Bug: mergo fails merge properly when it comes to map of struct

[iamhopaul123]

package main

import (
	"fmt"
	"github.com/imdario/mergo"
)

type Foo struct {
	A string
	B map[string]Bar
}

type Bar struct {
	C *string
	D *string
}

func main() {
	s1 := "asd"
	s2 := "sdf"
	src := Foo{
		A: "one",
		B: map[string]Bar{
			"foo": {
				D: &s2,
			},
		},
	}
	dest := Foo{
		A: "two",
		B: map[string]Bar{
			"foo": {
				C: &s1,
			},
		},
	}
	mergo.Merge(&dest, src, mergo.WithOverride, mergo.WithOverwriteWithEmptyValue)
	fmt.Println(dest.B["foo"])
}

Ideally it should output something like &{0xc000010250 0xc000010260}. However, the real output is {0xc000010250 <nil>}, which means that D: &s2 is ignored and not merged to dest.

The only work around is to make it pointer of struct like the following:

package main

import (
	"fmt"
	"github.com/imdario/mergo"
)

type Foo struct {
	A string
	B map[string]*Bar
}

type Bar struct {
	C *string
	D *string
}

func main() {
	s1 := "asd"
	s2 := "sdf"
	src := Foo{
		A: "one",
		B: map[string]*Bar{
			"foo": {
				D: &s2,
			},
		},
	}
	dest := Foo{
		A: "two",
		B: map[string]*Bar{
			"foo": {
				C: &s1,
			},
		},
	}
	mergo.Merge(&dest, src, mergo.WithOverride, mergo.WithOverwriteWithEmptyValue)
	fmt.Println(dest.B["foo"])
}

And the output is &{0xc000010250 0xc000010260} which is expected.

[darccio]

Resolved by reverting PR #105