Summary:
This shows progress for the download of the JS bundle (different from the packager transform progress that we show already). This is useful especially when loading the JS bundle from a remote source or when developing on device (on simulator + localhost it pretty much just downloads instantly). This will be nice for the expo client since all bundles are loaded over the network and can take several seconds to load.
This depends on https://github.com/facebook/metro-bundler/pull/28 to work but won't crash or anything without it, it just won't show the progress percentage.
**Test plan**
Tested that bundle download progress is shown properly in RNTester on both localhost + simulator and on real device with network conditionner to simulate a slow loading bundle.
Tested that it doesn't cause issues if the packager doesn't send the Content-Length header.
Closes https://github.com/facebook/react-native/pull/15066
Differential Revision: D5449073
Pulled By: shergin
fbshipit-source-id: 43a8fb559393bbdc04f77916500e21898695bac5
Summary:
Packager can take a long time to load and the progress is usually displayed in another window (Terminal). I'm adding support for showing a UI inside React Native app for packager's progress when loading a bundle.
This is how it will work:
1. React Native sends request to packager with `Accept: multipart/mixed` header.
2. Packager will detect that header to detect that client supports progress events and will reply with `Content-Type: multipart/mixed`.
3. While building the bundle it will emit chunks with small metadata (like `{progress: 0.3}`). In the end it will send the last chunk with the content of the bundle.
4. RN runtime will be receiving the events, for each progress event it will update the UI. The last chunk will be the actual bundle which will end the download process.
This workflow is totally backwards-compatible -- normally RN doesn't set the `Accept` header.
Reviewed By: mmmulani
Differential Revision: D3845684
fbshipit-source-id: 5b3d2c5a4c6f4718d7e5de060d98f17491e82aba
Janic Duplessis
Alex Kotliarskyi
