fixing lines overlapping

test/deleted-lines.test.tsx

@@ -0,0 +1,71 @@
+// @vitest-environment jsdom
+//
+// A removed line owns no line in Actual, so it cannot carry a band. It leaves a
+// rule on the edge of the line that took its place instead. The mock project has
+// no such change, so this drives the renderer with a git payload of its own.
+import { afterEach, beforeAll, beforeEach, describe, expect, it, vi } from 'vitest'
+import { cleanup, fireEvent, render, waitFor } from '@testing-library/react'
+import React from 'react'
+
+vi.mock('../src/renderer/src/terminals', () => {
+  let n = 0
+  return { Terminal: () => null, lid: () => ++n }
+})
+
+import { App } from '../src/renderer/src/App'
+import { ProjectProvider } from '../src/renderer/src/project'
+import { installBridge, removeBridge } from './stub-bridge'
+
+const HEAD = 'keep\ngone\ntail\n'
+const DISK = 'keep\ntail\n'
+
+beforeAll(() => {
+  globalThis.ResizeObserver = class { observe(): void {} unobserve(): void {} disconnect(): void {} } as never
+  if (!Element.prototype.scrollIntoView) Element.prototype.scrollIntoView = (): void => {}
+})
+beforeEach(() => {
+  installBridge([{ path: 'demo.txt', status: 'M', staged: false, original: HEAD, updated: DISK }], { 'demo.txt': DISK })
+})
+afterEach(() => {
+  cleanup()
+  localStorage.clear()
+  removeBridge()
+})
+
+async function openRow(): Promise<HTMLElement> {
+  const c = render(<ProjectProvider><App /></ProjectProvider>).container
+  const row = await waitFor(() => {
+    const r = c.querySelector<HTMLElement>('.git-row')
+    if (!r) throw new Error('git not ready')
+    return r
+  })
+  fireEvent.click(row)
+  await waitFor(() => expect(c.querySelector('.code-edit')).toBeTruthy())
+  return c
+}
+
+describe('a change that only removes a line', () => {
+  it('rules the edge of the line below it, and tints nothing', async () => {
+    const c = await openRow()
+    await waitFor(() => expect(c.querySelectorAll('.ce-gaprule')).toHaveLength(1))
+    expect(c.querySelector('.ce-band')).toBeNull()
+    expect(c.querySelector('.ce-gutter .chg')).toBeNull()
+  })
+
+  it('hands the removed line to the hover panel', async () => {
+    const c = await openRow()
+    const scroll = await waitFor(() => {
+      const el = c.querySelector<HTMLElement>('.ce-scroll')
+      if (!el || !c.querySelector('.ce-gaprule')) throw new Error('rule not ready')
+      return el
+    })
+    // 'tail' took the place of the removed line, and sits on line 2.
+    fireEvent.mouseMove(scroll, { clientY: 10 + 20 + 5 })
+    const peek = await waitFor(() => {
+      const p = c.querySelector<HTMLElement>('.peek')
+      if (!p) throw new Error('peek not ready')
+      return p
+    })
+    expect(Array.from(peek.querySelectorAll('.ln-row.del')).map((el) => el.textContent?.replace(/^\d+/, ''))).toEqual(['gone'])
+  })
+})