If a matcher panics and AssertExpectations has been deferred, a hang occurs

[cchalm]

In the code below, the test case TestMatcherPanic hangs. To reproduce the hang, two conditions must be met:

1. AssertExpectations is deferred
2. An argument matcher panics

import (
	"testing"

	"github.com/stretchr/testify/mock"
)

type Mock struct {
	mock.Mock
}

func (_m *Mock) F() {
	_m.Called()
}

func TestMatcherPanic(t *testing.T) {
  m := &Mock{}
  defer m.AssertExpectations(t)

  matcher := mock.MatchedBy(func(_ interface{}) bool {
    panic("test")
  })
  m.On("F", matcher)

  m.F()
}

[brackendawson]

I think this is because the Called() ends up locking a mutex here, then the panic goes unhandled, then the deferred AssertExpectations() runs and tried to lock the same mutex here.

Basically this is happening:

package main

import "sync"

func main() {
	m := sync.Mutex{}
	defer func() { m.Lock() }()
	m.Lock()
	panic("oh no")
	m.Unlock()
}

I think this call needs to be wrapped in a function with a deferred recovery that unlocks the mutex and delares the function call unexpected because panic "blah" occurred.

[cfiderer]

This also happens when a nil argument is matched against an AnythingOfTypeArgument expectation: the internal panic is not handled, the test unwinds (with m.mutex already locked), and AssertExpectations() tries to lock m.mutex again.