HTML indent calculation problem with comments

[KristofMorva]

If a HTML comment is the last entry in an indentation level, it expects the wrong level (always one indentation less).

For example the following example works as expected:

<div>
    <br>
    <!-- michalsnik rocks -->
    <br>
</div>

But if the comment is the last entry, we'll get a Expected indentation of 0 spaces but found 4 spaces error for the line of the comment:

<div>
    <br>
    <!-- michalsnik rocks -->
</div>

So it expects the comment to look like this:

<div>
    <br>
<!-- michalsnik rocks -->
</div>

I'd say, it's probably not what the author usually wants. I'd say it might be best to ignore indentation check for comments altogether, as we can't predict if the developer wants to comment out the last row, or write a comment for the closing tag.

[michalsnik]

Hi, I can confirm that currently comments are expected to have the same indent as their following tag. But usually comments are to be placed above the tag they are commenting, so I think it's kind of ok.
However I can see a case with some placeholder message:

<div>
  <some-item />
  <!-- place here more items -->
</div>

and indeed this is the case you shouldn't be warned about in my opinion. The way I see it is that we accept both previous tag indentation as well as the next.

On the other hand this would make the rule indeterministic and --fix might not work as you expect it to.

What do you think @mysticatea? You worked on this rule so you have more insight for sure.

[mysticatea]

Hmm, looks like a bug to me.

Indeed, core indent rule allows both indentations (same as the next token or the previous token) if the next token is a closing brace (}) for the following case:

if (a) {
    foo()

// Description for the else
} else {
    foo()
}

If I clone the code to Vue.js template then:

<div v-if="a">
    <some-item />

<!-- Description for the else. -->
</div><div v-else>
    <some-item />
</div>

I'm not sure whether this style is enough general or not.
If the style is not general, I think that we should fix this as a bug.

<div>
  <some-item />
  <!-- this is correct -->
</div>
<div>
  <some-item />
<!-- this is incorrect -->
</div>

[mysticatea]

Maybe we should consider similar cases.

<div>
    {{
        foo
        // This comment is adjusted to same as the next token }} currently.
        // I think this comment should be the same as the previous token.
    }}-{{
        bar
    }}
</div>

[michalsnik]

Alright, then I think we should just allow both prev and next token indentation for comments, and that's it.