TemplatedString.builder() produces mutable TemplateString?

[Nathan Walker]

Hey folks,

I was poking around at the source in the templated-string branch and saw
something that seemed odd.

In the TemplatedString.TemplateBuilder.build() method there is:

/**
 * Returns a {@link TemplatedString} based on the current state of the
 * {@link TemplateBuilder Builder's} fragments and values.
 *
 * @return a new TemplatedString
 */
public TemplatedString build() {

return new SimpleTemplatedString(Collections.unmodifiableList(fragments),
Collections.unmodifiableList(values));

}


And SimpleTemplatedString is just:


record SimpleTemplatedString(List<String> fragments, List<Object> values)
implements TemplatedString {}


There doesn't seem to be any defensive copying of the fragments and values
lists, just wrapping in the unmodifiableList() call.  So it is unmodifiable
but if a builder is reused I then I believe those lists could change.

var builder = TemplatedString.builder();
TemplatedString ts = builder

.fragment("a:").value(1)

.fragment(", b:").value(2)

.build();


String result = STR.apply(ts); // result = "a:1, b:2"


builder.fragment(", c:").value(3);
result = STR.apply(ts); // result = "a:1, b:2, c:3" - same TempaltedString,
very different result

Is this behavior intended? Based on the documentation on TemplatedString I
wouldn't have thought so, but perhaps I am missing something.

Thanks for your time.
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