README.md

@@ -8,8 +8,7 @@
 [![Coverage Status][9]][10]
 [![Sourcegraph][11]][12]
 [![FOSSA Status][13]][14]
-
-[![GoCenter Kudos][15]][16]
+[![Become my sponsor][15]][16]
 
 [1]: https://travis-ci.org/imdario/mergo.png
 [2]: https://travis-ci.org/imdario/mergo
@@ -25,8 +24,8 @@
 [12]: https://sourcegraph.com/github.com/imdario/mergo?badge
 [13]: https://app.fossa.io/api/projects/git%2Bgithub.com%2Fimdario%2Fmergo.svg?type=shield
 [14]: https://app.fossa.io/projects/git%2Bgithub.com%2Fimdario%2Fmergo?ref=badge_shield
-[15]: https://search.gocenter.io/api/ui/badge/github.com%2Fimdario%2Fmergo
-[16]: https://search.gocenter.io/github.com/imdario/mergo
+[15]: https://img.shields.io/github/sponsors/imdario
+[16]: https://github.com/sponsors/imdario
 
 A helper to merge structs and maps in Golang. Useful for configuration default values, avoiding messy if-statements.
 
@@ -36,11 +35,11 @@ Also a lovely [comune](http://en.wikipedia.org/wiki/Mergo) (municipality) in the
 
 ## Status
 
-It is ready for production use. [It is used in several projects by Docker, Google, The Linux Foundation, VMWare, Shopify, etc](https://github.com/imdario/mergo#mergo-in-the-wild).
+It is ready for production use. [It is used in several projects by Docker, Google, The Linux Foundation, VMWare, Shopify, Microsoft, etc](https://github.com/imdario/mergo#mergo-in-the-wild).
 
 ### Important note
 
-Please keep in mind that a problematic PR broke [0.3.9](//github.com/imdario/mergo/releases/tag/0.3.9). I reverted it in [0.3.10](//github.com/imdario/mergo/releases/tag/0.3.10), and I consider it stable but not bug-free. Also, this version adds suppot for go modules.
+Please keep in mind that a problematic PR broke [0.3.9](//github.com/imdario/mergo/releases/tag/0.3.9). I reverted it in [0.3.10](//github.com/imdario/mergo/releases/tag/0.3.10), and I consider it stable but not bug-free. Also, this version adds support for go modules.
 
 Keep in mind that in [0.3.2](//github.com/imdario/mergo/releases/tag/0.3.2), Mergo changed `Merge()`and `Map()` signatures to support [transformers](#transformers). I added an optional/variadic argument so that it won't break the existing code.
 
@@ -51,12 +50,12 @@ If you were using Mergo before April 6th, 2015, please check your project works
 If Mergo is useful to you, consider buying me a coffee, a beer, or making a monthly donation to allow me to keep building great free software. :heart_eyes:
 
 <a href='https://ko-fi.com/B0B58839' target='_blank'><img height='36' style='border:0px;height:36px;' src='https://az743702.vo.msecnd.net/cdn/kofi1.png?v=0' border='0' alt='Buy Me a Coffee at ko-fi.com' /></a>
-[![Beerpay](https://beerpay.io/imdario/mergo/badge.svg)](https://beerpay.io/imdario/mergo)
-[![Beerpay](https://beerpay.io/imdario/mergo/make-wish.svg)](https://beerpay.io/imdario/mergo)
 <a href="https://liberapay.com/dario/donate"><img alt="Donate using Liberapay" src="https://liberapay.com/assets/widgets/donate.svg"></a>
+<a href='https://github.com/sponsors/imdario' target='_blank'><img alt="Become my sponsor" src="https://img.shields.io/github/sponsors/imdario?style=for-the-badge" /></a>
 
 ### Mergo in the wild
 
+- [cli/cli](https://github.com/cli/cli)
 - [moby/moby](https://github.com/moby/moby)
 - [kubernetes/kubernetes](https://github.com/kubernetes/kubernetes)
 - [vmware/dispatch](https://github.com/vmware/dispatch)
@@ -98,6 +97,8 @@ If Mergo is useful to you, consider buying me a coffee, a beer, or making a mont
 - [jnuthong/item_search](https://github.com/jnuthong/item_search)
 - [bukalapak/snowboard](https://github.com/bukalapak/snowboard)
 - [containerssh/containerssh](https://github.com/containerssh/containerssh)
+- [goreleaser/goreleaser](https://github.com/goreleaser/goreleaser)
+- [tjpnz/structbot](https://github.com/tjpnz/structbot)
 
 ## Install
 
@@ -168,7 +169,7 @@ func main() {
 
 Note: if test are failing due missing package, please execute:
 
