 +87,16 @@ describe('setupContextualCopy', () => {
     expect(setInterval).not.toHaveBeenCalled()
   })
 
-  it('polls a focused editor while a contextual copy hint is visible', () => {
-    const setInterval = vi.fn(() => 1)
+  it('refreshes a visible hint without reading selection text and extracts it only on copy', async () => {
+    let refreshHint = (): void => {}
+    let keydown = (_event: KeyboardEvent): void => {}
+    const setInterval = vi.fn((callback: () => void) => {
+      refreshHint = callback
+      return 1
+    })
+    const writeClipboardText = vi.fn(async (_text: string) => {})
     vi.stubGlobal('window', {
+      api: { ui: { writeClipboardText } },
       clearInterval: vi.fn(),
       clearTimeout: vi.fn(),
       setInterval,
@@ -111,16 +120,24 @@ describe('setupContextualCopy', () => {
       getStartPosition: () => ({ lineNumber: 1, column: 1 }),
       getEndPosition: () => ({ lineNumber: 2, column: 4 })
     }
+    const selectedText = `${'x'.repeat(4 * 1024 * 1024)}\ntwo`
+    const getValueInRange = vi.fn(() => selectedText)
+    // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: The editor stub implements every method setupContextualCopy invokes in this scenario.
     const editorInstance = {
       addContentWidget: vi.fn(),
       getContainerDomNode: () => ({
-        addEventListener: vi.fn(),
-        removeEventListener: vi.fn()
+        addEventListener: (type: string, callback: (event: KeyboardEvent) => void) => {
+          if (type === 'keydown') {
+            keydown = callback
+          }
+        },
+        removeEventListener: vi.fn(),
+        getBoundingClientRect: () => ({ left: 0, top: 0, width: 500 })
       }),
       getLayoutInfo: () => ({ height: 500 }),
       getModel: () => ({
         getLineMaxColumn: () => 4,
-        getValueInRange: () => 'one\ntwo'
+        getValueInRange
       }),
       getScrolledVisiblePosition: () => ({ top: 20, left: 8, height: 16 }),
       getSelection: () => selection,
@@ -148,6 +165,20 @@ describe('setupContextualCopy', () => {
     })
 
     expect(setInterval).toHaveBeenCalledTimes(1)
+    for (let tick = 0; tick < 20; tick += 1) {
+      refreshHint()
+    }
+    expect(getValueInRange).not.toHaveBeenCalled()
+
+    // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: Shortcut matching is mocked; the handler reads only these event methods.
+    keydown({ preventDefault: vi.fn(), stopPropagation: vi.fn() } as unknown as KeyboardEvent)
+    await Promise.resolve()
+    expect(getValueInRange).toHaveBeenCalledTimes(1)
+    expect(writeClipboardText).toHaveBeenCalledWith(
+      `File: src/example.ts\nLines: 1-2\n\n\`\`\`ts\n${selectedText}\n\`\`\``
+    )
+    refreshHint()
+    expect(getValueInRange).toHaveBeenCalledTimes(1)
   })
 
   it('clears editor-scoped contextual copy cleanup on dispose', () => {

src/renderer/src/components/editor/setup-contextual-copy.ts

@@ -3,7 +3,11 @@ import { formatShortcutLabel } from '@/hooks/useShortcutLabel'
 import { monaco } from '@/lib/monaco-setup'
 import { useAppStore } from '@/store'
 import { editorShortcutMatches } from './editor-shortcuts'
-import { formatCopiedSelectionWithContext, getContextualCopyLineRange } from './selection-copy'
+import {
+  canCopySelectionWithContext,
+  formatCopiedSelectionWithContext,
+  getContextualCopyLineRange
+} from './selection-copy'
 import {
   PRIMARY_SELECTION_MAX_LENGTH,
   isPrimarySelectionEnabled,
@@ -87,8 +91,10 @@ export function setupContextualCopy({
 
   const updateCopyHint = (): void => {
     updateCopyHintLabel()
-    const contextualCopyText = getContextualCopyText()
-    if (!contextualCopyText) {
+    const model = editorInstance.getModel()
+    const selection = editorInstance.getSelection()
+    // Why: hint ticks need selection bounds; extracting the selected text scales with file size.
+    if (!model || !selection || selection.isEmpty() || !canCopySelectionWithContext(selection)) {
       copyHintNode.style.display = 'none'
       copyHintWidgetPosition = null
       editorInstance.layoutContentWidget(copyHintWidget)
@@ -102,15 +108,6 @@ export function setupContextualCopy({
       return
     }
 
-    const model = editorInstance.getModel()
-    const selection = editorInstance.getSelection()
-    if (!model || !selection) {
-      copyHintNode.style.display = 'none'
-      copyHintWidgetPosition = null
-      editorInstance.layoutContentWidget(copyHintWidget)
-      return
-    }
-
     const { startLine, endLine } = getContextualCopyLineRange(selection)
     const startVisiblePosition = editorInstance.getScrolledVisiblePosition(
       selection.getStartPosition()