Function ExampleOption_equalEmpty

cmp/example_test.go:163–190

Sometimes, an empty map or slice is considered equal to an allocated one of zero length. This example is for demonstrative purposes; use [github.com/google/go-cmp/cmp/cmpopts.EquateEmpty] instead.

()

// This example is for demonstrative purposes;
// use [github.com/google/go-cmp/cmp/cmpopts.EquateEmpty] instead.
func ExampleOption_equalEmpty() {
	alwaysEqual := cmp.Comparer(func(_, _ interface{}) bool { return true })

	// This option handles slices and maps of any type.
	opt := cmp.FilterValues(func(x, y interface{}) bool {
		vx, vy := reflect.ValueOf(x), reflect.ValueOf(y)
		return (vx.IsValid() && vy.IsValid() && vx.Type() == vy.Type()) &&
			(vx.Kind() == reflect.Slice || vx.Kind() == reflect.Map) &&
			(vx.Len() == 0 && vy.Len() == 0)
	}, alwaysEqual)

	type S struct {
		A []int
		B map[string]bool
	}
	x := S{nil, make(map[string]bool, 100)}
	y := S{make([]int, 0, 200), nil}
	z := S{[]int{0}, nil} // []int has a single element (i.e., not empty)

	fmt.Println(cmp.Equal(x, y, opt))
	fmt.Println(cmp.Equal(y, z, opt))
	fmt.Println(cmp.Equal(z, x, opt))

	// Output:
	// true
	// false
	// false
}

// Two slices may be considered equal if they have the same elements,
// regardless of the order that they appear in. Transformations can be used