Compare(map, uninitialised map) returns no output

[kylelemons]

Compare(map, uninitialised map) returns no output

[kylelemons]

This is definitely the intended behavior. If you need to inequality
between things like this or zero/nil slices, you'll need something like
reflect.DeepEqual.

On Fri, Mar 20, 2015, 6:16 PM Mihai [email protected] wrote:

var xs struct{
x, y map[string]string
}
xs.x = make(map[string]string)
xs.x = make(map[string]string)
fmt.Printf("%s", pretty.Compare(xs.x, xs.y)) // returns an empty string

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#3.

[themihai]

Debugging inequality on maps is not "pretty" thus the proposal to pretty print the diff between initialised and uninitialised maps.
Below is an example.

type Some struct{
Node *Some
 one map[string]string
    }
s := Some{}
s.one = make(map[string]string)
s1 := Some{}
if !reflect.DeepEqual(s, s1) {
    fmt.Printf("s %v, s1 %v", s, s1)
}

Prints

s {map[] map[]}, s1 {map[] map[]}

[kylelemons]

I believe the examples show that Compare(x, y) == "" is the intended way to
check rough equality. My intent is that semantically equivalent objects be
considered equal. Zeroed and nil slices, for instance, should work the
same in correctly-written code. Empty and nil maps should similarly be
indistinguishable in normal use.

On Mon, Mar 23, 2015, 12:41 PM Mihai [email protected] wrote:

I see… though if Compare reports the diff between initialised and nil maps
it would improve the debug experience. I actually use reflect.DeepEqual to
test the inequality and Compare to print the differences.(which I think
it's how Compare is intended to be used). However if you have structs with
maps there is no way to tell why the inequality fails without to
reflect.DeepEqual on each map field. Let me know if there is something I'm
missing.
Here is an example:

s := Some{}
s.one = make(map[string]string)
s1 := Some{}
if !reflect.DeepEqual(s, s1) {
fmt.Printf("s %v, s1 %v", s, s1)
}

Prints

s {map[] map[]}, s1 {map[] map[]}

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#3 (comment).

[voutasaurus]

While I agree that Compare is meant to be more coarse than reflect.DeepEqual, I think a "Why is reflect.DeepEqual returning false?" mode or function would be incredibly useful.

For instance reflect.DeepEqual says that non nil functions are never equal, even if they have the same pointer value. pretty.Compare will return nothing in this case. A pretty.DeepCompare function would instead point out that the objects contain functions.

Similarly with other things that are not DeepEqual.

[kylelemons]

Thanks for the suggestion, but I think this feature request runs counter to the goals of godebug; I would check out go-spew which might have the level of detail that you want.