Venkatesh-Prasad Ranganath created GROOVY-8537:
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Summary: GroovyCollections.combinations(Iterable) exhibits
incorrect asymmetric behavior
Key: GROOVY-8537
URL: https://issues.apache.org/jira/browse/GROOVY-8537
Project: Groovy
Issue Type: Bug
Components: groovy-jdk
Affects Versions: 2.4.15
Reporter: Venkatesh-Prasad Ranganath
h4. *Issue*
When GroovyCollections.combinations() is invoked on a collection of iterables
with at least one empty iterable, the expected return value is an empty list of
combinations.
Instead, in version 2.4.15 (and I am guessing in earlier versions at least
since 2.2.0), the return value of combinations() is sensitive to the order of
iterables in the input collection. Here are two instances of such behavior.
h4. Repro
{{groovy:000> assert [[1,3], []].combinations() == [[], [1,3]].combinations()}}
{{ERROR org.codehaus.groovy.runtime.powerassert.PowerAssertionError:}}
{{assert [[1,3], []].combinations() == [[], [1,3]].combinations()}}
{{ | | |}}
{{ [] false [[1], [3]]}}
{{groovy:000> assert [[1,3], [2], []].combinations() == [[1,3], [],
[2]].combinations()}}
{{ERROR org.codehaus.groovy.runtime.powerassert.PowerAssertionError:}}
{{assert [[1,3], [2], []].combinations() == [[1,3], [], [2]].combinations()}}
{{ | | |}}
{{ [] false [[2]]}}
h4. *Fix*
A simple short-circuiting check at the start of combinations(Iterable) method
to return an empty list of combination if any of the input iterables are empty
should fix the problem.
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