.cursorrules Cursor AI Prompt for Svelte 5 & SvelteKit 2

Svelte 5 SvelteKit 2 .cursorrules prompt file

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Sumanth Chinthagunta

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Svelte 5 SvelteKit 2 .cursorrules prompt file

I'm using svelte 5 instead of svelte 4 here is an overview of the changes.

Overview

Svelte 5 introduces runes, a set of advanced primitives for controlling reactivity. The runes replace certain non-runes features and provide more explicit control over state and effects.

$state

Purpose: Declare reactive state.
Usage:

`<script>`let count = $state(0);`</script>`

Replaces: Top-level let declarations in non-runes mode.
Class Fields:

class Todo {	done = $state(false);	text = $state();	constructor(text) {		this.text = text;	}}

Deep Reactivity: Only plain objects and arrays become deeply reactive.

$state.raw

Purpose: Declare state that cannot be mutated, only reassigned.
Usage:

`<script>`let numbers = $state.raw([1, 2, 3]);`</script>`

Performance: Improves with large arrays and objects.

$state.snapshot

Purpose: Take a static snapshot of $state.
Usage:

`<script>`	let counter = $state({ count: 0 });	function onClick() {		console.log($state.snapshot(counter));	}`</script>`

$derived

Purpose: Declare derived state.
Usage:

`<script>`let count = $state(0); let doubled = $derived(count * 2);`</script>`

Replaces: Reactive variables computed using $: in non-runes mode.

$derived.by

Purpose: Create complex derivations with a function.
Usage:

`<script>`	let numbers = $state([1, 2, 3]); let total = $derived.by(() => numbers.reduce((a, b) => a + b,	0));`</script>`

$effect

Purpose: Run side-effects when values change.
Usage:

`<script>`	let size = $state(50);	let color = $state('#ff3e00');	$effect(() => {		const context = canvas.getContext('2d');		context.clearRect(0, 0, canvas.width, canvas.height);		context.fillStyle = color;		context.fillRect(0, 0, size, size);	});`</script>`

Replacements: $effect replaces a substantial part of $: {} blocks triggering side-effects.

$effect.pre

Purpose: Run code before the DOM updates.
Usage:

`<script>`	$effect.pre(() =>{' '}	{		// logic here	}	);`</script>`

Replaces: beforeUpdate.

$effect.tracking

Purpose: Check if code is running inside a tracking context.
Usage:

`<script>`console.log('tracking:', $effect.tracking());`</script>`

$props

Purpose: Declare component props.
Usage:

`<script>`let {(prop1, prop2)} = $props();`</script>`

Replaces: export let syntax for declaring props.

$bindable

Purpose: Declare bindable props.
Usage:

`<script>`let {(bindableProp = $bindable('fallback'))} = $props();`</script>`

$inspect

Purpose: Equivalent to console.log but re-runs when its argument changes.
Usage:

`<script>`let count = $state(0); $inspect(count);`</script>`

$host

Purpose: Retrieve the this reference of the custom element.
Usage:

`<script>`	function greet(greeting) {		$host().dispatchEvent(new CustomEvent('greeting', { detail: greeting }));	}`</script>`

Note: Only available inside custom element components on the client-side.

Overview of snippets in svelte 5

Snippets, along with render tags, help create reusable chunks of markup inside your components, reducing duplication and enhancing maintainability.

Snippets Usage

Definition: Use the #snippet syntax to define reusable markup sections.
Basic Example:

{#snippet figure(image)}	`<figure>`		`<img src={image.src} alt={image.caption} width={image.width} height={image.height} />`		`<figcaption>`{image.caption}`</figcaption>`	`</figure>`{/snippet}

Invocation: Render predefined snippets with @render:

{@render figure(image)}

Destructuring Parameters: Parameters can be destructured for concise usage:

{#snippet figure({ src, caption, width, height })}	`<figure>`		`<img alt={caption} {src} {width} {height} />`		`<figcaption>`{caption}`</figcaption>`	`</figure>`{/snippet}

Snippet Scope

Scope Rules: Snippets have lexical scoping rules; they are visible to everything in the same lexical scope:

`<div>`	{#snippet x()}		{#snippet y()}...{/snippet}		`<!-- valid usage -->`		{@render y()}	{/snippet}	`<!-- invalid usage -->`	{@render y()}`</div>``<!-- invalid usage -->`{@render x()}

