Update on String Templates (JEP 459)

[Clement Cherlin]

On Wed, Mar 13, 2024 at 6:45 PM John Rose <john.r.rose at oracle.com> wrote:
>
> On 13 Mar 2024, at 15:22, John Rose wrote:
>
> > … OVERLOADS …
> >
> > I don’t see (maybe I missed it) a decisive objection to overloading across ST
> > and String, at least for some processing APIs.
>
> Perhaps it is this:  A language processor API that takes STs and never Strings is making it clear that all inputs should be properly vetted, nothing taken on trust as a bare string.
>
> Doing that MIGHT require a performance model which permits expensive vetting operations to be memoized on particular OCCURRENCES of inputs (not just the input strings viewed in and of themselves).
>
> If that’s true, then I guess that’s support for Guy’s proposal: That STs (even trivial ones) should never look identical to strings.  Maybe they should always be preceded by a sigil $, or (per my suggestion) they should always have at least one occurrence of \{ inside, even if it’s a trivial nop.
>
> I kind of like Guy’s offensive-to-everyone suggestion that $ is required to make a true ST.  Then it’s clear how the veteting APIs mate up with their vetted inputs.  And if $ is not placed in front, we surrender to the string-pasters, but at least the resulting true-string expressions won’t be accepted by the vetting APIs.

Adding an empty interpolated value to signal a template is not a
viable solution, because "\{}abc" is not equivalent to ST.of("abc").
Running the current preview,

RAW."\{}abc" produces StringTemplate{ fragments = [ "", "abc" ],
values = [null] } which interpolates to "nullabc".

RAW."abc" produces StringTemplate{ fragments = [ "abc" ], values = []
} which interpolates to "abc".

I strongly support using different quotes or a prefixed sigil over any
form of linguistic magic like "if an interpolated value is empty we
pretend it's not there but still treat the literal as a template" or
"a string literal can be implicitly converted to a template literal in
{context}".

Cheers,
Clement Cherlin