Fix support for empty attributes

[tmelliottjr]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)
• If applicable, I’ve added docs and tests

Description of changes

This change adds handling for attributes that are explicitly set with an empty string "" or all whitespace " ".

Prior to this, html comments that contained an empty string attribute were ignored completely.

For example, given the following html commentMarker returns null.

const html = '<!-- action target="1234" field="type" value="" -->'
const marker = commentMarker(node)
// marker === null

Additionally, attributes with whitespace only were coerced to number resulting in unexpected behavior.

For example, the following results in an attribute value of 0.

const html = '<!-- action target="1234" field="type" value=" " -->'
const marker = commentMarker(node)
// marker.parameters === {
//   target: 1234,
//   field: "type",
//   value: 0,
// }

[wooorm]

Thanks, released in 2.1.2!!

[mikesurowiec]

@wooorm @tmelliottjr thank you both for this! 👏

[tmelliottjr]

Thank you for the quick 👀 on this, greatly appreciated!