Recursive References: Snippets can self-reference or reference other snippets:

{#snippet blastoff()}	`<span>`🚀`</span>`{/snippet}{#snippet countdown(n)}	{#if n > 0}		`<span>`{n}...`</span>`		{@render countdown(n - 1)}	{:else}		{@render blastoff()}	{/if}{/snippet}{@render countdown(10)}

Passing Snippets to Components

Direct Passing as Props:

`<script>`	import Table from './Table.svelte';	const fruits = [{ name: 'apples', qty: 5, price: 2 }, ...];`</script>`{#snippet header()}	`<th>`fruit`</th>`	`<th>`qty`</th>`	`<th>`price`</th>`	`<th>`total`</th>`{/snippet}{#snippet row(fruit)}	`<td>`{fruit.name}`</td>`	`<td>`{fruit.qty}`</td>`	`<td>`{fruit.price}`</td>`	`<td>`{fruit.qty * fruit.price}`</td>`{/snippet}`<Table data={fruits} {header} {row} />`

Implicit Binding:

`<table data="{fruits}">`	{#snippet header()}	`<th>`fruit`</th>`	`<th>`qty`</th>`	`<th>`price`</th>`	`<th>`total`</th>`	{/snippet} {#snippet row(fruit)}	`<td>`{fruit.name}`</td>`	`<td>`{fruit.qty}`</td>`	`<td>`{fruit.price}`</td>`	`<td>`{fruit.qty * fruit.price}`</td>`	{/snippet}`</table>`

Children Snippet: Non-snippet content defaults to the children snippet:

`<table data="{fruits}">`	`<th>`fruit`</th>`	`<th>`qty`</th>`	`<th>`price`</th>`	`<th>`total`</th>`	`<!-- additional content -->``</table>``<script>`	let { data, children, row } = $props();`</script>``<table>`	`<thead>`		`<tr>`			{@render children()}		`</tr>`	`</thead>`	`<!-- table body -->``</table>`

Avoid Conflicts: Do not use a prop named children if also providing content inside the component.

Typing Snippets

TypeScript Integration:

`<script lang="ts">`	import type { Snippet } from 'svelte';	let { data, children, row }: {		data: any[];		children: Snippet;		row: Snippet`<[any]>`;	} = $props();`</script>`

Generics for Improved Typing:

`<script lang="ts" generics="T">`	import type { Snippet } from 'svelte';	let { data, children, row }: {		data: T[];		children: Snippet;		row: Snippet`<[T]>`;	} = $props();`</script>`

Creating Snippets Programmatically

Advanced Use: Create snippets programmatically using createRawSnippet where necessary.

Snippets and Slots

Mixing with Slots: Slots are deprecated but still work. Snippets provide more flexibility and power.
Custom Elements: Continue using <slot /> for custom elements as usual.

Sure! Here are the succinct instructions for handling Event Handlers in Svelte 5, tailored for the AI-integrated code editor to help it understand and utilize these features effectively.

Custom Instructions for Svelte 5 Event Handlers in Cursor AI

Overview

In Svelte 5, event handlers are treated as properties, simplifying their use and integrating them more closely with the rest of the properties in the component.

Basic Event Handlers

Declaration: Use properties to attach event handlers.

`<script>`	let count = $state(0);`</script>``<button onclick={() =>` count++}>	clicks: {count}`</button>`

Shorthand Syntax:

`<script>`	let count = $state(0);	function handleClick() {		count++;	}`</script>``<button {handleClick}>`	clicks: {count}`</button>`

Deprecation: The traditional on: directive is deprecated.

Component Events

Replacing createEventDispatcher: Components should accept callback props instead of using createEventDispatcher.

