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JReinholdJReinhold
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Merge pull request #302 from storybookjs/jeppe/improve-types
Fix types
2 parents 8d4ea75 + d926543 commit 0e01dcf

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‎README.md‎

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@@ -177,7 +177,6 @@ Similar to regular CSF, you can define a meta-level `render`-function, by refere
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import MyComponent from './MyComponent.svelte';
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const { Story } = defineMeta({
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// @ts-expect-error -- TypeScript does not know this is valid: https://github.com/sveltejs/language-tools/issues/2653
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render: template,
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// 👆 the name of the snippet as defined below (can be any name)
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});
@@ -204,9 +203,6 @@ Stories can still override this default snippet using any of the methods for def
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> [!NOTE]
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> Svelte has the limitation, that you can't reference a snippet from a `<script module>` if it reference any declarations in a non-module `<script>` (whether directly or indirectly, via other snippets). See [svelte.dev/docs/svelte/snippet#Exporting-snippets](https://svelte.dev/docs/svelte/snippet#Exporting-snippets)
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> [!IMPORTANT]
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> There is currently a bug in the Svelte language tools, which causes TypeScript to error with `TS(2448): Block-scoped variable 'SNIPPET_NAMAE' used before its declaration.`. Until that is fixed, you have to silent it with `//@ts-ignore` or `//@ts-expect-error`. See https://github.com/sveltejs/language-tools/issues/2653
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#### Custom export name
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Behind-the-scenes, each `<Story />` definition is compiled to a variable export like `export const MyStory = ...;`. In most cases you don't have to care about this detail, however sometimes naming conflicts can arise from this. The variable names are simplifications of the story names - to make them valid JavaScript variables.
@@ -237,35 +233,78 @@ If for some reason you need to access the [Story context](https://storybook.js.o
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### TypeScript
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Story snippets and args can be type-safe when necessary. The type of the args are inferred from the component props passed to `defineMeta`.
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Story template snippets can be type-safe when necessary. The type of the args are inferred from the `component` or `render` property passed to `defineMeta`.
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You can make your snippets type-safe with the `Args` and `StoryContext` helper types:
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If you're just rendering the component directly without a custom template, you can use Svelte's `ComponentProps` type and `StoryContext` from the addon to make your template snippet type-safe:
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```svelte
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<script module lang="ts">
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import { defineMeta, type Args, type StoryContext } from '@storybook/addon-svelte-csf';
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// 👆 👆 import those type helpers from this addon -->
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import { defineMeta, type StoryContext } from '@storybook/addon-svelte-csf';
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import { type ComponentProps } from 'svelte';
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import MyComponent from './MyComponent.svelte';
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const { Story } = defineMeta({
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component: MyComponent,
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});
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type Args = ComponentProps<MyComponent>;
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</script>
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<!-- 👇 use to infer `args` type from the `Story` component -->
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{#snippet template(args: Args<typeof Story>, context: StoryContext<typeof Story>)}
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<!-- 👆 use to infer `context` type from the `Story` component -->
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{#snippet template(args: Args, context: StoryContext<typeof Layout>)}
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<MyComponent {...args} />
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{/snippet}
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```
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If you need to customize the type of the `args`, you can pass in a generic type parameter to `defineMeta` that will override the types inferred from the component:
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If you use the `render`-property to define a custom template that might use custom args, the args will be inferred from the types of the snippet passed to `render`. This is especially useful when you're converting primitive args to snippets:
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```svelte
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const { Story } = defineMeta<{ anotherProp: boolean }>( ... );
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<script module lang="ts">
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import { defineMeta, type StoryContext } from '@storybook/addon-svelte-csf';
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import { type ComponentProps } from 'svelte';
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import MyComponent from './MyComponent.svelte';
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const { Story } = defineMeta({
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component: MyComponent,
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render: template, // 👈 args will be inferred from this, which is the Args type below
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argTypes: {
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children: {
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control: 'text',
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},
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footer: {
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control: 'text',
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},
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},
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});
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type Args = Omit<ComponentProps<MyComponent>, 'children' | 'footer'> & {
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children: string;
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footer?: string;
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};
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// OR use the Merge helper from the 'type-fest' package:
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type Args = Merge<
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ComponentProps<MyComponent>,
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{
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children: string;
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footer?: string;
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}
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>;
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</script>
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<!-- 👇 you need to omit 'children' from args to satisfy Svelte's constraints -->
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{#snippet template({ children, ...args }: Args, context: StoryContext<typeof MyComponent>)}
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<MyComponent {...args}>
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{children}
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{#snippet footer()}
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{args.footer}
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{/snippet}
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</MyComponent>
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{/snippet}
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```
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See [the `Types.stories.svelte` examples](./examples/Types.stories.svelte) on how to use complex types properly.
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### Legacy API
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Version 5 of the addon changes the API from v4 in key areas, as described above. However a feature flag has been introduced to maintain support for the `<Template>`-based legacy API as it was prior to v5.

