Add spec for defined? on constant with const_missing

[richardboehme]

Make sure that defined? returns nil even if const_missing is implemented in the parent.

We noticed this while implementing defined? in Natalie (see natalie-lang/natalie#2289, natalie-lang/natalie#1734)

[andrykonchin]

The term parent is not accurate. It should be about outer scope/module/etc of a constant.

minor: it's common to prefix a method name with either . or # in a spec title so const_missing becomes . const_missing.

[andrykonchin]

Dynamic defining a new method in a class/module shared by multiple test cases may make them surprisingly coupled, what makes sense to avoid.

So I would add a new fixture module/class specifically for this test case, e.g. DefinedSpecs::ModuleWithConsMissing instead.

[richardboehme]

@andrykonchin Thanks for the review! Actually I've looked at the spec again and there are already tests to check that .const_missing is not being called. I guess the issue why the spec did not fail for us is on Natalie's part then.

The current tests use a should_not_receive expectation (see for example it "does not call .const_missing if the constant is not defined"). Do you see any value in adding a test that actually implements const_missing? Otherwise I think we can close this 😅

[andrykonchin]

Yeah, I would say it makes sense to add this test case. At least it would catch the issue in your case.

There might be a tiny difference between semantic of the new test and the existing one. Actually the #should_not_receive method does the same - it defines a new method and checks that it isn't called. But its implementation could be changed (e.g. with #method_missing).

[richardboehme]

Yeah, I would say it makes sense to add this test case. At least it would catch the issue in your case.

There might be a tiny difference between semantic of the new test and the existing one. Actually the #should_not_receive method does the same - it defines a new method and checks that it isn't called. But its implementation could be changed (e.g. with #method_missing).

Ok I've implemented the changes you requested, let me know if anything is missing!

[andrykonchin]

Thank you! Looks good.