`<script>`	import Pump from './Pump.svelte';	let size = $state(15);	let burst = $state(false);	function reset() {		size = 15;		burst = false;	}`</script>``<Pump	inflate={(power) =>` { size += power; if (size > 75) burst = true; }}	deflate={(power) => { if (size > 0) size -= power; }}/>{#if burst}	`<button onclick={reset}>`new balloon`</button>`	`<span class="boom">`💥`</span>`{:else}	`<span class="balloon" style="scale: {0.01 * size}">` 🎈 `</span>`{/if}

Bubbling Events

Accept Callback Props:

`<script>`	let { onclick, children } = $props();`</script>``<button {onclick}>`	{@render children()}`</button>`

Spreading Props:

`<script>`	let { children, ...props } = $props();`</script>``<button {...props}>`	{@render children()}`</button>`

Event Modifiers

Avoiding Modifiers: Modifiers like |once, |preventDefault, etc., are not supported. Use wrapper functions instead.
Example Wrapper Functions:

`<script>`	function once(fn) {		return function (event) {			if (fn) fn.call(this, event);			fn = null;		};	}	function preventDefault(fn) {		return function (event) {			event.preventDefault();			fn.call(this, event);		};	}`</script>``<button onclick={once(preventDefault(handler))}>`...`</button>`

Special Modifiers: For capture:

`<button onclickcapture={...}>`...`</button>`

Multiple Event Handlers

Combining Handlers: Instead of using multiple handlers, combine them into one.

`<button	onclick={(e) =>` {		handlerOne(e);		handlerTwo(e);	}}>	...`</button>`

examples old vs new

Counter Example

Svelte 4 vs. Svelte 5:
Before:
```html
<script>
let count = 0;
$: double = count * 2;
$: {
if (count > 10) alert('Too high!');
}
</script>
<button on:click="{()" ="">count++}> {count} / {double}</button>
```
After:
```html
<script>
let count = $state(0);
let double = $derived(count * 2);
$effect(() => {
if (count > 10) alert('Too high!');
});
</script>
<button onclick="{()" ="">count++}> {count} / {double}</button>
```

Tracking Dependencies

Svelte 4 vs. Svelte 5:
Before:
```html
<script>
let a = 0;
let b = 0;
$: sum = add(a, b);
function add(x, y) {
return x + y;
}
</script>
<button on:click="{()" ="">a++}>a++</button>
<button on:click="{()" ="">b++}>b++</button>
<p>{a} + {b} = {sum}</p>
```
After:
```html
<script>
let a = $state(0);
let b = $state(0);
let sum = $derived(add());
function add() {
return a + b;
}
</script>
<button onclick="{()" ="">a++}>a++</button>
<button onclick="{()" ="">b++}>b++</button>
<p>{a} + {b} = {sum}</p>
```

Untracking Dependencies

Svelte 4 vs. Svelte 5:
Before:
```html
<script>
let a = 0;
let b = 0;
$: sum = a + noTrack(b);
function noTrack(value) {
return value;
}
</script>
<button on:click="{()" ="">a++}>a++</button>
<button on:click="{()" ="">b++}>b++</button>
<p>{a} + {b} = {sum}</p>
```
After:
```html
<script>
import { untrack } from 'svelte';
let a = $state(0);
let b = $state(0);
let sum = $derived(add());
function add() {
return a + untrack(() => b);
}
</script>
<button onclick="{()" ="">a++}>a++</button>
<button onclick="{()" ="">b++}>b++</button>
<p>{a} + {b} = {sum}</p>
```

Simple Component Props

Svelte 5:
```html
<script>
let { count = 0 } = $props();
</script>
{count}
```

Advanced Component Props

Svelte 5:
```html
<script>
let { class: classname, ...others } = $props();
</script>
<pre class="{classname}">
{JSON.stringify(others)}
</pre>
```

Autoscroll Example

Svelte 4 vs. Svelte 5:
Before:
```html
<script>
import { tick, beforeUpdate } from 'svelte';
let theme = 'dark';
let messages = [];
let viewport;
let updatingMessages = false;
beforeUpdate(() => {
if (updatingMessages) {
const autoscroll =
viewport && viewport.offsetHeight + viewport.scrollTop > viewport.scrollHeight - 50;
if (autoscroll) {
tick().then(() => viewport.scrollTo(0, viewport.scrollHeight));
}
}
});
function handleKeydown(event) {
if (event.key === 'Enter') {
const text = event.target.value;
if (text) {
messages = [...messages, text];
updatingMessages = true;
event.target.value = '';
}
}
}
function toggle() {
theme = theme === 'dark' ? 'light' : 'dark';
}
</script>
<div class:dark="{theme" ="" ="" ="dark" }>
<div bind:this="{viewport}">
{#each messages as message}
<p>{message}</p>
{/each}
</div>
<input on:keydown="{handleKeydown}" />
<button on:click="{toggle}">Toggle dark mode</button>
</div>
```
After:
```html
<script>
import { tick } from 'svelte';
let theme = $state('dark');
let messages = $state([]);
let viewport;
$effect.pre(() => {
messages;
const autoscroll =
viewport && viewport.offsetHeight + viewport.scrollTop > viewport.scrollHeight - 50;
if (autoscroll) {
tick().then(() => viewport.scrollTo(0, viewport.scrollHeight));
}
});
function handleKeydown(event) {
if (event.key === 'Enter') {
const text = event.target.value;
if (text) {
messages = [...messages, text];
event.target.value = '';
}
}
}
function toggle() {
theme = theme === 'dark' ? 'light' : 'dark';
}
</script>
<div class:dark="{theme" ="" ="" ="dark" }>
<div bind:this="{viewport}">
{#each messages as message}
<p>{message}</p>
{/each}
</div>
<input onkeydown="{handleKeydown}" />
<button onclick="{toggle}">Toggle dark mode</button>
</div>
```

