Track TagHelperAttribute quotes

[NTaylorMullen]

This would enable TagHelper users to write things like <input type=checkbox /> and have it output the identical code; whereas today we output <input type="checkbox" />.

This change would actually have a significant perf impact as well. Today in TagHelperOutput we have to write an attribute to an intermediate writer to potentially escape any double quotes in the case that a user wrote <input type=' """" ' /> since we always output with double quotes.

This intermediate writing step in my tests have represented over 5% of allocations.

[Eilon]

Is preserving the non-quotes actually important?

Also, what happens if a Tag Helper modifies that attribute? Does it "gain" the quotes after it's modified? E.g. let's say in my Tag Helper I set OutputTags["type"] = "this has spaces"; (or whatever the syntax is). Does it render <input type=this has spaces /> or <input type="this has spaces" />?

[NTaylorMullen]

Actually, with the new immutability of TagHelperAttributes the unquoted scenario isn't an issue. For instance, if a TagHelper author were to do output.Attributes.SetAttribute("type", "...") they'd be saying "create a new TagHelperAttribute with name type and value ..." which would default to using a double quoted value. If they instead used the TagHelperAttribute attribute overload they'd have the option of using their own quoting.

A user would have to purposefully shoot themselves in the foot and do something like:

var myBadAttribute = new TagHelperAttribute("type", "this has spaces", QuoteType.Unquoted);
output.Attributes.SetAttribute(myBadAttribute);

[NTaylorMullen]

e14f4b0
aspnet/Mvc@cfd58f1