Fix $range and $random ignoring zero-valued optional arguments

[gaoflow]

What

_builtin_range and _builtin_random use truthiness checks (if stop:,
if step:, if boundary:) to detect whether optional numeric arguments
were supplied. This is wrong when the argument value is 0, which is
falsy but a valid integer.

$range(start, stop=0)

$range(5, 0)   # returned [0, 1, 2, 3, 4] — should be []

stop=0 evaluated as falsy, so the function ignored it and called
range(int(start)) = range(5) instead of range(5, 0) = [].

$range(start, stop, step=0)

step=0 evaluated as falsy, so the zero-step check was skipped.
Python's range() then raised a bare ValueError rather than a
library FunctionCallError.

$random(boundary=0)

$random(0)   # returned a random float in [0, 1) — should always be 0

boundary=0 evaluated as falsy, so the function ignored it and returned
random.random() instead of random.randint(0, 0) = 0.

Fix

Replace if stop: / if step: / if boundary: with is not None
comparisons in lib/rule_engine/builtins.py. Add regression tests for
$range(5, 0) and $random(0).

---

This pull request was prepared with the assistance of AI, under my direction and review.

[zeroSteiner]

Yup, that looks legit. Thanks for reporting and submitting a fix for this.

[zeroSteiner]

LGTM

(rule-engine)   : rule-engine: 13:07:05 madcat rule-engine PYTHONPATH=$(pwd)/lib python -m rule_engine.debug_repl
rule > $range(0)
result: 
()
rule > $range(5, 0)
result: 
(Decimal('0'), Decimal('1'), Decimal('2'), Decimal('3'), Decimal('4'))
rule > $random(0)
result: 
Decimal('0.2432948731525687')
rule >                                                                                                                                                                                                             
(rule-engine)   : rule-engine: 13:07:57 madcat rule-engine git checkout-pr 118
remote: Enumerating objects: 7, done.
remote: Counting objects: 100% (7/7), done.
remote: Total 7 (delta 5), reused 7 (delta 5), pack-reused 0 (from 0)
Unpacking objects: 100% (7/7), 1.30 KiB | 1.30 MiB/s, done.
From github:zeroSteiner/rule-engine
 * [new ref]         refs/pull/118/head -> pr/118
Switched to branch 'pr/118'
(rule-engine)   : rule-engine: 11813:08:01 madcat rule-engine PYTHONPATH=$(pwd)/lib python -m rule_engine.debug_repl
rule > $range(0)
result: 
()
rule > $range(5, 0)
result: 
()
rule > $random(0)
result: 
Decimal('0')
rule >

[zeroSteiner]

Patch shipped in 5.0.1. Thanks again.