This PR implements inline support of multi conditions using the following syntax:

<script>
  let animal = 'dog';
</script>

<section>
  Can fly ?
  {#switch animal}
    {:case "cat" || "dog"}
      <p>No</p>
    {:case "bird"}
      <p>Yes</p>
  {/switch}
</section>

Closes #1

RFC: Support multi conditions

This feature would allow to use multiple conditions in one case statement.

Motivation

This is the current syntax when we have multiple conditions rendering the same result:

<script>
  let animal = 'dog';
</script>

<section>
  Can fly ?
  {#switch animal}
    {:case "cat"}
      <p>No</p>
    {:case "dog"}
      <p>No</p>
    {:case "bird"}
      <p>Yes</p>
  {/switch}
</section>

Issues:

• Code is unnecessarily repeated.
• The same result is re-rendered if the value of animal switches from "cat" to "dog".

Detailed design

The current proposal implements an inline multi conditions syntax.

<script>
  let animal = 'dog';
</script>

<section>
  Can fly ?
  {#switch animal}
    {:case "cat" || "dog"}
      <p>No</p>
    {:case "bird"}
      <p>Yes</p>
  {/switch}
</section>

Alternatives

The "native" switch syntax which implements the {:break} statement has been considered. It would allow to combine multiple {:case} falling back to the same result.

However, we are skeptical about its cleanliness and it seems to lengthen the code. Compare the proposed design to the following:

<script>
  let animal = 'dog';
</script>

<section>
  Can fly ?
  {#switch animal}
    {:case "cat"}
    {:case "dog"}
      <p>No</p>
    {:break}
    {:case "bird"}
      <p>Yes</p>
    {:break}
  {/switch}
</section>

It would also require refactoring all the projects using the current syntax and adding a {:break} statement to each condition.

Unresolved questions

There aren't really any unresolved questions at this point. I'm just opening this RFC if anyone wants to express themselves towards the proposed changes.

In any case, if we decide to implement this feature, it will be in the next major version so we ensure it's non-breaking for the current projects using this package.

Credits

Thanks to those Reddit comments for raising the code repetition problem.