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This adds support in Flight for serializing four kinds of streams: - `ReadableStream` with objects as a model. This is a single shot iterator so you can read it only once. It can contain any value including Server Components. Chunks are encoded as is so if you send in 10 typed arrays, you get the same typed arrays out on the other side. - Binary `ReadableStream` with `type: 'bytes'` option. This supports the BYOB protocol. In this mode, the receiving side just gets `Uint8Array`s and they can be split across any single byte boundary into arbitrary chunks. - `AsyncIterable` where the `AsyncIterator` function is different than the `AsyncIterable` itself. In this case we assume that this might be a multi-shot iterable and so we buffer its value and you can iterate it multiple times on the other side. We support the `return` value as a value in the single completion slot, but you can't pass values in `next()`. If you want single-shot, return the AsyncIterator instead. - `AsyncIterator`. These gets serialized as a single-shot as it's just an iterator. `AsyncIterable`/`AsyncIterator` yield Promises that are instrumented with our `.status`/`.value` convention so that they can be synchronously looped over if available. They are also lazily parsed upon read. We can't do this with `ReadableStream` because we use the native implementation of `ReadableStream` which owns the promises. The format is a leading row that indicates which type of stream it is. Then a new row with the same ID is emitted for every chunk. Followed by either an error or close row. `AsyncIterable`s can also be returned as children of Server Components and then they're conceptually the same as fragment arrays/iterables. They can't actually be used as children in Fizz/Fiber but there's a separate plan for that. Only `AsyncIterable` not `AsyncIterator` will be valid as children - just like sync `Iterable` is already supported but single-shot `Iterator` is not. Notably, neither of these streams represent updates over time to a value. They represent multiple values in a list. When the server stream is aborted we also close the underlying stream. However, closing a stream on the client, doesn't close the underlying stream. A couple of possible follow ups I'm not planning on doing right now: - [ ] Free memory by releasing the buffer if an Iterator has been exhausted. Single shots could be optimized further to release individual items as you go. - [ ] We could clean up the underlying stream if the only pending data that's still flowing is from streams and all the streams have cleaned up. It's not very reliable though. It's better to do cancellation for the whole stream - e.g. at the framework level. - [ ] Implement smarter Binary Stream chunk handling. Currently we wait until we've received a whole row for binary chunks and copy them into consecutive memory. We need this to preserve semantics when passing typed arrays. However, for binary streams we don't need that. We can just send whatever pieces we have so far. |
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| .. | ||
| __tests__ | ||
| codes.json | ||
| extract-errors.js | ||
| invertObject.js | ||
| README.md | ||
| transform-error-messages.js | ||
| Types.js | ||
The error code system substitutes React's error messages with error IDs to provide a better debugging support in production. Check out the blog post here.
codes.jsoncontains the mapping from IDs to error messages. This file is generated by the Gulp plugin and is used by both the Babel plugin and the error decoder page in our documentation. This file is append-only, which means an existing code in the file will never be changed/removed.extract-errors.jsis an node script that traverses our codebase and updatescodes.json. You can test it by runningyarn extract-errors. It works by crawling the build artifacts directory, so you need to have either run the build script or downloaded pre-built artifacts (e.g. withyarn download build). It works with partial builds, too.transform-error-messagesis a Babel pass that rewrites error messages to IDs for a production (minified) build.