any matcher and creating matchers for structures

[godolatry]

I see that pegomock has specific matchers for strings and other basic objects, but I can't see an "any" matcher. Have I missed something?

Also, when I create my own structures, is it possible to use matchers for them?

[petergtz]

Since Go does not have generics, it's not possible to write a generic Any matcher. The matcher must return a proper type. It cannot just return interface{}, because that wouldn't satisfy the mocks function signature.

You should be able to create your own matchers very easily though. Have a look at matcher_factories.go. I think something like this should work:

func AnyMyType() MyType {
    RegisterMatcher(&matcher.AnyMatcher{Type: reflect.Struct})
    return MyType{}
}

I think at some point I will add the auto-generation of some default matchers based on the types used in the interface signatures for which a mock is generated. For the time being, they must be added manually though.

Hope this helps.

[godolatry]

Or do you mean:

func AnyMyType() MyType {
RegisterMatcher(&matcher.AnyMatcher{Type: reflect.Struct})
return nil
}

which follows the style of the existing "Any..." matchers - they all
seem to return an appropriate zero value.

Question is, where do I put this function?

matcher is an internal package so I can't import it into my code. This
means that I can't add the method shown above to my test module.

As far as I can see, I would have to hack the pegomock code that I have
downloaded and add my matcher method there, which seems like a bad idea.

Am I missing something obvious?

On Sat, Sep 3, 2016 at 8:32 PM, Peter Götz notifications@github.com wrote:

Since Go does not have generics, it's not possible to write a generic Any
matcher. The matcher must return a proper type. It cannot just return
interface{}, because that wouldn't satisfy the mocks function signature.

You should be able to create your own matchers very easily though. Have a
look at matcher_factories.go. I think something like this should work:

func AnyMyType() MyType {
RegisterMatcher(&matcher.AnyMatcher{Type: reflect.Struct})
return MyType{}
}

I think at some point I will add the auto-generation of some default
matchers based on the types used in the interface signatures for which a
mock is generated. For the time being, they must be added manually though.

Hope this helps.

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[petergtz]

The zero value for MyType is MyType{}. nil can only be used for pointer types, i.e. *MyType. So it depends on the method signature in your interface.

You're right that matcher is not visible outside. That's a bug. I will try to fix it soon, but feel free to provide a pull request, if you need it now.

Thanks.

[petergtz]

@godolatry Does this solve your issue?

[godolatry]

I'm away at present. I will try this tomorrow (Friday)

Thanks and Regards

Simon

On Wednesday, September 7, 2016, Peter Götz notifications@github.com
wrote:

@godolatry https://github.com/godolatry Does this solve your issue?

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[goblimey]

That seems to work, but it only allows me to create a matcher for one of my own own structures. This is because of the "reflect.Struct" part:
func AnyMyType() MyType {
pegomock.RegisterMatcher(&matcher.AnyMatcher{Type: reflect.Struct})
return MyType{}
}

I also need to create a matcher for an interface type.

For example, assume I have defined interfaces A and B plus a structure C. I have objects of those types called a, b and c. Both a and b are mocks. My application makes this call:

a.fun(b, c)

If I need to write a WHEN that uses a matcher for c, then I must supply matchers for all of the parameters, so I need something like:

pegomock.When(a.fun(EqB(b), EqC(c)))

So I need to create a matcher for b, which is an interface with a mock behind it.

Is that possible?

[petergtz]

Hi @goblimey,

Can you try with reflect.Interface instead of reflect.Struct when MyType is an interface? Something like this:

func AnyMyType() MyType {
    pegomock.RegisterMatcher(&matcher.AnyMatcher{Type: reflect.Interface})
    return MyType{}
}

I will try this out myself as soon as possible, but maybe it already solves your problem.

[petergtz]

@goblimey, @godolatry (you are both called Simon. Are you the same person actually?)

I've just pushed a change which will now properly support custom any-matchers based on interface types.

E.g. if you want to write a custom matcher for the error interface, you would do it like this:

func AnyError() error {
    RegisterMatcher(NewAnyMatcher(reflect.TypeOf((*error)(nil)).Elem()))
    return nil
}

The TypeOf construct looks a bit convoluted, but it's the recommended way.

Let me know if this solves your issue. Thanks.

[petergtz]

@goblimey, @godolatry I'm closing this issue due to inactivity. Feel free to re-open, if you don't think the issue is solved.