react-native/Libraries/Lists/__tests__
Louis Lagrange 264d67c424 Add ListEmptyComponent prop
Summary:
Hey there :)

Please let me know if the name `ListEmptyComponent` should be changed. I also thought about `ListNoItemsComponent`. Or maybe `ListPlaceholderComponent`?

- [x] Explain the **motivation** for making this change.
- [x] Provide a **test plan** demonstrating that the code is solid.
- [x] Match the **code formatting** of the rest of the codebase.
- [x] Target the `master` branch, NOT a "stable" branch.

In a FlatList, I wanted to show some placeholder when my data is empty (while keeping eventual Header/Footer/RefreshControl).
A way around this issue would be to do something like adding a `ListHeaderComponent` that checks if the list is empty, like so:
```js
ListHeaderComponent={() => (!data.length ? <Text style={styles.noDataText}>No data found</Text> : null)}
```
But I felt it was not easily readable as soon as you have an actual header.

This PR adds a `ListEmptyComponent` that is rendered when the list is empty.

I added tests for VirtualizedList, FlatList and SectionList and ran `yarn test -- -u`. I then checked that the snapshots changed like I wanted.
I also tested this against one of my project, though I had to manually add my changes because the project is on RN 0.43.

Here are the docs screenshots:
- [VirtualizedList](https://cloud.githubusercontent.com/assets/82368/25566000/0ebf2b82-2dd2-11e7-8b80-d8c505f1f2d6.png)
- [FlatList](https://cloud.githubusercontent.com/assets/82368/25566005/2842ab42-2dd2-11e7-81b4-32c74c2b4fc3.png)
- [SectionList](https://cloud.githubusercontent.com/assets/82368/25566010/368aec1e-2dd2-11e7-9425-3bb5e5803513.png)

Thanks for your work!
Closes https://github.com/facebook/react-native/pull/13718

Differential Revision: D4993711

Pulled By: sahrens

fbshipit-source-id: 055b40f709067071e40308bdf5a37cedaa223dc5
2017-05-04 00:16:25 -07:00
..
__snapshots__ Add ListEmptyComponent prop 2017-05-04 00:16:25 -07:00
FillRateHelper-test.js Many improvements 2017-04-25 14:50:14 -07:00
FlatList-test.js Add ListEmptyComponent prop 2017-05-04 00:16:25 -07:00
SectionList-test.js Add ListEmptyComponent prop 2017-05-04 00:16:25 -07:00
ViewabilityHelper-test.js Re-License Lists with standard React Native License 2017-03-24 14:31:19 -07:00
VirtualizeUtils-test.js Re-License Lists with standard React Native License 2017-03-24 14:31:19 -07:00
VirtualizedList-test.js Add ListEmptyComponent prop 2017-05-04 00:16:25 -07:00