Sorting a list on three properties

[terse ridge]

I am using a comparator to sort a list based on three properties. I want entries to be at the end of the list if any of the following conditions are true

isNullable == true
required == false
defaultValue != null

This stub works in most cases, but I was informed of an edge case were we get error Comparison method violates its general contract! How can I fix it?

    public static Comparator<CodegenProperty> propertyComparatorByNotNullableRequiredNoDefault = new Comparator<CodegenProperty>() {
        @Override
        public int compare(CodegenProperty one, CodegenProperty another) {
            if (one.isNullable == another.isNullable && one.required == another.required && (one.defaultValue == null) == (another.defaultValue == null))
                return 0;
            else if (!one.isNullable && one.required && one.defaultValue == null)
                return -1;
            else
                return 1;
        }
    };

[gilded hinge]

<@&987246399047479336> please have a look, thanks.

[exotic nacelle]

what about:

Comparator.comparing(property -> property.isNullable) // might need custom keyComparator
    .thenComparing(property -> property.required) // might need custom keyComparator
    .thenComparing(property -> property.defaultValue, Comparator.nullsLast(...));

something like this

but I am not sure how the default boolean keyComparator works

let me do some testing so I can tell for sure

[terse ridge]

Thanks a lot. I just tried this, and it works, but changes a bit more than I was hoping for.

    public static Comparator<CodegenProperty> propertyComparatorByNotNullableRequiredNoDefault = new Comparator<CodegenProperty>() {
        @Override
        public int compare(CodegenProperty one, CodegenProperty another) {
            if (one.isNullable == another.isNullable && one.required == another.required && (one.defaultValue == null) == (another.defaultValue == null))
                return 0;
            else if ((!one.isNullable && another.isNullable) || (one.required && !another.required) || (one.defaultValue == null && another.defaultValue != null))
                return -1;
            else
                return 1;
        }
    };

[exotic nacelle]

ok this should actually work:

Comparator.comparing(p -> p.isNullable)
    .thenComparing(p -> !p.required)
    .thenComparing(p -> p.defaultValue != null);

[terse ridge]

This works for the edge case and without changing much of what I already have.

    public static Comparator<CodegenProperty> propertyComparatorByNotNullableRequiredNoDefault = new Comparator<CodegenProperty>() {
        @Override
        public int compare(CodegenProperty one, CodegenProperty another) {
            if (one.isNullable == another.isNullable && one.required == another.required && (one.defaultValue == null) == (another.defaultValue == null))
                return 0;
            else if (!one.isNullable && one.required && one.defaultValue == null)
                return -1;
            else
                return one.name.compareTo(another.name);
        }
    };

[exotic nacelle]

but only if you want it in that order

[terse ridge]

Same as the original code but the else compares the name.

[exotic nacelle]

ok yea my solution does smth slightly different

[terse ridge]

Okay, thank you for your help!

I take it back, my change doesn't quite work. How do I get your version in here?

[exotic nacelle]

well my version wont work as expected lol

[exotic nacelle]

because this compares in order

iirc

it only checks the second value if the first are equal

and you didnt state if thats what you want

so idk

[terse ridge]

I think it will work.

[exotic nacelle]

can you share CodegenProperty

[terse ridge]

It's a huge class.

[exotic nacelle]

well I cant tell you whats wrong with this if I dont know the class

[terse ridge]

https://github.com/OpenAPITools/openapi-generator/blob/ef0d10df8d57b3dcd11d66a87f8214e9c3c081c3/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java#L26

[exotic nacelle]

hm maybe it doesnt register the generics

maybe try this:

Comparator.<CodegenProperty, Boolean>comparing(p -> p.isNullable)
    .thenComparing(p -> !p.required)
    .thenComparing(p -> p.defaultValue != null);

[terse ridge]

Okay, that runs. Let me study it to see if it is the right output.

[exotic nacelle]

I am wondering why it doesnt detect the generics automatically

well I think you can even use this shorter version:

Comparator.comparing((CodegenProperty p) -> p.isNullable)
    .thenComparing(p -> !p.required)
    .thenComparing(p -> p.defaultValue != null);

[exotic nacelle]

tested it and generic type inference by using target types works for me 🤷‍♂️

[terse ridge]

Looks like this is what I want

   public static Comparator<CodegenProperty> propertyComparatorByNotNullableRequiredNoDefault =
            Comparator.comparing(p -> p.isNullable || !p.required || p.defaultValue != null);

[exotic nacelle]

I wouldnt be too sure

now if the first element is null and the second element got required = false, then they both evaluate to true and be equal

[terse ridge]

I think that is okay. If any of my three conditions stated above are true, then it should be at the end. Looks like that is what happens.

[exotic nacelle]

ah ok, if thats what you want

[terse ridge]

Yes, this is generating C# code. The constructor requires that parameters with a default value be at the end of the signature.

[exotic nacelle]

using java to generate c# code lol

thats interesting

[terse ridge]

It uses mustache templates to generate any language you like.