[JENKINS-32925] Add tracking to prevent stack overflows

[kwhetstone]

JENKINS-32925

To prevent stack overflows, especially in the Multiple SCMs case, track the subtypes to make sure the type isn't trying to discover itself. When that case is detected, don't log, and return back up the stack. This will only prevent duplication vertically, not horizontally.

@reviewbybees esp @jglick & @abayer

[ghost]

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[abayer]

Oooo, nicely done. 🐝

[jglick]

🐛 should be private

[jglick]

Good enough for the short term: addresses the stack overflow by simply omitting a legitimate choice. Later, if needed, we can introduce a new parameter type like Error which explicitly indicates recursion (or even a horizontal backreference), but that would require changes to the content generators too.

[jglick]

BTW there is an open issue for this on issues.jenkins-ci.org, assigned to you IIRC; link to it please.

[jglick]

Or more simply, pass new Stack<String>() as the argument in line 166.

[kwhetstone]

Added the @Nonnull annotation to the Stack in the constructor. I really like that annotation.

[kwhetstone]

Thanks for the reviews. I wanted to make a fairly minimal change so there wouldn't be that huge disruption to all the content generators. I definitely will keep introducing the error type in the back of my mind if this ends up being needed down the road.

[jglick]

🐝

[kohsuke]

While studying this fix, I noticed that this change missed the use of of in ArrayType instantiation here so the stack overflow continues with multiple-scm plugin.

The recursive portion of the stack is as follows (as of c85a422):

    at org.jenkinsci.plugins.workflow.structs.DescribableHelper$Schema.<init>(DescribableHelper.java:179)
    at org.jenkinsci.plugins.workflow.structs.DescribableHelper.schemaFor(DescribableHelper.java:152)
    at org.jenkinsci.plugins.workflow.structs.DescribableHelper.access$400(DescribableHelper.java:77)
    at org.jenkinsci.plugins.workflow.structs.DescribableHelper$ParameterType.of(DescribableHelper.java:344)
    at org.jenkinsci.plugins.workflow.structs.DescribableHelper$ParameterType.of(DescribableHelper.java:298)
    at org.jenkinsci.plugins.workflow.structs.DescribableHelper$ParameterType.of(DescribableHelper.java:369)
    at org.jenkinsci.plugins.workflow.structs.DescribableHelper$ParameterType.access$200(DescribableHelper.java:285)
    at org.jenkinsci.plugins.workflow.structs.DescribableHelper$Schema.<init>(DescribableHelper.java:179)

[jglick]

Probably better to leave a comment in jenkinsci/structs-plugin#1 requesting a test case be added that has something like Impl3 but whose polymorphic attribute is of type Base[].