The goal here is to help users learn, through feedback, that a
StringTemplate is not a string, but a recipe for one, and if you want to
get that string, you have to cook it.
One way to help that along might be to have the toString look more like
that of a record:
StringTemplate{ segments = [ blah blah ], values = [ blah blah ] }
which will reinforce that you printed out a recipe and not the thing it
describes.
On 10/20/2022 10:44 AM, Tagir Valeev wrote:
Hello!
As stated in JEP 430 text, the string template is a well-formed
expression of StringTemplate type. Also, toString() method of
StringTemplate prints a debug-friendly representation like
[fragments](values) which is not intended for actual use. I can
imagine that the following mistake may happen often, especially by
inexperienced developers, or developers with background in other
languages:
int x = 10, y = 20;
System.out.println("\{x} plus \{y} equals \{x + y}");
Output expected by programmer: 10 plus 20 equals 30
Actual output (successfully compilable): ["", " plus ", " equals ",
""](10, 20, 30)
As an IDE vendor, we can surely provide an inspection for some
well-known methods like PrintStream#println(Object) with a quick-fix
to add a STR. prefix. However, not everybody uses IDEs. Probably the
language itself could help here somehow? E.g., uses of StringTemplate
where the Object type is expected might trigger a warning. This is
similar to array toString(), and every static analyzer has an
inspection about this. Honestly, I don't know a good solution but I
feel that it's not a good idea to introduce a new error-prone
construct, which is compilable and runnable, could be mistakenly used
and doesn't make sense.
As we are here, is it planned to specify StringTemplate equals and
hashCode? It's naturally a tuple of (fragments, values) lists, so
equals and hashCode could be defined. Also, current draft [1] suggests
that this is a non-sealed interface. Is it really intended to allow
third-party implementations?
Sorry if these questions were already discussed, I might skip some
discussions. I would be happy to see the pointers to previous
discussions.
With best regards,
Tagir Valeev
[1]http://cr.openjdk.java.net/~jlaskey/templates/docs/api/java.base/java/lang/template/StringTemplate.html
