Merge pull request #67 from y574444354/fix/tab-protection-measured-text

fix: protect tabs from wrap-ansi expansion in MeasuredText

src/utils/Cursor.ts

@@ -1290,11 +1290,30 @@ export class MeasuredText {
   }
 
   private measureWrappedText(): WrappedLine[] {
-    const wrappedText = wrapAnsi(this.text, this.columns, {
+    // Protect tabs from being expanded by npm wrap-ansi in Node.js dist builds.
+    // Bun.wrapAnsi preserves tabs, but npm wrap-ansi expands them to spaces,
+    // which breaks the indexOf-based offset recovery below.
+    const TAB_PLACEHOLDER_CANDIDATES = ['\u2060', '\u2061', '\u2062', '\u2063']
+    const tabPlaceholder = TAB_PLACEHOLDER_CANDIDATES.find(
+      (ch) => !this.text.includes(ch),
+    )
+    const hasTabs = this.text.includes('\t')
+
+    const textForWrap =
+      hasTabs && tabPlaceholder
+        ? this.text.replaceAll('\t', tabPlaceholder)
+        : this.text
+
+    const wrappedTextRaw = wrapAnsi(textForWrap, this.columns, {
       hard: true,
       trim: false,
     })
 
+    const wrappedText =
+      hasTabs && tabPlaceholder
+        ? wrappedTextRaw.replaceAll(tabPlaceholder, '\t')
+        : wrappedTextRaw
+
     const wrappedLines: WrappedLine[] = []
     let searchOffset = 0
     let lastNewLinePos = -1

src/utils/__tests__/Cursor.test.ts

@@ -0,0 +1,89 @@
+import { describe, test, expect } from 'bun:test'
+import { Cursor } from '../Cursor'
+
+describe('MeasuredText tab protection', () => {
+  test('Cursor.fromText with tabs does not throw', () => {
+    const cursor = Cursor.fromText('a\tb', 80)
+    expect(cursor).toBeTruthy()
+    expect(cursor.text).toBe('a\tb')
+  })
+
+  test('tab text preserves original tabs after measurement', () => {
+    const cursor = Cursor.fromText('hello\tworld', 80)
+    expect(cursor.text).toBe('hello\tworld')
+    // Trigger measurement
+    cursor.getPosition()
+    expect(cursor.text).toBe('hello\tworld')
+  })
+
+  test('multi-line tab text works', () => {
+    const cursor = Cursor.fromText('foo\n\tbar', 80)
+    expect(cursor.text).toBe('foo\n\tbar')
+    expect(() => cursor.getPosition()).not.toThrow()
+  })
+
+  test('tabs in narrow columns (triggering visual wrap) does not throw', () => {
+    // 10 cols is narrow enough that tabs + text will wrap
+    const cursor = Cursor.fromText('x\t\thello world\tfoo', 10)
+    expect(() => cursor.getPosition()).not.toThrow()
+    expect(cursor.text).toBe('x\t\thello world\tfoo')
+  })
+
+  test('getPosition returns valid coordinates for tab text', () => {
+    const cursor = Cursor.fromText('a\tb\tc', 80)
+    const pos = cursor.getPosition()
+    expect(pos.line).toBeGreaterThanOrEqual(0)
+    expect(pos.column).toBeGreaterThanOrEqual(0)
+  })
+
+  test('cursor movement on tab text does not throw', () => {
+    const cursor = Cursor.fromText('abc\tdef\tghi', 80)
+    // Move right through tab
+    const right1 = cursor.right()
+    expect(() => right1.getPosition()).not.toThrow()
+    const right2 = right1.right()
+    expect(() => right2.getPosition()).not.toThrow()
+    // Move to end
+    const end = cursor.endOfFile()
+    expect(() => end.getPosition()).not.toThrow()
+    // Move back
+    expect(() => end.left().getPosition()).not.toThrow()
+  })
+
+  test('tab text in very narrow views (1 col) does not throw', () => {
+    const cursor = Cursor.fromText('a\tb', 1)
+    expect(() => cursor.getPosition()).not.toThrow()
+  })
+
+  test('text with only tabs does not throw', () => {
+    const cursor = Cursor.fromText('\t\t', 80)
+    expect(() => cursor.getPosition()).not.toThrow()
+    expect(cursor.text).toBe('\t\t')
+  })
+
+  test('mixed tabs and newlines', () => {
+    const cursor = Cursor.fromText('a\tb\nc\td\ne\tf', 80)
+    expect(() => cursor.getPosition()).not.toThrow()
+    // Move to last line
+    const eof = cursor.endOfFile()
+    expect(eof.text).toBe('a\tb\nc\td\ne\tf')
+  })
+
+  test('placeholder characters in text are handled gracefully', () => {
+    // Text already contains \u2060 (word joiner)
+    const textWithPlaceholder = 'ab\u2060\tc'
+    const cursor = Cursor.fromText(textWithPlaceholder, 80)
+    expect(() => cursor.getPosition()).not.toThrow()
+    expect(cursor.text).toBe(textWithPlaceholder)
+  })
+
+  test('text with all placeholder candidates still works', () => {
+    // Text contains all four zero-width placeholder candidates
+    const allPlaceholders = 'a\u2060\u2061\u2062\u2063\tb'
+    const cursor = Cursor.fromText(allPlaceholders, 80)
+    expect(() => cursor.getPosition()).not.toThrow()
+    expect(cursor.text).toBe(allPlaceholders)
+  })
+})
+
+