When Float was first developed the internal implementation and external
interface were the same. This is problematic for a few reasons. One, the
public interface is typed but it is also untrusted and we should not
assume that it is actually respected. Two, the internal implementations
can get called from places other than the the public interface and
having to construct an options argument that ends up being destructured
to process the request is computationally wasteful and may limit JIT
optimizations to some degree. Lastly, the wire format was not as
compressed as it could be and it was untyped.
This refactor aims to address that by separating the public interface
from the internal implementations so we can solve these challenges and
also make it easier to change Float in the future
* The internal dispatcher method preinit is now preinitStyle and
preinitScript.
* The internal dispatcher method preinitModule is now
preinitModuleScript in anticipation of different implementations for
other module types in the future.
* The wire format is explicitly typed and only includes options if they
are actually used omitting undefined and nulls.
* Some function arguments are not options even if they are optional. For
instance precedence can be null/undefined because we deafult it to
'default' however we don't cosnider this an option because it is not
something we transparently apply as props to the underlying instance.
* Fixes a problem with keying images in flight where srcset and sizes
were not being taken into account.
* Moves argument validation into the ReactDOMFloat file where it is
shared with all runtimes that expose these methods
* Fixes crossOrigin serialization to use empty string except when
'use-credentials'
stacked on #27222
When I initially developed Float I was trying to be extremely clever in
how to explain when there are mismatching Resource instances. I still
think that we should do some kind of validation here but I want to
implement something much simpler. In practice there are not many cases
where you would accidentally create the same resource twice but with
differing props. Since I am going to land `preloadModule` and
`preinitModule` soon and I want to avoid adding to the overly complex
dev validation there I am going to remove it now and add something later
that is simplified.
For float methods the href argument is usually all we need to uniquely
key the request. However when preloading responsive images it is
possible that you may need more than one preload for differing
imagesizes attributes. When using imagesrcset for preloads the href
attribute acts more like a fallback href. For keying purposes the
imagesrcset becomes the primary key conceptually.
This change updates the keying logic for `ReactDOM.preload()` when you
pass `{as: "image"}`
1. If `options.imageSrcSet` is a non-emtpy string the key is defined as
`options.imageSrcSet + options.imageSizes`. The `href` argument is still
required but does not participate in keying.
2. If `options.imageSrcSet` is empty, missing, or an invalid format the
key is defined as the `href`. Changing the `options.imageSizes` does not
affect the key as this option is inert when not using
`options.imageSrcSet`
Additionally, currently there is a bug in webkit (Safari) that causes
preload links to fail to use imageSrcSet and fallback to href even when
the browser will correctly resolve srcset on an `<img>` tag. Because the
drawbacks of preloading the wrong image (href over imagesrcset) in a
modern browser outweight the drawbacks of not preloading anything for
responsive images in browsers that do not support srcset at all we will
omit the `href` attribute whenever `options.imageSrcSet` is provided. We
still require you provide an href since we want to be able to revert
this behavior once all major browsers support it
bug link: https://bugs.webkit.org/show_bug.cgi?id=231150
## Hoistables
In the original implementation of Float, all hoisted elements were
treated like Resources. They had deduplication semantics and hydrated
based on a key. This made certain kinds of hoists very challenging such
as sequences of meta tags for `og:image:...` metadata. The reason is
each tag along is not dedupable based on only it's intrinsic properties.
two identical tags may need to be included and hoisted together with
preceding meta tags that describe a semantic object with a linear set of
html nodes.
It was clear that the concept of Browser Resources (stylesheets /
scripts / preloads) did not extend universally to all hositable tags
(title, meta, other links, etc...)
Additionally while Resources benefit from deduping they suffer an
inability to update because while we may have multiple rendered elements
that refer to a single Resource it isn't unambiguous which element owns
the props on the underlying resource. We could try merging props, but
that is still really hard to reason about for authors. Instead we
restrict Resource semantics to freezing the props at the time the
Resource is first constructed and warn if you attempt to render the same
Resource with different props via another rendered element or by
updating an existing element for that Resource.
This lack of updating restriction is however way more extreme than
necessary for instances that get hoisted but otherwise do not dedupe;
where there is a well defined DOM instance for each rendered element. We
should be able to update props on these instances.
Hoistable is a generalization of what Float tries to model for hoisting.
Instead of assuming every hoistable element is a Resource we now have
two distinct categories, hoistable elements and hoistable resources. As
one might guess the former has semantics that match regular Host
Components except the placement of the node is usually in the <head>.