‎examples/Button.stories.svelte‎

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@@ -1,8 +1,9 @@
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<script module lang="ts">
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import { defineMeta, type Args, type StoryContext } from '@storybook/addon-svelte-csf';
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import { defineMeta, type StoryContext } from '@storybook/addon-svelte-csf';
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import { fn } from '@storybook/test';
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import Button from './components/Button.svelte';
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import type { ComponentProps } from 'svelte';
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const onclickFn = fn().mockName('onclick');
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@@ -25,12 +26,11 @@
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},
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children: { control: 'text' },
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},
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//@ts-expect-error TS does not understand that the snippet is defined before this call
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render: template,
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});
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</script>
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{#snippet template(args: Args<typeof Story>, context: StoryContext<typeof Story>)}
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{#snippet template(args, context)}
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<Button {...args}>{args.children}</Button>
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{/snippet}
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‎examples/Templating.stories.svelte‎

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@@ -1,5 +1,5 @@
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<script module lang="ts">
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import { defineMeta, type Args } from '@storybook/addon-svelte-csf';
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import { defineMeta } from '@storybook/addon-svelte-csf';
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import { expect, within } from '@storybook/test';
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/**
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* reference any root-level snippet, for that snippet to be the fallback snippet,
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* that is used in any story without explicit template.
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*/
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//@ts-expect-error TS does not understand that the snippet is defined before this call
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render: defaultTemplate,
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});
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</script>
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{#snippet defaultTemplate(args: Args<typeof Story>)}
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{#snippet defaultTemplate(args: { text: string })}
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<h2 data-testid="heading">Default template</h2>
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<p>{args?.text}</p>
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{/snippet}
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{/snippet}
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</Story>
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{#snippet sharedTemplate(args: Args<typeof Story>)}
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{#snippet sharedTemplate(args: { text: string })}
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<h2 data-testid="heading">Shared template</h2>
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<p>{args?.text}</p>
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{/snippet}
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Example:
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```svelte
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{#snippet template(args: Args<typeof Story>)}
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{#snippet template(args: { text: string })}
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<SomeComponent {...args}>
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My custom template to reuse across several stories
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</SomeComponent>
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```svelte
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<script>
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import { defineMeta, type Args } from '@storybook/addon-svelte-csf';
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import { defineMeta } from '@storybook/addon-svelte-csf';
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const { Story } = defineMeta({
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...,
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render: defaultTemplate
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})
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</script>
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{#snippet defaultTemplate(args: Args<typeof Story>)}
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{#snippet defaultTemplate(args: { text: string })}
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<SomeComponent {...args}>
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A default template to be used in <Story> components which doesn't have an explicit template set
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</SomeComponent>

