cannot generate mockfile for generic type #271

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1. JuanBC9 commented on Oct 24, 2025

   

   JuanBC9

   on Oct 24, 2025

   Last edited by JuanBC9

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   Hi, adding (what I think is) a related finding to this issue.

   I've found that when using direct embedding of an instantiated generic (e.g., Base[MyStruct]). Mockgen generates syntactically incorrect code by using the fully qualified package path for the type argument, instead of the local type.

   Example:

   package mypackage
   
   // A generic function type
   type Callback[T any] func(item T)
   
   // A generic base interface
   type Base[T any] interface {
       OnEvent(callback Callback[T])
   }
   
   // A concrete struct
   type MyStruct struct {
   }
   
   // The interface to be mocked
   type MyInterface interface {
       Base[MyStruct]
   }

   mockgen "-destination" "mypackage/my_interface.go" "-package" "mypackage" -- "github.com/org/repo/mypackage" "MyInterface"

   Error: Failed to format generated source code: mypackage/my_interface.go missing ',' in type argument list

   Generated Code:

   // Uses the fully qualified path, which is a syntax error
   func (m *MockMyInterface) OnEvent(arg0 Callback[github.com/org/repo/mypackage.MyStruct]) {
   	m.ctrl.T.Helper()
   	m.ctrl.Call(m, "OnEvent", arg0)
   }

   Expected::

   // Should use the local type name
   func (m *MockMyInterface) OnEvent(arg0 Callback[MyStruct]) {
   	m.ctrl.T.Helper()
   	m.ctrl.Call(m, "OnEvent", arg0)
   }

   • golang version: 1.25.2
   • gomock version: v0.6.0

   👍React with 👍3Reacted by Ivan Ribakov, Víctor Arzoz and Meena Alfons
2. Bobrovskii commented on Oct 14, 2026

   

   Bobrovskii

   on Oct 14, 2026

   Last edited by Bobrovskii

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   I've opened #326 to fix the original source-mode issue. The PR resolves embedded interface aliases and adds regression tests for the parser and generated mocks.
   I also verified the package-mode example from #271 (comment). Mock generation and compilation already succeed for that example on current main