This release like the last is focusing on small quality of life improvements and adjustments that will help us move towards 2.0. So while not the most exciting release to everyone it provides some really important features and fixes to some developers. And unlike many previous releases the vast majority of the work and features came from PRs from the community. So really all I can say is Looks Good to Me! ## Better JSX Validation While still incomplete across templates we've added JSDOM to the compiler to better detect invalid HTML at build time by comparing what we expect the template to be with what a browser would output. This now includes things that are nested we didn't detect before like putting `<a>` inside other `<a>` tags which will lead to the browser "correcting" it in less than intuitive ways. ## Improved Exports While each environment in `solid-js/web` has its own methods to be used in the compiler. We are now exporting the client methods from the server to prevent weird import errors. Now these methods will throw if used in this environment but shouldn't break your build. Additionally we have seen some issues in bundlers that incorrectly feed our ESM exports back through the browser field. While this is a known issue they all pointed issues at each other and with no intention of fixing it. We have removed the browser field in this release, meaning some legacy packages may have issues resolving browser if they don't support export conditions. This is regretful but this blocked deployments on several platforms and since this was the only fix at our disposal after two years of attempting to push this issue to the bundlers to no avail, we've moved forward with it. ## Custom Element improvements We have a few improvements to our custom element support in this release. First off we now detect elements with the `is` attribute as custom elements which means all the special behavior is afforded to them. We've also improved our event handler delegating retargetting to better handle shadow DOM events. There were cases where we skipped over part of the tree. Finally we've added the `bool:` attribute namespace to handle explicitly setting certain attributes according to boolean attribute rules. While this isn't necessary for built-in booleans currently we handle most attributes as properties and we lacked a specific override. But now we have it: ```js <my-element bool:enable={isEnabled()}></my-element> ``` ## Support for handleEvent Syntax in Non-Delegated Events A little known thing is that events actually also support objects instead of functions (See: https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener) We(thanks @titoBouzout) realized we can use this mechanism as a way to set advanced rules like `passive` or `capture` on this object as way to handle all current and future event attributes that browsers might add. This way we don't need specific mechanisms like `oncapture:` (which is now deprecated). Instead using `on:` you can set the event properties you wish. ```js <> <div on:click={{ handleEvent(e) { console.log("clicked", e) }, once:true }/> <div on:wheel={{ handleEvent(e) { e.preventDefault() // only works on not passive events e.stopPropagation() console.log("wheel stopped?") }, passive: false }} /> </> ``` ## Other Updates We've fixed an issue with lazy images. Apparently, cloneNode doesn't handle them properly so we've updated our heuristic to treat templates with lazy images to be handled with `importNode`. We've improved our Hydration Mismatch Error to output the template of that it can't find the matching ID for. This should make it easier to track down where the hydration errors are occurring. There have been several hydration improvements over the later 1.8 releases so upgrading will likely improve the situation for those who have been facing issues. Finally, we've improved some of the types in the JSX and Signal Setter in this release. ------------- Big thanks to those who contributed to this release: @wkelly17, @olivercoad, @titoBouzout, @trusktr, @Huliiiiii. And thanks to all of you who gave feedback on the [Metadata/Head Tag RFC](https://github.com/solidjs/solid/discussions/2294). While it didn't make it in this time around you've definitely given us stuff to consider for its future design. Best, @ryansolid

> In Norse mythology, Bifröst (/ˈbɪvrɒst/), is a burning rainbow bridge that reaches between Midgard (Earth) and Asgard, the realm of the gods. I am first to admit this is not the most exciting release from a feature standpoint. I was looking for cool code snippets but these changes are for the most part all under the hood. We are in that time period between the end of 1.x and the start of 2.0. We recently made our new reactive experiments public and continue to build those out in public with [@solidjs/signals](https://github.com/solidjs/signals). We need to build for the future while bridging the gap with the present. This version is about addressing some of the fundamentals that will help projects like SolidStart move forward while we do the transition. Async and Resources need work and are too all in. It is great to have a solution but now that we have a better understanding we need to start breaking things apart into their fundamental pieces and exposing them in ways we can better leverage. And in Solid 1.8 a big part of that is rethinking serialization, our bridge between the server and the client. A lot of our learning here has come from applying what we have learned when doing performance benchmarks for the work that has been funded by [Google Chrome Aurora](https://www.solidjs.com/blog/chrome-supports-solidjs). In order to realize our goal we've had to update the foundations. ## De-duping Streaming Serialization This is the marquee feature of this release and is largely the work of @lxsmnsyc. Solid has