* feat: make `<svelte:component>` unnecessary in runes mode
In Svelte 4, writing `<Component />` meant that the component instance is static. If you made the variable `Component` a reactive state variable and updated the component value, the component would not be reinstantiated with the new value - you had to use `<svelte:component>` for that. One reason was that having a dynamic component was more overhead, which is no longer the case in Svelte 5. We can therefore reduce the potential API surface area (by maybe deprecating `<svelte:component>` in the future) by allowing Svelte to recognize when a component variable is potentially dynamic. It turned out that this was already mostly the case. This PR fixes one case where it wasn't, and fixes another where this was wrongfully applied in legacy mode.
* we already have this function
* add interactive demos
* changeset
---------
Co-authored-by: Rich Harris <rich.harris@vercel.com>
Now that we've made `mount` and `hydrate` not call `flushSync` anymore, we can go back to using `queue_microtask` inside `#await`, which means people who want to synchronously see the pending block can do so using `flushSync` (as validated by our tests). This essentially reverts #12274
* chore: document `@html` and `<img src>` hydration change
Also add a test for it
closes#12333
* add a test
* Update sites/svelte-5-preview/src/routes/docs/content/03-appendix/02-breaking-changes.md
Co-authored-by: Rich Harris <rich.harris@vercel.com>
* lint
* update example and wording
* update test
* since it turns out we already had a test, we can delete the new one
* fix test
---------
Co-authored-by: Rich Harris <rich.harris@vercel.com>
* chore: reenable server CSS output through a compiler option
There are various use cases where this continues to be necessary/nice to have:
- rendering OG cards
- rendering emails
- basically anything where you use `render` manually and want to quickly stitch together the CSS without setting up an elaborate tooling chain
* cssRenderOnServer -> css: 'injected'
* update tests
* move append_styles into new module, update implementation
* get HMR working
* don't append styles to head when compiling as a custom element
* update changeset
* tweak
* tweak
* tweak wording
* update test
* fix
* reinstate optimisation, but without the bug
* fix sourcemap test
* move breaking change note
* Update packages/svelte/src/internal/server/index.js
Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>
---------
Co-authored-by: Simon Holthausen <simon.holthausen@vercel.com>
Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>
* breaking: play transitions on `mount` by default
closes#11280
* only prevent transitions when the component is invalidated
---------
Co-authored-by: Rich Harris <rich.harris@vercel.com>
* docs: make legacy.componentApi more visible
People didn't know that this exists, so we should make it more visible through having it be part of the error message, and calling it out in the docs with more details
* clarify
* flesh out message, put error behind a function
* make it work with HMR
* fix
* fix
* this makes it work. i don't fully understand why
* changeset
* changeset
* Delete .changeset/twelve-foxes-press.md
---------
Co-authored-by: Rich Harris <rich.harris@vercel.com>
In Svelte 3 and 4, components were classes under the hood, and the base class was `SvelteComponent`. This class was also used in language tools to properly type check the template code.
In Svelte 5, components are functions. To give people a way to extend them programmatically, it would be good to expose the actual shape of components. This is why this PR introduces a new `Component` type.
For backwards compatibility reasons, we can't just get rid of the old class-based types. We also need to ensure that language tools can work with both the new and old types: There are many libraries out there that provide `d.ts` files with type definitions written using the class types - these should not error.
That's why there's an accompagning language tools PR (https://github.com/sveltejs/language-tools/pull/2380) that's doing the heavy lifting: Instead of generating classes, it now generates a constant and an interfaces and uses Typescript's declaration merging feature to provide both so we can declare a component export as being both a class and a function. That ensures that people can still instantiate them with `new` (which they can do if they use the `legacy.componentApi` compiler option), and it also ensure we don't need to adjust any other code generation mechanisms in language tools yet - from a language tools perspective, classes are still the norm. But through exposing the default export as being _also_ callable as a function we can in a future Svelte version, where classes/the Svelte 4 syntax are removed completely, seamlessly switch over to using functions in the code generation, too, and the `d.ts` files generated up until that point will support it because of the dual shape. This way we have both backwards and forwards compatibility.
