class: '' - A CSS class string.

For the sake of best compatibility we convert the className attribute to class for svelte.

Most simple example: <script> import ChildComponent from './Child.svelte'; </script> <style> .class-to-add { background-color: tomato; } </style> <ChildComponent class="class-to-add" /> ...compiles to CSS without the class-to-add declaration, as svelte currently does not recognize the class name as being used. I'd expect class-to-add is bundled with all nested style declarations class-to-add is passed to ChildComponent as class-to-add svelte-HASH This looks like a bug / missing feature to me.

color: red; //doesn't apply this rule, because scoping doesn't extend to children

Say I want to style this javascript routing anchor tag on various pages (some may be buttons, plain links, images) it makes it incredibly difficult. Eg:

Having to wrap everything in a selector :global(child) { } is hacky

There is a good amount of properties that should mostly be applied from a parent's point of view. We're talking stuff like grid-area in grid layouts, margin and flex in flex layouts. Even properties like position and and the top/right/left/bottom following it in some cases.

Svelte will not offer a generic way to support style customizing via contextual class overrides (as we'd do it in plain HTML). Instead we'll invent something new that is entirely different. If a child component is provided and does not anticipate some contextual usage scenario (style wise) you'd need to copy it or hack around that via :global hacks.

This allows passing classes to child components with svelte-{hash} through the class prop and prevents removing such classes from css.

The problem with working around the current limitations of Svelte style (:global, svelte:head, external styles or various wild card selectors) is that the API is uglier, bigger, harder to explain AND it loses one of the best features of Svelte IMO - contextual style encapsulation. I can understand that CSS classes are a bit uncontrollable, but this type of blocking will just push developers to work around it and create worse solutions.

However, we've another unresolved problem - passing parent's styles to child components.