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https://issues.apache.org/jira/browse/GROOVY-10856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17641975#comment-17641975
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Eric Milles edited comment on GROOVY-10856 at 12/1/22 2:41 PM:
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-I think the guarantee of "never throw an exception" states that groovy will
not throw an exception in locating or invoking the method. If the method
throws an exception internally, that is another matter. [~paulk] can probably
clarify better than I can.-
Update: Sorry, I misunderstood. {{respondsTo}} is not supposed to throw and
you are saying it is throwing {{MethodSelectionException}}, correct?
We could strive for additional checking that if an argument matches a named
parameter collector (a Map with {{@NamedParam}} metadata) that the required
names and types are supplied. In your example, if you call
{{respondsTo('myMethod', [name: ''])}} does it give an empty list due to the
missing "number" element?
was (Author: emilles):
I think the guarantee of "never throw an exception" states that groovy will not
throw an exception in locating or invoking the method. If the method throws an
exception internally, that is another matter. [~paulk] can probably clarify
better than I can.
We could strive for additional checking that if an argument matches a named
parameter collector (a Map with {{@NamedParam}} metadata) that the required
names and types are supplied. In your example, if you call
{{respondsTo('myMethod', [name: ''])}} does it give an empty list due to the
missing "number" element?
> MethodSelectionException when calling respondsTo()
> --------------------------------------------------
>
> Key: GROOVY-10856
> URL: https://issues.apache.org/jira/browse/GROOVY-10856
> Project: Groovy
> Issue Type: Bug
> Components: Documentation
> Affects Versions: 4.0.6
> Environment: Seen in Groovy 4.0.6 on Linux x64 with java 17.0.5 and
> MacOS aarch64 in Java 19.0.1. I don't think any of that is significant. 😀
> Reporter: Rachel Greenham
> Priority: Minor
> Attachments: responds-to-issue.groovy
>
>
> if you have a method which takes certain parameters, and annotate itÂ
> {{@NamedVariant}}, and then try a {{respondsTo}} with a null, or an empty
> array, you get this exception, listing both the methods that are there,
> rather than the expected groovy-falsehood (empty list) for no matching
> methods.
> This is related toÂ
> # GROOVY-8248
> # GROOVY-8660
> but is different in scope because this is about the behaviour, specifically,
> of MetaObjectProtocol::respondsTo, which states clearly in the documentation
> that:
> {quote}This method is "safe" in that it will always return a value and never
> throw an exception
> {quote}
> ... which turns out not to be true, and should be. The behaviour may not be
> wrong for the calls described in the other two bugs, but
> {{MetaObjectProtocol::respondsTo}}, specifically, should be catching this,
> and returning, as promised, a groovy falsehood. (probably an empty list,
> which is correct as neither of the methods match.)
> Attached, a small script demonstrating this, which shows the problem clearly
> if simply run in groovy console.
> {code:groovy}
> import groovy.transform.*
> @NamedVariant
> def myMethod(int number, String name) {
> println "number: ${number}; name: ${name}"
> }
> println myMethod(42, 'Arthur')
> println myMethod(name: 'Arthur', number: 42)
> def result1 = respondsTo('myMethod', 42, 'Arthur')
> println "positive match: ${result1}"
> def result2 = respondsTo('myMethod', [number: 42, name: 'Arthur'])
> println "positive match: ${result2}"
> def result3 = respondsTo('myMethod', null)
> // expected an empty list, a groovy-falsehood
> {code}
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