assert.Equal panic on diff unexported map with array as key

[olitez]

Description

assert.Equal could panic in some cases:

1. values must be same type but not equal
2. type must be struct with unexported field
3. field must be map with array as keys
4. map must have at least 2 values

Step To Reproduce

type test struct {
	m map[[1]byte]*struct{}
}

a := test{
	map[[1]byte]*struct{}{
		{1}: nil,
		{2}: nil,
	},
}
b := test{}

assert.Equal(t, a, b)

https://go.dev/play/p/1tziFuRiCw4

Expected behavior

show diff

Actual behavior

--- FAIL: TestTest (0.00s)
panic: reflect.Value.Interface: cannot return value obtained from unexported field or method [recovered]
	panic: reflect.Value.Interface: cannot return value obtained from unexported field or method

It fails on diff when trying to obtain dump from davecgh/go-spew, it's long time no updates nor fixes so probably worth to switch on something like yassinebenaid/godump

[dolmen]

👎 for replacing go-spew by another dependency.

Testify has a major place in the Go ecosystem, so we have strong responsibilities regarding our dependency chain. Adding a new dependency would have a significant impact on dependents.

[olitez]

Hi @dolmen

Thanks for your opinion! I agree that adding a dependency is not best scenario (not only for testify but mostly everywhere), but having existed dependency that panic on normal case is not very good for ecosystem imho.
If testify is really relying on go-spew maybe it worth to fork it and continue maintain under testify maintainers? This exact bug is just about single line fix add reflect.CanInterface before trying to reflect.Interface

[HaraldNordgren]

@olitez @dolmen Potential fix, although maybe we want to generalize it more? It there are broaded trend of failure cases?

#1816

[olitez]

@HaraldNordgren

thanks for fix, not showing actual diff but at least no panic

       	Error:      	Not equal:
       	            	expected: query.test{m:map[[1]uint8]string{[1]uint8{0x1}:"one", [1]uint8{0x2}:"two"}}
       	            	actual  : query.test{m:map[[1]uint8]string(nil)}
       	            	
       	            	Diff:
       	Test:       	TestXxx

I believe it could be some more cases when panic on diff but I'm not so familiar with go-spew so can't tell it exactly
I will probably take a look later on go-spew to find some more general cases

Close this one, if I will find something else will open new one

[brackendawson]

The change is not merged so I doubt this is fixed.