been able to serialize promises and do streaming for a couple of years now, but it was very special-cased. Now it is a generic mechanism. This matters because it means that we have decoupled the promise serialization from Resources, and in so decoupled the whole "when the stream is done" from them. This opens up things like nested promises and being able to serialize more complicated data structures. We now also have a mechanism now that deeply de-dupes data serialized across flushes. If the data is ever serialized during the request we won't send it again even if sent in different streaming chunks. This is important for features like Islands where you might pass the same props to multiple Islands across different Suspense boundaries and don't want to send the data more than once. This is very beneficial where that data can be accessed at varying depths (recursive comments in say a Hackernews site) or other recursive data structures. ## Hydration Improvements Fragments for Hydration have been a bit of a pain and we keep seeming to have different issues reported around element duplication. Most commonly this has been around where there are `lazy` component siblings or where the fragment is top-level. After looking into and fixing an [issue for Astro](https://github.com/withastro/astro/pull/8365) I decided to look at some of the oldest bugs in Solid and found it was a similar bug. In many cases, the DOM can change throughout Hydration while doing things like streaming but we need to pause and resume hydration because code isn't available yet. While we don't create elements during hydration, getting an accurate snapshot of the DOM for the current state for future list reconciliation is a process we've had a few tries at but in 1.8 we update this in a way that makes sure it doesn't get out of date. Also in 1.8, we have added some performance improvements to hydration in the form of not redundantly setting attributes or props as the page hydrates similar to how we don't update text. This is all migration towards a future where we don't need to do as much hydration, but it is important to note that values will be kept as they were on the server rather than how they may compute at runtime during hydration. ## Smaller Templates In 1.7 we removed unnecessary closing tags from template strings. It was a bit painful because we were a bit overzealous at first. While I believe in the end we got to a good place, ultimately all but the simplest reductions have been hidden behind a compiler flag(`omitNestedClosingTags`). Thanks to work from @intrnl we are implementing another template size reduction technique of removing unnecessary quotes. Quotes are actually not required by HTML in some cases and it can add up. ## Other ### Fix NGINX Server Side Includes Comments led with `#` are treated as special directives for a few different servers so we've needed to change our open hydration markers to `$`. As usual, your version of Solid and the Babel Plugin should be the same to ensure this matches up. ### Better Guards on Global Scripts Solid uses an inline HydrationScript as a way to do processing before the framework and code have loaded. To handle things like event capture and streaming. However, we didn't do a good job of guarding the right thing when multiple were added to the same page, a situation that can happen in Micro-frontends or 3rd party Islands solutions. Now the script guards against duplicate inclusion.

Solid has experienced incredible growth in usage the past 6 months. Companies are using it to power production applications and SolidStart Beta has been a big part of that. As a natural part of this growth and increased use at scale we are continuing to learn what works well and what the rough edges in Solid are today. This v1.7 release marks the beginning of the migration roadmap to v2.0. We are beginning to re-evaluate core APIs and will begin introducing new ones while reasonably deprecating older ones in a manner that eases breaking changes. Our intention is to ease the broader ecosystem into preparing for improvements that a major 2.0 will unlock for the whole community. ## Improved TypeScript ### Null-Asserted Control Flow One of the pains of using Solid with TypeScript has been that JSX control flows can't really type narrow. This is true, but starting with the migration to explicit `keyed` in v1.5 we now complete this story by introducing callback forms for `<Show>` and `<Match>` that work when non-keyed. The main difference is the callback form instead of passing in the value as it does when `keyed`, passes in a function that is type narrowed. ```js // keyed w/ callback - reruns full callback on change <Show when={user()} keyed> {nonNullUser => <div>{nonNullUser.name}</div>} </Show> // non-keyed w/o callback... - only updates the one expression, needs ! assertion <Show when={user()}> <div>{user()!.name}</div> </Show> // NEW! // non-keyed w/ callback - only updates the one expression <Show when={user()}> {nonNullUser => <div>{nonNullUser().name}</div>} </Show> ``` Keep in mind because we are non-null asserting the input signal so it won't expect null in closures that execute when the condition is no longer satisfied. For this reason the accessor from the callback is special and will throw when attempted to be accessed when the condition is no longer true. This may be unexpected but it is our best attempt to keep TypeScript strict and not present inconsistency in reactivity. Luckily this only applies to things like timers which you should be cleaning up anyway and not things like event handlers. We recommend using the original conditions source in those closures if you must. ### Better Event Types for Input Elements This has irked people for a while but we come by it honestly, `target` is gives you a type of `Element` rather than the specific