We already support these in the sense that they're Iterable so they just
get serialized as arrays. However, these are part of the Structured
Clone algorithm [and should be
supported](https://github.com/facebook/react/issues/25687).
The encoding is simply the same form as the Iterable, which is
conveniently the same as the constructor argument. The difference is
that now there's a separate reference to it.
It's a bit awkward because for multiple reference to the same value,
it'd be a new Map/Set instance for each reference. So to encode sharing,
it needs one level of indirection with its own ID. That's not really a
big deal for other types since they're inline anyway - but since this
needs to be outlined it creates possibly two ids where there only needs
to be one or zero.
One variant would be to encode this in the row type. Another variant
would be something like what we do for React Elements where they're
arrays but tagged with a symbol. For simplicity I stick with the simple
outlining for now.
Use the Blob constructor + append with filename instead of File
constructor. Node.js doesn't expose a global File constructor but does
support it in this form.
Queue fields until we get the 'end' event from the previous file. We
rely on previous files being available by the time a field is resolved.
However, since the 'end' event in Readable is fired after two
micro-tasks, these are not resolved in order.
I use a queue of the fields while we're still waiting on files to
finish. This still doesn't resolve files and fields in order relative to
each other but that doesn't matter for our usage.
- substr is Annex B
- substring silently flips its arguments if they're in the "wrong order", which is confusing
- slice is better than sliced bread (no pun intended) and also it works the same way on Arrays so there's less to remember
---
> I'd be down to just lint and enforce a single form just for the potential compression savings by using a repeated string.
_Originally posted by @sebmarkbage in https://github.com/facebook/react/pull/26663#discussion_r1170455401_
Builds on top of https://github.com/facebook/react/pull/26661
This lets you pass FormData objects through the Flight Reply
serialization. It does that by prefixing each entry with the ID of the
reference and then the decoding side creates a new FormData object
containing only those fields (without the prefix).
Ideally this should be more generic. E.g. you should be able to pass
Blobs, Streams and Typed Arrays by reference inside plain objects too.
You should also be able to send Blobs and FormData in the regular Flight
serialization too so that they can go both directions. They should be
symmetrical. We'll get around to adding more of those features in the
Flight protocol as we go.
---------
Co-authored-by: Sophie Alpert <git@sophiebits.com>
Added an explicit type to all $FlowFixMe suppressions to reduce
over-suppressions of new errors that might be caused on the same lines.
Also removes suppressions that aren't used (e.g. in a `@noflow` file as
they're purely misleading)
Test Plan:
yarn flow-ci
This adds `encodeReply` to the Flight Client and `decodeReply` to the
Flight Server.
Basically, it's a reverse Flight. It serializes values passed from the
client to the server. I call this a "Reply". The tradeoffs and
implementation details are a bit different so it requires its own
implementation but is basically a clone of the Flight Server/Client but
in reverse. Either through callServer or ServerContext.
The goal of this project is to provide the equivalent serialization as
passing props through RSC to client. Except React Elements and
Components and such. So that you can pass a value to the client and back
and it should have the same serialization constraints so when we add
features in one direction we should mostly add it in the other.
Browser support for streaming request bodies are currently very limited
in that only Chrome supports it. So this doesn't produce a
ReadableStream. Instead `encodeReply` produces either a JSON string or
FormData. It uses a JSON string if it's a simple enough payload. For
advanced features it uses FormData. This will also let the browser
stream things like File objects (even though they're not yet supported
since it follows the same rules as the other Flight).
On the server side, you can either consume this by blocking on
generating a FormData object or you can stream in the
`multipart/form-data`. Even if the client isn't streaming data, the
network does. On Node.js busboy seems to be the canonical library for
this, so I exposed a `decodeReplyFromBusboy` in the Node build. However,
if there's ever a web-standard way to stream form data, or if a library
wins in that space we can support it. We can also just build a multipart
parser that takes a ReadableStream built-in.
On the server, server references passed as arguments are loaded from
Node or Webpack just like the client or SSR does. This means that you
can create higher order functions on the client or server. This can be
tokenized when done from a server components but this is a security
implication as it might be tempting to think that these are not fungible
but you can swap one function for another on the client. So you have to
basically treat an incoming argument as insecure, even if it's a
function.
I'm not too happy with the naming parity:
Encode `server.renderToReadableStream` Decode: `client.createFromFetch`
Decode `client.encodeReply` Decode: `server.decodeReply`
This is mainly an implementation details of frameworks but it's annoying
nonetheless. This comes from that `renderToReadableStream` does do some
"rendering" by unwrapping server components etc. The `create` part comes
from the parity with Fizz/Fiber where you `render` on the server and
`create` a root on the client.
Open to bike-shedding this some more.
---------
Co-authored-by: Josh Story <josh.c.story@gmail.com>
Sebastian Markbåge
Sophie Alpert
Josh Story
Sebastian Silbermann
Jan Kassens