"flag" attributes

[panglesd]

Hello !

The djot syntax reference does not allow flag attributes (attributes without a value, or empty attributes, as they are called in html).

I think those flag attributes are useful! Is there a reason for not supporting them?

(I would have the same question for pandoc's markdown, but since pandoc has so many more features, I though asking in this syntax-specific repo was better).

Anyway, thanks a lot for all your work on markup languages!

[jgm]

I'm open to reconsidering this. My thinking originally was that if we allow flag attributes there is greater chance of capturing something that was meant as regular text, e.g. {this is just plain text in braces}. But if we assume that braces are very rarely used in regular text, this isn't a big problem.

Semantically, how should flag attributes be represented? In HTML, checked is semantically equivalent to checked="checked" and also, I think, to checked="". So, we could parse a bare checked as a key-value attribute checked=checked.

[panglesd]

I could only find the equivalence of empty attributes with attributes with value "":

Empty attribute syntax
Just the attribute name. The value is implicitly the empty string.

Using the already existing equivalence of a flag/empty attributes with an attribute of value "" is indeed a good way to add the feature without changing the AST. Alternatively, there could be a new kind of attributes, "flag" attributes, which have a key but not a value.

[bpj]

A possible value for the representation of flag attributes in the AST would be true: element.checked would be true in boolean context but you could also do if ( element.checked == true ) to distinguish {checked} from {checked=checked} for better roundtripping.

In Pandoc Markdown I always use backslashes or verbatim for non-attribute braces but TBH I also always disable shortcut reference links so that I don’t have to remember to escape brackets around phonetic transcriptions! I do occasionally use braces around shorthand transliterations¹ but I use verbatim with a class for those. I would believe that braces are even more unusal in text than brackets but there probably is some discipline which uses braces a lot! However I don’t think djot should disallow flag attributes because of that.

Footnotes

1. Because shorthand is difficult to reproduce in electronic documents it is common to use a longhand transcription like {InTrODUKTion} where {In}, {Tr}, and {Tion} represent a single shorthand grapheme each, i.e. each shorthand grapheme is represented by an uppercase letter followed by zero or more lowercase letters. Some punctuation and symbols are used as well. ↩