element that is the target. That means no access to `.value` or `.checked`. The reason is there is no way to know at compile time what the target of an event will be. The `currentTarget` will be the element you attach the event to but the target can be anything. There is a way to work around this though, in that if we know the `currentTarget` is of type that generates the event and that the `currentTarget` is the the type of this element we can assume it is the `target` as well. Not perfect logic but it is what React does and we do too. Now `onInput`, `onChange`, `onBlur`, `onFocus`, `onFocusIn`, and `onFocusOut` all support more detailed `target` when applied to `HTMLInputElement`, `HTMLTextAreaElement`, and `HTMLSelectElement`. ### Stricter JSX Elements Strict JSX elements have been tricky because we have to acknowledge at a certain point that TypeScript is to serve our purposes rather than to represent all possible values that could work. For us the ambiguity lies in functions. Solid's JSX needs to accept functions to handle dynamic insertion. However, in authoring it leads to awkward situations. The first you hit the first time use Solid. You create that counter and don't call `count` as a function and it works. ```js function Counter() { const [count, setCount] = createSignal(1); return <button onClick={() => setCount(c => c + 1)}>{count}</button>; } ``` This example works in some places and not others which might lead to the wrong conclusions. The second place you might hit this is when you get a little further on your journey and decide you need a component to re-render and decide that you can just wrap the whole thing in a function: ```js function MyComp(props) { return () => { // look working early returns if (props.count > 5) { return <div>Maximum Tries</div>; } return <div>Attempt {props.count}</div>; }; } ``` Again this seems fine, except the fact that every time `count` changes you are recreating all the DOM Elements even when it resolves to the same conditional. Eventually you might even not think twice about passing functions into children of arbitrary components: ```js <MyComp> <MyComp2> <MyComp3>{() => <div>{resource()}</div>}</MyComp3> </MyComp2> </MyComp> ``` But what does this do? When is the function called? As it turns out removing functions from `JSX.Element` type makes all of these scenarios error. Components only expect the values dictated by their types. ```js function MyLayout(props: { children: JSX.Element }): JSX.Element; function MyFor<T, U extends JSX.Element>(props: { each: T[], children: (item: T) => U }): JSX.Element; // valid <MyLayout>Hello</MyLayout> <MyLayout><p>Hello</p></MyLayout> <MyLayout>{name()}</MyLayout> <MyLayout>{name() && <p>Hello</p>}</MyLayout> <MyLayout>{(() => { return <p{name()}</p> })()}</MyLayout> <MyLayout>{untrack(() => { return <p>{name()}</p> })}</MyLayout> <MyFor each={users()}>{(user) => <div>{user.name}</div>}</MyFor> // invalid <MyLayout>{name}</MyLayout> <MyLayout>{() => <p>Hello</p>}</MyLayout> <MyLayout>{() => "Hello"}</MyLayout> <MyLayout>{() => name() && <p>Hello</p>}</MyLayout> <MyFor each={users}>{(user) => <div>{user.name}</div>}</MyFor> <MyFor each={users()}><div>Not a Function</div></MyFor> ``` The tradeoff here is that authoring components you can no longer just return a Signal or Memo without casting. If using JSX you can always return a Fragment. If not you will need to cast to `unknown as JSX.Element`. ## Better Errors ### `catchError` replaces `onError` Error Handling is complicated enough without having to try to guess how they propagate. `onError` admittedly is a lower level primitive but fundamentally had this flaw. It worked by registering an error handler on the parent scope, but left it ambiguous how to handle siblings. Is it a queue? Are they independent? As a result we are introducing `catchError` in this release which introduces its own scope to catch any errors below it. The first argument in the primitive is similar to the try and the second argument is the catch. ```js catchError( () => { // do stuff throw new Error("I've Errored"); }, err => console.log(err) ); ``` `onError` will still be present until it can be removed in a future major version. ### Standardized Errors Error Handling has had many weird edge cases introduced by applications throwing unusual values. In v1.7 we wrap all thrown values that aren't of type `Error` in a `new Error` and attach the original thrown value as `.cause`. ## More Performant Dev Tools Now that [Solid Dev Tools](https://github.com/thetarnav/solid-devtools) have been stabilizing, we have a much better idea what support we need for them. In so we were able to remove the very costly serialization we were doing for generating unique identifiers. Conventions around naming and exports were streamlined and standardized as well. ## Others - Smaller compiled output, remove auxilary closing tags - Support for `prop:` and `attr:` in Spreads - Don't apply special props (like `readonly`) to custom elements - Reverse cleanup execution order at the same level - Introduced improved serializer, [seroval](https://github.com/lxsmnsyc/seroval) - Fixed quirks in Solid's treeshaking in Rollup - Minify inline class and style attributes - Update `solid-ssr` to type `"module"` - Test Suite moved to Vitest Big thanks to @lxsmnsyc, @thetarnav, @niccholaspage, @atk, @Exelord, @jpdutoit, @titoBouzout, @MarkChrisLevy, @ulivz for your contributions and to everyone who contributed missing JSX types. Also to @LiQuidProQuo, @fabiospampinato for challenging decisions. This was the most difficult release we had in terms of making decisions due to the impact it has on TypeScript so it was valuable seeing the other opinion. Finally special shoutout to @otonashixav, who is our guiding light in terms of TypeScript and is the only way a release like this happens.