panic: reflect: reflect.Value.Set using unaddressable value merging nested structures #90
Description
Hi,
I want to do a deep merge where non-empty dst attributes are overwritten with non-empty src attributes values but slices are appended, is this possible?
Can someone help me understand why this does't work?
package main
import (
"fmt"
"github.com/imdario/mergo"
)
type My struct {
Name string
Data []int
Other map[string]Other
}
type Other struct {
Foo string
Bar int
Baz []string
Faz map[string]string
}
func main() {
dst := My{
Data: []int{1, 2, 3},
Name: "Dest",
Other: map[string]Other{
"stuff": Other{
Foo: "bar",
Bar: 0,
},
},
}
new := My{
Data: []int{4, 5},
Name: "Source",
Other: map[string]Other{
"stuff": Other{
Foo: "bar",
Bar: 1,
},
"Morestuff": Other{
Foo: "foo",
Bar: 2,
},
},
}
new2 := My{
Name: "Source2",
Other: map[string]Other{
"stuff": Other{
Foo: "bar",
Bar: 1,
},
"Morestuff": Other{
Foo: "foo",
Bar: 2,
Baz: []string{"something", "wrong"},
Faz: map[string]string{
"some": "some2",
},
},
},
}
fmt.Println(dst)
fmt.Println(new)
fmt.Println(new2)
mergo.Merge(&dst, &new, mergo.WithAppendSlice, mergo.WithOverride)
fmt.Println(dst)
mergo.Merge(&dst, &new2, mergo.WithAppendSlice, mergo.WithOverride)
fmt.Println(dst)
}
I get:
$ go run test.go
{Dest [1 2 3] map[stuff:{bar 0 [] map[]}]}
{Source [4 5] map[Morestuff:{foo 2 [] map[]} stuff:{bar 1 [] map[]}]}
{Source2 [] map[stuff:{bar 1 [] map[]} Morestuff:{foo 2 [something wrong] map[some:some2]}]}
{Source [1 2 3 4 5] map[Morestuff:{foo 2 [] map[]} stuff:{bar 1 [] map[]}]}
panic: reflect: reflect.Value.Set using unaddressable value
goroutine 1 [running]:
reflect.flag.mustBeAssignable(0x95)
/usr/local/Cellar/go/1.11.1/libexec/src/reflect/value.go:234 +0x157
reflect.Value.Set(0x10b0760, 0xc000022470, 0x95, 0x10b0760, 0xc000074480, 0x15)
/usr/local/Cellar/go/1.11.1/libexec/src/reflect/value.go:1397 +0x2f
github.com/imdario/mergo.deepMerge(0x10b0760, 0xc000022470, 0x95, 0x10b0760, 0xc000022430, 0x95, 0xc000095b08, 0x3, 0xc00000a1c0, 0x0, ...)
/Users/ldavim/go/src/github.com/imdario/mergo/merge.go:83 +0x1388
github.com/imdario/mergo.deepMerge(0x10bcde0, 0xc000022440, 0x99, 0x10bcde0, 0xc000022400, 0x99, 0xc000095b08, 0x2, 0xc00000a1c0, 0x0, ...)
/Users/ldavim/go/src/github.com/imdario/mergo/merge.go:72 +0x23a7
github.com/imdario/mergo.deepMerge(0x10b0700, 0xc0000741a8, 0x195, 0x10b0700, 0xc000074268, 0x195, 0xc000095b08, 0x1, 0xc00000a1c0, 0x0, ...)
/Users/ldavim/go/src/github.com/imdario/mergo/merge.go:115 +0x986
github.com/imdario/mergo.deepMerge(0x10b9ba0, 0xc000074180, 0x199, 0x10b9ba0, 0xc000074240, 0x199, 0xc000095b08, 0x0, 0xc00000a1c0, 0x199, ...)
/Users/ldavim/go/src/github.com/imdario/mergo/merge.go:72 +0x23a7
github.com/imdario/mergo.merge(0x10a4780, 0xc000074180, 0x10a4780, 0xc000074240, 0xc000095ce8, 0x2, 0x2, 0x0, 0x0)
/Users/ldavim/go/src/github.com/imdario/mergo/merge.go:251 +0x29f
github.com/imdario/mergo.Merge(0x10a4780, 0xc000074180, 0x10a4780, 0xc000074240, 0xc000095ce8, 0x2, 0x2, 0x0, 0x0)
/Users/ldavim/go/src/github.com/imdario/mergo/merge.go:206 +0x71
main.main()
/Users/ldavim/Desktop/test.go:72 +0xa28
exit status 2
So, the first merge works but the second one fails.
Thanks