Fix pagination (#11448)

Co-authored-by: Eric Bailey <git@esb.lol>

src/state/queries/util.test.tsx

@@ -0,0 +1,100 @@
+import {renderHook} from '@testing-library/react-native'
+
+import {useAutoPagination} from './util'
+
+function query(overrides: Record<string, unknown> = {}) {
+  return {
+    data: {pageParams: [undefined]},
+    isLoading: false,
+    isRefetching: false,
+    isFetchingNextPage: false,
+    hasNextPage: true,
+    fetchNextPage: jest.fn().mockResolvedValue(undefined),
+    ...overrides,
+  }
+}
+
+describe('useAutoPagination', () => {
+  it('fetches another page when visible items are missing', () => {
+    const value = query()
+
+    renderHook(() => useAutoPagination(value, 0, 10))
+
+    expect(value.fetchNextPage).toHaveBeenCalledTimes(1)
+  })
+
+  it('stops when the requested number of items is visible', () => {
+    const value = query()
+
+    renderHook(() => useAutoPagination(value, 10, 10))
+
+    expect(value.fetchNextPage).not.toHaveBeenCalled()
+  })
+
+  it('stops when the server repeats a cursor', () => {
+    const value = query({data: {pageParams: [undefined, 'a', 'a']}})
+
+    renderHook(() => useAutoPagination(value, 0, 10))
+
+    expect(value.fetchNextPage).not.toHaveBeenCalled()
+  })
+
+  it('stops when structured page params repeat a cursor', () => {
+    const value = query({
+      data: {pageParams: [undefined, {cursor: 'a'}, {cursor: 'a'}]},
+    })
+
+    renderHook(() => useAutoPagination(value, 0, 10))
+
+    expect(value.fetchNextPage).not.toHaveBeenCalled()
+  })
+
+  it('stops when a cursor repeats non-adjacently', () => {
+    const value = query({data: {pageParams: [undefined, 'a', 'b', 'a']}})
+
+    renderHook(() => useAutoPagination(value, 0, 10))
+
+    expect(value.fetchNextPage).not.toHaveBeenCalled()
+  })
+
+  it('fills one page after switching to a smaller cached query', () => {
+    const first = query({hasNextPage: false})
+    const second = query()
+    let value = first
+    let itemCount = 10
+    const {rerender} = renderHook(() => useAutoPagination(value, itemCount, 10))
+
+    value = second
+    itemCount = 5
+    rerender(undefined)
+
+    expect(second.fetchNextPage).toHaveBeenCalledTimes(1)
+  })
+
+  it('resets the attempt limit after switching to cached data with the same item count', () => {
+    const fetchNextPage = jest.fn().mockResolvedValue(undefined)
+    const data = {pageParams: [undefined]}
+    let value = query({fetchNextPage, data})
+    const itemCount = 0
+    const {rerender} = renderHook(() => useAutoPagination(value, itemCount, 10))
+
+    for (let i = 1; i < 50; i++) {
+      value = query({
+        fetchNextPage,
+        data,
+      })
+      rerender(undefined)
+    }
+    expect(fetchNextPage).toHaveBeenCalledTimes(49)
+
+    const second = query({
+      data: {
+        pageParams: Array.from({length: 51}, (_, i) => `new-cursor-${i}`),
+      },
+    })
+    value = second
+    rerender(undefined)
+
+    expect(second.fetchNextPage).toHaveBeenCalledTimes(1)
+  })
+})