mockery fails to generate mocks for interfaces that use generics

[LandonTClipp]

Description

This is a meta ticket to track issues with 1.18 generics.

#442
#439

Version

2.11.0

[Gevrai]

I'd be interested in taking a crack at this issue, if no one else is.

It means bumping the project to go 1.18 though, do you foresee any issue with this? It means that anyone compiling from source would need to have go 1.18 compiler I think.

[LandonTClipp]

Thanks for volunteering @Gevrai . I have been debating this internally, supporting generics is a backwards-incompatible change since we'd need to bump to go 1.18 as you mentioned. However, I have been pushing people to not go install mockery as it becomes dependent on the version of mockery installed and thus would fail if the project uses a language feature from a version they don't have installed. Downloading from the pre-built binaries is the best option.

There might be a way around this with build tags. I am wondering if we can exclude certain golang files based on the version of golang used for building?

[cruickshankpg]

Sorry @Gevrai I missed your comment and made my own attempt at this

[AntonioYuen]

+1

[Gevrai]

Sorry @Gevrai I missed your comment and made my own attempt at this

Hey no worries !

If that might be of any help, I tried to figure out an interface which should cover all potential issues that would arise with generating mocks for a Generic interface with odd constraints. It might be valuable to split into many interfaces instead though 😅

I might have missed some cases as well.

type RequesterGenerics[
	TAny any,
	TComparable comparable,
	TSigned constraints.Signed, // external constraint
	TIntf GetInt, // internal interface
	TExternalIntf io.Writer, // external interface
	TGenIntf GetGeneric[TSigned], // generic interface
	TInlineType interface{ ~int | ~uint }, // inlined interface constraints
	TInlineTypeGeneric interface {
		~int | GenericType[int, GetInt]
	}, // inlined type constraints
	TInlineIntf interface{ Get() int }, // inlined interface definition
] interface {
	GenericArguments(TAny, TComparable) (TSigned, TIntf)
	GenericStructs(GenericType[TAny, TIntf]) GenericType[TSigned, TIntf]
	GenericStructsSpecificType(GenericType[int, TInlineIntf]) GenericType[TInlineType, interface{ Get() int }]
	GenericStructsMix(GenericType[string, GetGeneric[int]]) GenericType[int, TInlineIntf]
	GenericAnonymousStructs(struct{ Type1 TExternalIntf }) struct {
		Type2 GenericType[string, EmbeddedGet[int]]
	}
}

type GenericType[T any, S GetInt] struct {
	Any  T
	Some []S
}

type GetInt interface{ Get() int }

type GetGeneric[T constraints.Integer] interface{ Get() T }

type EmbeddedGet[T constraints.Signed] interface{ GetGeneric[T] }

[cruickshankpg]

That's a more complete set than I was using and have moved my tests to use it thanks. I had missed union types and embedded generic types with type arguments and have now added support.

I have dropped the inlined interfaces with methods though as mockery does not currently support them and I think that's a separate line of work to this.