-    go get gopkg.in/yaml.v2
+    go get gopkg.in/yaml.v3
 
 ### Transformers
 
@@ -218,7 +219,6 @@ func main() {
 }
 ```
 
-
 ## Contact me
 
 If I can help you, you have an idea or you are using Mergo in your projects, don't hesitate to drop me a line (or a pull request): [@im_dario](https://twitter.com/im_dario)
@@ -227,18 +227,6 @@ If I can help you, you have an idea or you are using Mergo in your projects, don
 
 Written by [Dario Castañé](http://dario.im).
 
-## Top Contributors
-
-[![0](https://sourcerer.io/fame/imdario/imdario/mergo/images/0)](https://sourcerer.io/fame/imdario/imdario/mergo/links/0)
-[![1](https://sourcerer.io/fame/imdario/imdario/mergo/images/1)](https://sourcerer.io/fame/imdario/imdario/mergo/links/1)
-[![2](https://sourcerer.io/fame/imdario/imdario/mergo/images/2)](https://sourcerer.io/fame/imdario/imdario/mergo/links/2)
-[![3](https://sourcerer.io/fame/imdario/imdario/mergo/images/3)](https://sourcerer.io/fame/imdario/imdario/mergo/links/3)
-[![4](https://sourcerer.io/fame/imdario/imdario/mergo/images/4)](https://sourcerer.io/fame/imdario/imdario/mergo/links/4)
-[![5](https://sourcerer.io/fame/imdario/imdario/mergo/images/5)](https://sourcerer.io/fame/imdario/imdario/mergo/links/5)
-[![6](https://sourcerer.io/fame/imdario/imdario/mergo/images/6)](https://sourcerer.io/fame/imdario/imdario/mergo/links/6)
-[![7](https://sourcerer.io/fame/imdario/imdario/mergo/images/7)](https://sourcerer.io/fame/imdario/imdario/mergo/links/7)
-
-
 ## License
 
 [BSD 3-Clause](http://opensource.org/licenses/BSD-3-Clause) license, as [Go language](http://golang.org/LICENSE).

go.mod

@@ -2,4 +2,4 @@ module github.com/imdario/mergo
 
 go 1.13
 
-require gopkg.in/yaml.v2 v2.3.0
+require gopkg.in/yaml.v3 v3.0.0

go.sum

@@ -1,4 +1,4 @@
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.3.0 h1:clyUAQHOM3G0M3f5vQj7LuJrETvjVot3Z5el9nffUtU=
-gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.0 h1:hjy8E9ON/egN1tAYqKb61G10WtihqetD4sz2H+8nIeA=
+gopkg.in/yaml.v3 v3.0.0/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

issue209_test.go

@@ -0,0 +1,26 @@
+package mergo_test
+
+import (
+	"testing"
+
+	"github.com/imdario/mergo"
+)
+
+func TestIssue209(t *testing.T) {
+	dst := []string{"a", "b"}
+	src := []string{"c", "d"}
+
+	if err := mergo.Merge(&dst, src, mergo.WithAppendSlice); err != nil {
+		t.Error(err)
+	}
+
+	expected := []string{"a", "b", "c", "d"}
+	if len(dst) != len(expected) {
+		t.Errorf("arrays not equal length")
+	}
+	for i := range expected {
+		if dst[i] != expected[i] {
+			t.Errorf("array elements at %d are not equal", i)
+		}
+	}
+}

merge.go

@@ -79,7 +79,7 @@ func deepMerge(dst, src reflect.Value, visited map[uintptr]*visit, depth int, co
 		visited[h] = &visit{addr, typ, seen}
 	}
 
-	if config.Transformers != nil && !isEmptyValue(dst) {
+	if config.Transformers != nil && !isReflectNil(dst) && dst.IsValid() {
 		if fn := config.Transformers.Transformer(dst.Type()); fn != nil {
 			err = fn(dst, src)
 			return

mergo.go

@@ -17,7 +17,7 @@ import (
 var (
 	ErrNilArguments                = errors.New("src and dst must not be nil")
 	ErrDifferentArgumentsTypes     = errors.New("src and dst must be of same type")
-	ErrNotSupported                = errors.New("only structs and maps are supported")
+	ErrNotSupported                = errors.New("only structs, maps, and slices are supported")
 	ErrExpectedMapAsDestination    = errors.New("dst was expected to be a map")
 	ErrExpectedStructAsDestination = errors.New("dst was expected to be a struct")
 	ErrNonPointerAgument           = errors.New("dst must be a pointer")
@@ -65,7 +65,7 @@ func resolveValues(dst, src interface{}) (vDst, vSrc reflect.Value, err error) {
 		return
 	}
