next: [data-state] Attribute Conflicts in Component Compositions

[max-got]

Describe the bug

Based on #823 , there's a systemic issue with component composition where multiple components using the same [data-state] attribute conflict with each other. IMO it is something to decide before 1.0. While the Toggle and Tooltip example demonstrates this problem, it affects any combination of components that rely on the [data-state](or similiar) attribute for styling and state management.

Current Behavior

• Multiple components use the same [data-state] attribute
• The last component in the composition overwrites the state of previous components
• CSS selectors targeting states of overwritten components become ineffective
• Only the last component's styles are applied

Expected Behavior

Elements should be styleable based on each component's state independently, regardless of how many components are composed together

Impact

• Breaks component composability
• Limits component reusability
• Prevents proper styling of multi-state elements
• Creates unpredictable behavior in complex component hierarchies
• Makes debugging difficult as state conflicts are not immediately apparent

Example

Details

<Tooltip.Trigger>
	{#snippet child({ props })}
		<Toggle.Root  {...props}>
			{#snippet child({ props })}
				<button {...props}>I have [data-state] from the Toggle, not from the Tooltip.</button>
			{/snippet}
		</Toggle.Root>
	{/snippet}
</Tooltip.Trigger>

Current Style Conflicts

Details

	button[data-state='off'] {
		background-color: orange;
	}

	button[data-state='on'] {
		background-color: green;
	}

	/* These don't work due to the state conflict */
	button[data-state='closed'] {
		border: 2px solid red;
	}

	button[data-state='delayed-open'] {
		border: 2px solid blue;
	}

Proposed Solutions

Solution 1: Component-Specific Data Attributes

Use distinct data attributes for each component type:

Each component gets its own attribute

/* Each component gets its own attribute */
[data-accordion-state='expanded'] { }
[data-dialog-state='open'] { }
[data-button-state='active'] { }
[data-tooltip-state='open'] { }
[data-toggle-state='on'] { }

Pros:

• Clear separation of concerns
• Eliminates state conflicts
• Predictable styling behavior
• Easier debugging
• Scales well with multiple components

Cons:

• Breaking change for existing implementations (even tho pre 1.0)
• More verbose HTML output

Solution 2: Combined State Values

Use a single data-state attribute with combined values:

button[data-state~="tooltip-closed"] { }
button[data-state~="toggle-on"] { }

Pros:

• Maintains single attribute pattern
• Supports unlimited component combinations
• Less breaking than separate attributes
• More explicit state management

Cons:

• More complex CSS selectors
• Longer attribute values
• More string manipulation required

Reproduction

https://stackblitz.com/edit/stackblitz-starters-xdgpeu?file=src%2Froutes%2F%2Bpage.svelte

Logs

No response

System Info

-

Severity

blocking an upgrade