The latter continues to behave how the original implementation of
HostResource behaved with the first iteration of Float
### Hoistable Element
On the server hoistable elements render just like regular tags except
the output is stored in special queues that can be emitted in the stream
earlier than they otherwise would be if rendered in place. This also
allow for instance the ability to render a hoistable before even
rendering the <html> tag because the queues for hoistable elements won't
flush until after we have flushed the preamble (`<DOCTYPE
html><html><head>`).
On the client, hoistable elements largely operate like HostComponents.
The most notable difference is in the hydration strategy. If we are
hydrating and encounter a hoistable element we will look for all tags in
the document that could potentially be a match and we check whether the
attributes match the props for this particular instance. We also do this
in the commit phase rather than the render phase. The reason hydration
can be done for HostComponents in render is the instance will be removed
from the document if hydration fails so mutating it in render is safe.
For hoistables the nodes are not in a hydration boundary (Root or
SuspenseBoundary at time of writing) and thus if hydration fails and we
may have an instance marked as bound to some Fiber when that Fiber never
commits. Moving the hydration matching to commit ensures we will always
succeed in pairing the hoisted DOM instance with a Fiber that has
committed.
### Hoistable Resource
On the server and client the semantics of Resources are largely the same
they just don't apply to title, meta, and most link tags anymore.
Resources hoist and dedupe via an `href` key and are ref counted. In a
future update we will add a garbage collector so we can clean up
Resources that no longer have any references
## `<style>` support
In earlier implementations there was no support for <style> tags. This
PR adds support for treating `<style href="..."
precedence="...">...</style>` as a Resource analagous to `<link
rel="stylesheet" href="..." precedence="..." />`
It may seem odd at first to require an href to get Resource semantics
for a style tag. The rationale is that these are for inlining of actual
external stylesheets as an optimization and for URI like scoping of
inline styles for css-in-js libraries. The href indicates that the key
space for `<style>` and `<link rel="stylesheet" />` Resources is shared.
and the precedence is there to allow for interleaving of both kinds of
Style resources. This is an advanced feature that we do not expect most
app developers to use directly but will be quite handy for various
styling libraries and for folks who want to inline as much as possible
once Fizz supports this feature.
## refactor notes
* HostResource Fiber type is renamed HostHoistable to reflect the
generalization of the concept
* The Resource object representation is modified to reduce hidden class
checks and to use less memory overall
* The thing that distinguishes a resource from an element is whether the
Fiber has a memoizedState. If it does, it will use resource semantics,
otherwise element semantics
* The time complexity of matching hositable elements for hydration
should be improved
This enables the "exact_empty_objects" setting for Flow which makes
empty objects exact instead of building up the type as properties are
added in code below. This is in preparation to Flow 191 which makes this
the default and removes the config.
More about the change in the Flow blog
[here](https://medium.com/flow-type/improved-handling-of-the-empty-object-in-flow-ead91887e40c).
stacked on https://github.com/facebook/react/pull/25514
This PR adds support for any type of Link as long as it has a string rel
and href and does not include an onLoad or onError property.
The semantics for generic link resources matches other head resources,
they will be inserted and removed as their ref counts go positive and
back to zero.
Keys are based on rel, href, sizes, and media.
on the server preconnect and prefetch-dns are privileged and will emit
near the start of the stream.
* Facebook -> Meta in copyright
rg --files | xargs sed -i 's#Copyright (c) Facebook, Inc. and its affiliates.#Copyright (c) Meta Platforms, Inc. and affiliates.#g'
* Manual tweaks
* float enhance!!!
Support preinit as script
Support resources from async scripts
Support saving the precedence place when rendering the shell
There was a significant change to the flushing order of resources which follows the general principal of...
1. stuff that blocks display
2. stuff that we know will be used
3. stuff that was explicitly preloaded
As a consequence if you preinit a style now it won't automatically flush in the shell unless you actually depend on it in your tree. To avoid races with precedence order we now emit a tag that saves the place amongst the precedence hierarchy so late insertions still end up where they were intended
There is also a novel hydration pathway for certain tags. If you render an async script with an onLoad or onError it will always treat it like an insertion rather than a hydration.
* restore preinit style flushing behavior and nits
* [Fizz/Float] Float for stylesheet resources
This commit implements Float in Fizz and on the Client. The initial set of supported APIs is roughly
1. Convert certain stylesheets into style Resources when opting in with precedence prop
2. Emit preloads for stylesheets and explicit preload tags
3. Dedupe all Resources by href
4. Implement ReactDOM.preload() to allow for imperative preloading
5. Implement ReactDOM.preinit() to allow for imperative preinitialization
Currently supports
1. style Resources (link rel "stylesheet")
2. font Resources (preload as "font")
later updates will include support for scripts and modules
Jan KassensandGitHub
Josh StoryandGitHub
Andrew ClarkandGitHub