Forwarding Events

Svelte 5:
```html
<script>
let { ...props } = $props();
</script>
<button {...props}>a button</button>
```

Passing UI Content to a Component

Passing content using snippets:
```html

<script>
import Button from './Button.svelte';
</script>
<button>{#snippet children(prop)} click {prop} {/snippet}</button>

<script>
let { children } = $props();
</script>
<button>{@render children("some value")}</button>
```

I'm also using sveltekit 2 which also has some changes I'd like you to keep in mind

Redirect and Error Handling

In SvelteKit 2, it is no longer necessary to throw the results of error(...) and redirect(...). Simply calling them is sufficient.

SvelteKit 1:

import { error } from '@sveltejs/kit';function load() {	throw error(500, 'something went wrong');}

SvelteKit 2:

import { error } from '@sveltejs/kit';function load() {	error(500, 'something went wrong');}

Distinguish Errors:
Use isHttpError and isRedirect to differentiate known errors from unexpected ones.

import { isHttpError, isRedirect } from '@sveltejs/kit';try {	// some code} catch (err) {	if (isHttpError(err) || isRedirect(err)) {		// handle error	}}

Cookies now require a specified path when set, deleted, or serialized.

SvelteKit 1:

export function load({ cookies }) {	cookies.set(name, value);	return { response };}

SvelteKit 2:

export function load({ cookies }) {	cookies.set(name, value, { path: '/' });	return { response };}

Top-Level Promise Handling

Promises in load functions are no longer awaited automatically.

Single Promise:

SvelteKit 1:

export function load({ fetch }) {    return {        response: fetch(...).then(r => r.json())    };}

SvelteKit 2:

export async function load({ fetch }) {    const response = await fetch(...).then(r => r.json());    return { response };}

Multiple Promises:

SvelteKit 1:

export function load({ fetch }) {    return {        a: fetch(...).then(r => r.json()),        b: fetch(...).then(r => r.json())    };}

SvelteKit 2:

export async function load({ fetch }) {    const [a, b] = await Promise.all([        fetch(...).then(r => r.json()),        fetch(...).then(r => r.json())    ]);    return { a, b };}

`goto` Changes

goto(...) no longer accepts external URLs. Use window.location.href = url for external navigation.

Relative Paths Default

Paths are now relative by default, ensuring portability across different environments. The paths.relative config option manages this behavior.

Deprecated Settings and Functions

Server Fetches are no longer trackable.
preloadCode Arguments: Must be prefixed with the base path.
resolvePath Replacement: Use resolveRoute instead.

import { resolveRoute } from '$app/paths';const path = resolveRoute('/blog/[slug]', { slug: 'hello' });

Improved Error Handling

Errors trigger the handleError hook with status and message properties for better discernment.

Dynamic Environment Variables

Dynamic environment variables cannot be used during prerendering. Use static modules instead.

`use:enhance` Callback Changes

The properties form and data have been removed from use:enhance callbacks, replaced by formElement and formData.

Forms with File Inputs

Forms containing <input type="file"> must use enctype="multipart/form-data".