‎examples/Types.stories.svelte‎

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<script lang="ts" module>
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import { defineMeta, type StoryContext } from '@storybook/addon-svelte-csf';
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import Layout from './components/Layout.svelte';
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import type { ComponentProps } from 'svelte';
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import type { Merge } from 'type-fest';
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const { Story } = defineMeta({
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component: Layout,
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render: template,
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args: {
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mainFontSize: 'large',
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header: 'default header',
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},
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argTypes: {
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footer: {
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control: 'text',
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},
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children: {
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control: 'text',
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},
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header: {
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control: 'text',
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},
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},
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tags: ['autodocs'],
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});
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type Args = Omit<ComponentProps<typeof Layout>, 'footer' | 'children' | 'header'> & {
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footer?: string;
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children: string;
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header: string;
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};
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// OR use the Merge helper from the 'type-fest' package:
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type SimplerArgs = Merge<
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ComponentProps<typeof Layout>,
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{
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footer?: string;
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children: string;
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header: string;
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}
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>;
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</script>
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{#snippet template({ children, ...args }: Args, context: StoryContext<Args>)}
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<Layout {...args}>
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{#snippet header()}
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{args.header}
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{/snippet}
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{children}
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{#snippet footer()}
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{args.footer}
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{/snippet}
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</Layout>
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{/snippet}
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<Story name="Default" />
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<Story
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name="With all args"
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args={{
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mainFontSize: 'large',
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header: 'Header',
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footer: 'Footer',
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children: 'Children',
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emphasizeHeader: true,
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}}
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/>
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<Story name="With mainFontSize" args={{ mainFontSize: 'small' }} />
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<Story name="With String Header" args={{ header: 'Header' }} />
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<Story name="With static Header and Footer snippets">
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{#snippet template({ children, ...args }, context)}
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<Layout {...args}>
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{#snippet header()}
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This is a header
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{/snippet}
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{children}
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{#snippet footer()}
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This is a footer
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{/snippet}
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</Layout>
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{/snippet}
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</Story>

‎examples/components/Layout.svelte‎

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<script lang="ts">
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import type { Snippet } from 'svelte';
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type LayoutProps = {
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children: Snippet;
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header: Snippet;
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footer?: Snippet;
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mainFontSize: 'small' | 'medium' | 'large';
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emphasizeHeader?: boolean;
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};
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let { children, header, footer, emphasizeHeader = false, mainFontSize }: LayoutProps = $props();
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</script>
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<div class="layout">
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<div class={['header', emphasizeHeader && 'emphasize']}>
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{@render header()}
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</div>
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<main
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class={[
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'main',
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{
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'font-small': mainFontSize === 'small',
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'font-medium': mainFontSize === 'medium',
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'font-large': mainFontSize === 'large',
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},
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]}
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>
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{@render children()}
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</main>
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{#if footer}
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<div class="footer">
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{@render footer()}
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</div>
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{/if}
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</div>
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<style>
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.layout {
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display: flex;
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flex-direction: column;
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height: 100%;
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}
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.layout > * {
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padding: 1rem;
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}
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.header,
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.footer {
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background-color: palevioletred;
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color: white;
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}
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.header.emphasize {
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background-color: red;
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}
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.main.font-small {
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font-size: 12px;
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}
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.main.font-medium {
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font-size: 16px;
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}
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.main.font-large {
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font-size: 20px;
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}
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</style>

‎package.json‎

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"@tsconfig/svelte": "^5.0.4",
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"@types/estree": "^1.0.6",
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"@types/node": "^20.14.9",
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"@vitest/browser": "2.1.4",
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"@vitest/coverage-v8": "2.1.4",
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"@vitest/ui": "^2.1.4",
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"@vitest/browser": "^3.1.3",
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"@vitest/coverage-v8": "^3.1.3",
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"@vitest/ui": "^3.1.3",
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"auto": "^11.1.6",
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"chromatic": "^11.28.2",
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"concurrently": "^8.2.2",
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"rollup": "^4.25.0",
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"storybook": "^9.0.0-0",
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"svelte": "^5.28.2",
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"svelte-check": "^4.0.5",
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"svelte-check": "^4.1.7",
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"tslib": "^2.6.3",
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"type-fest": "^4.20.1",
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"typescript": "^5.5.2",
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"typescript-eslint": "^8.30.1",
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"typescript-svelte-plugin": "^0.3.42",
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"vite": "^5.4.11",
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"vite": "^6.3.5",
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"vite-plugin-inspect": "^0.8.7",
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"vite-plugin-virtual": "^0.3.0",
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"vitest": "^2.1.4"
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"vitest": "^3.1.3"
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},
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"peerDependencies": {
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"@storybook/svelte": "^0.0.0-0 || ^8.2.0 || ^9.0.0-0",

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