refactor(template-compiler): change invalid template attributes from warning to error

[jmsjtu]

Details

This PR increases the strictness of the template compiler syntax by throwing an error instead of a warning when invalid template attributes are detected.

There are two scenarios that are affected by this change:

1. The template only contains invalid template attributes
2. The template contains a mix of valid and invalid attributes.

Scenario 1 example:

<template class="hello">
    <p>hi</p>
</template>

Will now throw an error and will not render the contents of the template.

Scenario 2 example:

<template if:true={showItems} for:each={items} for:item="item" onfoo={handleFoo}>
    <p key={item.id}>1{item}</p>
 </template>

In the second scenario, the current behavior is for the template to ignore the invalid attributes (onfoo) but continue to render the rest of the child elements and apply the valid attributes (if:true, for:each, and for:item).

After this change, the new behavior will throw an error and not emit the child elements.

Does this pull request introduce a breaking change?

• 🚨 Yes, it does introduce a breaking change.

• Adding a new restriction to the compiler which might result in a compilation failure for existing code. See above for description of changes.

Does this pull request introduce an observable change?

• ⚠️ Yes, it does include an observable change.

• Adding a new restriction to the compiler which might result in a compilation failure for existing code. See above for description of changes.

GUS work item

W-11296404