JEP 430 String Templates, some weird scenarios feedback

[Brian Goetz]

On 6/15/2023 6:01 PM, Anatoly Kupriyanov wrote:
> I understand why it works like that but it still causes some confusion 
> to me, at least it should be somehow documented:
>
> var val = 1; var template = RAW."val = \{val}"; assert 
> template.interpolate().equals("val = 1");
> val = 2; assert template.interpolate().equals("val = 1");//weird

Yes, a template closes over values, not variables.  We could adopt the 
same constraint as we do with lambdas / inner classes -- require that 
any referenced variables be effectively final -- but this would likely 
be quite restrictive given the typical use cases for string templates.

>
> Another thing, I could not figure out a reasonable conditional 
> template syntax and nesting. This looks kind of ugly and hard to read
>
> String msg(String name, String val)
> { return STR."Today is a nice day. \{name == null ? "" : STR."Hello 
> \{name}! "}You have \{val}thing.";
> }
> assert msg(null, "this").equals("Today is a nice day. You have this 
> thing."); assert msg("World", "that").equals("Today is a nice day. 
> Hello World! You have that thing.");
>
> This thing would be especially important e.g. for a JSON tree templating.
>

Whenever you have an expression that is so complicated or deeply nested 
that it is hard to read, the standard trick is to break it up.  This is 
not unique to string templates.

     var n = (name == null) ? "" : STR."Hello \{name}! ";
     return STR."Today is a nice day. \{n}  You have \{val} thing.";

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