 	vDst = reflect.ValueOf(dst).Elem()
-	if vDst.Kind() != reflect.Struct && vDst.Kind() != reflect.Map {
+	if vDst.Kind() != reflect.Struct && vDst.Kind() != reflect.Map && vDst.Kind() != reflect.Slice {
 		err = ErrNotSupported
 		return
 	}

mergo_test.go

@@ -13,7 +13,7 @@ import (
 	"time"
 
 	"github.com/imdario/mergo"
-	"gopkg.in/yaml.v2"
+	"gopkg.in/yaml.v3"
 )
 
 type simpleTest struct {
@@ -603,18 +603,18 @@ func TestMapsWithNilPointer(t *testing.T) {
 func TestYAMLMaps(t *testing.T) {
 	thing := loadYAML("testdata/thing.yml")
 	license := loadYAML("testdata/license.yml")
-	ft := thing["fields"].(map[interface{}]interface{})
-	fl := license["fields"].(map[interface{}]interface{})
+	ft := thing["fields"].(map[string]interface{})
+	fl := license["fields"].(map[string]interface{})
 	// license has one extra field (site) and another already existing in thing (author) that Mergo won't override.
 	expectedLength := len(ft) + len(fl) - 1
 	if err := mergo.Merge(&license, thing); err != nil {
 		t.Error(err.Error())
 	}
-	currentLength := len(license["fields"].(map[interface{}]interface{}))
+	currentLength := len(license["fields"].(map[string]interface{}))
 	if currentLength != expectedLength {
 		t.Errorf(`thing not merged in license properly, license must have %d elements instead of %d`, expectedLength, currentLength)
 	}
-	fields := license["fields"].(map[interface{}]interface{})
+	fields := license["fields"].(map[string]interface{})
 	if _, ok := fields["id"]; !ok {
 		t.Errorf(`thing not merged in license properly, license must have a new id field from thing`)
 	}
@@ -930,11 +930,11 @@ func TestMergeMapWithInnerSliceOfDifferentType(t *testing.T) {
 	}
 }
 
-func TestMergeSlicesIsNotSupported(t *testing.T) {
+func TestMergeDifferentSlicesIsNotSupported(t *testing.T) {
 	src := []string{"a", "b"}
 	dst := []int{1, 2}
 
-	if err := mergo.Merge(&src, &dst, mergo.WithOverride, mergo.WithAppendSlice); err != mergo.ErrNotSupported {
+	if err := mergo.Merge(&src, &dst, mergo.WithOverride, mergo.WithAppendSlice); err != mergo.ErrDifferentArgumentsTypes {
 		t.Errorf("expected %q, got %q", mergo.ErrNotSupported, err)
 	}
 }

pr211_2_test.go

@@ -0,0 +1,25 @@
+package mergo
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+type transformer struct {
+}
+
+func (s *transformer) Transformer(t reflect.Type) func(dst, src reflect.Value) error {
+	return nil
+}
+
+func Test_deepMergeTransformerInvalidDestination(t *testing.T) {
+	foo := time.Time{}
+	src := reflect.ValueOf(foo)
+	deepMerge(reflect.Value{}, src, make(map[uintptr]*visit), 0, &Config{
+		Transformers: &transformer{},
+	})
+	// this test is intentionally not asserting on anything, it's sole
+	// purpose to verify deepMerge doesn't panic when a transformer is
+	// passed and the destination is invalid.
+}

pr211_test.go

@@ -0,0 +1,36 @@
+package mergo_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/imdario/mergo"
+)
+
+func TestMergeWithTransformerZeroValue(t *testing.T) {
+	// This test specifically tests that a transformer can be used to
+	// prevent overwriting a zero value (in this case a bool). This would fail prior to #211
+	type fooWithBoolPtr struct {
+		b *bool
+	}
+	var Bool = func(b bool) *bool { return &b }
+	a := fooWithBoolPtr{b: Bool(false)}
+	b := fooWithBoolPtr{b: Bool(true)}
+
+	if err := mergo.Merge(&a, &b, mergo.WithTransformers(&transformer{
+		m: map[reflect.Type]func(dst, src reflect.Value) error{
+			reflect.TypeOf(Bool(false)): func(dst, src reflect.Value) error {
+				if dst.CanSet() && dst.IsNil() {
+					dst.Set(src)
+				}
+				return nil
+			},
+		},
+	})); err != nil {
+		t.Error(err)
+	}
+
+	if *a.b != false {
+		t.Errorf("b not merged in properly: a.b(%v) != expected(%v)", a.b, false)
+	}
+}