* breaking: disallow string literal values in `<svelte:element this="...">`
* note breaking change
* Update sites/svelte-5-preview/src/routes/docs/content/03-appendix/02-breaking-changes.md
Co-authored-by: Jeremiasz Major <jrh.mjr@gmail.com>
* prettier
* make invalid `<svelte:element this>` a warning instead of an error (#11641)
* make it a warning instead of an error
* format
---------
Co-authored-by: Jeremiasz Major <jrh.mjr@gmail.com>
* fix: mark `accessors` and `immutable` as deprecated
* add warnings for deprecated <svelte:options> attributes
* disable accessors in runes mode
* update tests
* tidy up
* the hell?
* regenerate types
* if I would get a dollar for every windows bug I fix I would be a millionaire by now
* return instance _and_ props in runes mode, move flushSync into shared code, don't set accessors in runes mode
* goddammit
* note breaking change
* fix
* regenerate messages
* Revert "return instance _and_ props in runes mode, move flushSync into shared code, don't set accessors in runes mode"
This reverts commit a47827e57d.
* pass instance to tests
---------
Co-authored-by: Simon Holthausen <simon.holthausen@vercel.com>
* breaking: disallow binding to component exports in runes mode
Svelte 4 allowed you to have `export const foo = ..` in component A and then do `<A bind:foo />`. This is confusing because it's not clear whether the binding is for a property or an export, and we have to sanitize rest props from the export bindings.
This PR therefore introduces a breaking change in runes mode: You cannot bind to these exports anymore. Instead use `<A bind:this={a} />` and then do `a.foo` - makes things easier to reason about.
* Update sites/svelte-5-preview/src/routes/docs/content/03-appendix/02-breaking-changes.md
Co-authored-by: Rich Harris <rich.harris@vercel.com>
* tweak messages
* fix tests
* use component.name
* oops
---------
Co-authored-by: Rich Harris <rich.harris@vercel.com>
- don't throw a dev time error when binding to an export (fixes#11008)
- remove bindings that are for component exports
- throw an error when using a component export with the same name as a property
* feat: take form resets into account for two way bindings
When resetting a form, the value of the inputs within it get out of sync with the bound value of those inputs. This PR introduces a reset listener on the parent form to reset the value in that case
closes#2659
* slightly different approach
* tweaks, test
* this is a breaking change, strictly speaking
* bind:files
* use capture phase
* tweak wording
* use promise, explain
People could've done bind:this and called instance methods on the instance - a rare case, but not impossible. This shims $set and $on when in legacy compat mode. $destroy is never shimmed because you shouldn't manually destroy a component, ever, and there's no way to make that work in the new world.
closes#10420
Add source map merging for preprocessors and get tests passing.
- fixed some issues around the `sources` array where they weren't calculated relative to the input correctly
- adjusted some CSS tests because due to our own CSS parser the AST is less granular, so there are less mappings now. Don't think this is a problem, but worth thinking about
- removed enableSourcemap but only log a warning, the reason this was introduced was to mitigate a bug in Vite which occured when having the source map inlined into the SSR'd output. Since SSR doesn't contain inlined CSS anymore (and if it did, we would omit the source map) the reason for which it was introduced no longer exists
- files without js mapping in it have no source mappings yet (originally added in Svelte 4 for #6092)
Closes#9420.
This PR creates an $effect.pre (before beforeUpdate and an $effect (for afterUpdate) and, inside those, listen for all locally declared signals plus reactive props. This does mean that we need to link the locally declared signals to the component context (the reverse of the current behaviour, wherein we link the component context to locally declared signals).
Someone could programmatically add a class to an element and Svelte doesn't see it, so having global be part of a modifier is necessary so that Svelte doesn't mark it as unused
fixes#10210
* rename file
* add snippet docs
* add note on deprecation
* they're not attributes
* event docs
* prettier
* remove unnecessary div
* Apply suggestions from code review
Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>
* make example less confusing
* note breaking props.children change
---------
Co-authored-by: Rich Harris <rich.harris@vercel.com>
Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>
Simon H
Kohei Yoshino
Rich Harris
Dominic Gannaway
Luke Warlow
Rich Harris
Simon Holthausen
Erick Vargas
Yuichiro Yamashita