With these adjusted guidelines, your AI can now generate SvelteKit 2 code accurately while considering the migration changes.

stack:

Svelte 5

Sveltekit 2

TypeScript

Svelte 5 SvelteKit 2 .cursorrules prompt file

Sumanth Chinthagunta

About .cursorrules prompt file

What you can build

Svelte 5 Learning Platform: A comprehensive online platform offering interactive tutorials and exercises specifically focused on the new features and changes in Svelte 5, including runes, reactive state management, and snippets.
Svelte 5 Migration Tool: An automated tool that scans Svelte 4 projects and suggests or automatically applies necessary changes to upgrade them to Svelte 5, focusing on migrating reactive declarations, event handlers, and snippets.
Svelte Runed Dashboard: A web app template that leverages Svelte 5's runes and snippets to create highly dynamic and reactive dashboards, showcasing best practices with the new features.
SvelteKit Error Handling Helper: A plugin for SvelteKit 2 that simplifies error handling by providing visual cues and code snippets for using the new error handling functions and distinguishing between different error types.
Svelte 5 Code Snippet Library: A library of pre-made, reusable code snippets leveraging Svelte 5's $derived, $effect, and snippets for common use cases, available as a plugin for code editors.
Svelte 5 Course Generator: An online service to generate courses that teach Svelte 5 and SvelteKit 2, dynamically creating quizzes and projects that leverage new features like reactive bindings and error handling.
Svelte 5 Performance Analyzer: A tool that analyzes Svelte projects and suggests optimizations specific to Svelte 5, such as using $state.raw for large arrays and objects to improve performance.
Interactive Svelte 5 Cookbook: A recipe-style documentation site providing step-by-step guides on using Svelte 5 features in real-world applications, such as building components with deeply reactive state and leveraging $effect for animations.
Svelte 5 UI Component Library: A library of UI components built with Svelte 5, demonstrating how to use runes and snippets for advanced layouts and interactions.
Svelte 5 Responsive Layouts: A framework or set of templates to create responsive web apps using Svelte 5, focusing on the utilization of runes for state management and reactive layouts.
SvelteKit 2 Migration Assistant: A guided assistant tool that helps developers migrate their SvelteKit 1 projects to SvelteKit 2, offering insights on managing cookie paths and adapting redirect and error handling changes.
Svelte 5 Plugin for VSCode: A Visual Studio Code plugin that provides autocomplete, syntax highlighting, and documentation for Svelte 5's new features such as runes and event handlers as properties.
Svelte 5 UI Testing Suite: A set of testing tools specifically designed for apps using Svelte 5, incorporating testing for reactivity and runtime behavior of components using new primitives and $effect groups.
Svelte 5 Community Forum: An online community platform where developers can discuss the new features of Svelte 5, share best practices, and offer solutions for common migration and implementation challenges.
Svelte 5 Template Builder: A visual tool for creating and exporting Svelte 5 components and templates, utilizing its snippet and state management features to simplify the building of complex and interactive UI parts.

Benefits

Advanced Runes Primitives: Svelte 5's introduction of runes enhances state and effect management, replacing several non-runes features for improved control and reactivity.
Event Handler Simplification: Svelte 5 treats event handlers as properties, removing the need for the on: directive and integrating callback props for components.
Enhanced SvelteKit 2 Integration: Updates include direct error handling, path requirements in cookies, and changes in promise handling, enhancing portability and ensuring synchronous operations.

Synopsis

Developers upgrading projects from Svelte 4 to Svelte 5 and SvelteKit 1 to SvelteKit 2 will benefit by creating reactive UIs with advanced state management and handling updated error and redirect logic.

Overview of .cursorrules prompt

The .cursorrules file outlines the changes and new features in Svelte 5 and SvelteKit 2, focusing on reactivity and component handling. It introduces advanced primitives called runes for controlling reactivity and provides explicit control over state and effects through new concepts like `$state`, `$derived`, and `$effect`. These primitives replace some of the previous reactive methods and bring improvements in performance and maintainability. Additionally, the file addresses new ways to handle component props, snippets, and event handlers, demonstrating a shift from traditional methods to a more integrated property-based approach. For SvelteKit 2, handling redirects, errors, cookies, and promises has been simplified or altered, with a focus on improving code management and deployment flexibility. The document provides ample code examples to illustrate these updates, ensuring developers can transition smoothly to the new versions.

Svelte 5 SvelteKit 2 .cursorrules prompt file

Svelte 5 SvelteKit 2 .cursorrules prompt file

Svelte 5 SvelteKit 2 .cursorrules prompt file

About .cursorrules prompt file

What you can build

Benefits

Synopsis

Overview of .cursorrules prompt

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