Brad Arant
97142ce9b4
Found while writing a new Expressions Reference chapter for the manual,
where every function got run for real before being documented rather
than trusted from reading the source alone - substring('helloworld', 7)
threw "operand is not valid." immediately after producing the correct
answer, confirmed via debug tracing showing an extra Operand constructed
on empty input right after the 2-arg case finished.
Root cause: a missing pair of braces around the 3-argument-only branch
meant Operand parm3(in, tag) and its own closing-paren check ran
unconditionally, even after the 2-arg form's own "if(in.ifNext(')'))"
check had already matched and produced string = parm1.string.substring(
parm2.string.asInteger()) - so it immediately tried to parse a third
argument from whatever was left (nothing, since the real closing paren
was already consumed), and construction on empty input always throws.
The 3-argument form (substring(str, start, length)) was unaffected,
since its own path never hit the first if-branch's early exit.
Fixed by properly scoping the 3-arg branch inside an else, so it only
runs when the 2-arg form's own closing paren wasn't found. Verified both
forms with real jet-2.0 runs: substring('helloworld', 7) -> "rld",
substring('helloworld', 0, 5) -> "hello".