Syntax for empty string value

[Pike]

Right now, there's no syntax for an empty string value, AFAICT.

One way to think about that would be to just use

my-text =

The other way is to try to create a non-"" AST value that evaluates to "". One candidate would be

my-text = {""}

But that's also not allowed, 'cause quote-text is '"' (text-char - '"' | '\"')+ '"', note the + instead of a *.

I didn't investigate what the fall-out of allowing * would be.

[stasm]

As I'd like to use the first form for all messages (#63), my preference (and an ongoing intent) has been to go for the second form. It has the benefit of being explicit and clearly visually distinctive, which I find helpful in this case. A zero-length value is an edge-case and I'd like to mark it visually as such.

[stasm]

#83 clarified the requirements for quoted-text making {""} legal. Regarding the null value, here's the summary of the rules as defined by Syntax 0.5.

# ERROR: messages must have values or attributes.
message =

# ERROR: terms must have values.
-term =

# OK: messages can have no values.
message =
    .attr = An attribute

# ERROR: terms must always have values.
-term =
    .attr = An attribute

# OK: both values here are empty strings (length == 0).
message = {""}
-term = {""}

# OK: variant values can also be empty strings.
message =
    { $num ->
        [zero] {""}
        [one] One something.
       *[other] Many somethings.
    }

[stasm]

I talked to @Pike and @zbraniecki about this and they agreed to use {""} to denote empty strings. Closing.

[langpavel]

{""} is terrible for translators — they are not programmers. I must study grammar what is possible/how should I write it down.
I'm proposing #223