palantir / palantir/palantir-java-format

Poor formatting of generic parameters on methods when class names are long

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Dominant language
Java
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Description

What happened?

We encountered a class in our codebase with a generic parameter T on one of its methods. T has bounds that involve classes with long names, and when we format this class with Palantir format, we get the following:

public class CrazyGenerics {

    public <
                    T extends
                            FantasticVeryLongNamedContainerWithLongName<?, ?, ?, ?>
                                    & OtherLongNamedTypeWithOnlyOneGenericType<?>>
            void computeInfo() {}

    public interface FantasticVeryLongNamedContainerWithLongName<FirstType, SecondType, ThirdType, FourthType> {
        FirstType getFirst();

        SecondType getSecond();

        ThirdType getThird();

        FourthType getFourth();
    }

    public interface OtherLongNamedTypeWithOnlyOneGenericType<FirstType> {
        FirstType getFirst();
    }
}

What did you want to happen?

I could see a few better alternatives.

Be consistent with the indentation after methods:

    public <
            T extends
                    FantasticVeryLongNamedContainerWithLongName<?, ?, ?, ?>
                            & OtherLongNamedTypeWithOnlyOneGenericType<?>>
            void computeInfo() {}

Or perhaps leave the generic type on the original line:

    public <T extends
            FantasticVeryLongNamedContainerWithLongName<?, ?, ?, ?>
                    & OtherLongNamedTypeWithOnlyOneGenericType<?>>
            void computeInfo() {}

Other suggestions welcome, but I hope it's clear why the original is not ideal.

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Research direction

No source file or test is named. Begin by reproducing the long generic method example with Palantir Java Format, then trace the formatter entry point responsible for method type-parameter layout and add a regression check matching the preferred indentation once the expected alternative is chosen.

Written by the indexing model from the issue text.

Assessment

Tech stack
java
Domain
tooling
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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