Upgrade imdario/mergo to v0.3.5

Mainly to get inline with `docker/cli` version of that dependency

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

integration-cli/docker_cli_events_unix_test.go

@@ -436,7 +436,7 @@ func (s *DockerDaemonSuite) TestDaemonEvents(c *check.C) {
 		"(allow-nondistributable-artifacts=[",
 		" cluster-advertise=, ",
 		" cluster-store=, ",
-		" cluster-store-opts={",
+		" cluster-store-opts=",
 		" debug=true, ",
 		" default-ipc-mode=",
 		" default-runtime=",

vendor.conf

@@ -23,7 +23,7 @@ github.com/gotestyourself/gotestyourself cf3a5ab914a2efa8bc838d09f5918c1d44d029
 github.com/google/go-cmp v0.2.0
 
 github.com/RackSec/srslog 456df3a81436d29ba874f3590eeeee25d666f8a5
-github.com/imdario/mergo 0.2.1
+github.com/imdario/mergo v0.3.5
 golang.org/x/sync fd80eb99c8f653c847d294a001bdf2a3a6f768f5
 
 # buildkit

vendor/github.com/imdario/mergo/README.md

@@ -2,31 +2,72 @@
 
 A helper to merge structs and maps in Golang. Useful for configuration default values, avoiding messy if-statements.
 
-Also a lovely [comune](http://en.wikipedia.org/wiki/Mergo) (municipality) in the Province of Ancona in the Italian region Marche.
-
-![Mergo dall'alto](http://www.comune.mergo.an.it/Siti/Mergo/Immagini/Foto/mergo_dall_alto.jpg)
+Also a lovely [comune](http://en.wikipedia.org/wiki/Mergo) (municipality) in the Province of Ancona in the Italian region of Marche.
 
 ## Status
 
-It is ready for production use. It works fine after extensive use in the wild.
+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).
 
+[![GoDoc][3]][4]
+[![GoCard][5]][6]
 [![Build Status][1]][2]
-[![GoDoc](https://godoc.org/github.com/imdario/mergo?status.svg)](https://godoc.org/github.com/imdario/mergo)
+[![Coverage Status][7]][8]
+[![Sourcegraph][9]][10]
 
 [1]: https://travis-ci.org/imdario/mergo.png
 [2]: https://travis-ci.org/imdario/mergo
+[3]: https://godoc.org/github.com/imdario/mergo?status.svg
+[4]: https://godoc.org/github.com/imdario/mergo
+[5]: https://goreportcard.com/badge/imdario/mergo
+[6]: https://goreportcard.com/report/github.com/imdario/mergo
+[7]: https://coveralls.io/repos/github/imdario/mergo/badge.svg?branch=master
+[8]: https://coveralls.io/github/imdario/mergo?branch=master
+[9]: https://sourcegraph.com/github.com/imdario/mergo/-/badge.svg
+[10]: https://sourcegraph.com/github.com/imdario/mergo?badge
+
+### Latest release
+
+[Release v0.3.4](https://github.com/imdario/mergo/releases/tag/v0.3.4).
 
 ### Important note
 
-Mergo is intended to assign **only** zero value fields on destination with source value. Since April 6th it works like this. Before it didn't work properly, causing some random overwrites. After some issues and PRs I found it didn't merge as I designed it. Thanks to [imdario/mergo#8](https://github.com/imdario/mergo/pull/8) overwriting functions were added and the wrong behavior was clearly detected.
+Please 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). An optional/variadic argument has been added, so it won't break existing code.
 
 If you were using Mergo **before** April 6th 2015, please check your project works as intended after updating your local copy with ```go get -u github.com/imdario/mergo```. I apologize for any issue caused by its previous behavior and any future bug that Mergo could cause (I hope it won't!) in existing projects after the change (release 0.2.0).
 
+### Donations
+
+If Mergo is useful to you, consider buying me a coffee, a beer or making a monthly donation so I can 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>
+
 ### Mergo in the wild
 
+- [moby/moby](https://github.com/moby/moby)
+- [kubernetes/kubernetes](https://github.com/kubernetes/kubernetes)
+- [vmware/dispatch](https://github.com/vmware/dispatch)
+- [Shopify/themekit](https://github.com/Shopify/themekit)
 - [imdario/zas](https://github.com/imdario/zas)
-- [GoogleCloudPlatform/kubernetes](https://github.com/GoogleCloudPlatform/kubernetes)
+- [matcornic/hermes](https://github.com/matcornic/hermes)
+- [OpenBazaar/openbazaar-go](https://github.com/OpenBazaar/openbazaar-go)
+- [kataras/iris](https://github.com/kataras/iris)
+- [michaelsauter/crane](https://github.com/michaelsauter/crane)
+- [go-task/task](https://github.com/go-task/task)
+- [sensu/uchiwa](https://github.com/sensu/uchiwa)
+- [ory/hydra](https://github.com/ory/hydra)
+- [sisatech/vcli](https://github.com/sisatech/vcli)
+- [dairycart/dairycart](https://github.com/dairycart/dairycart)
+- [projectcalico/felix](https://github.com/projectcalico/felix)
+- [resin-os/balena](https://github.com/resin-os/balena)
+- [go-kivik/kivik](https://github.com/go-kivik/kivik)
+- [Telefonica/govice](https://github.com/Telefonica/govice)
+- [supergiant/supergiant](supergiant/supergiant)
+- [SergeyTsalkov/brooce](https://github.com/SergeyTsalkov/brooce)
 - [soniah/dnsmadeeasy](https://github.com/soniah/dnsmadeeasy)
+- [ohsu-comp-bio/funnel](https://github.com/ohsu-comp-bio/funnel)
 - [EagerIO/Stout](https://github.com/EagerIO/Stout)
 - [lynndylanhurley/defsynth-api](https://github.com/lynndylanhurley/defsynth-api)
 - [russross/canvasassignments](https://github.com/russross/canvasassignments)
@@ -44,6 +85,7 @@ If you were using Mergo **before** April 6th 2015, please check your project wor
 - [thoas/picfit](https://github.com/thoas/picfit)
 - [mantasmatelis/whooplist-server](https://github.com/mantasmatelis/whooplist-server)
 - [jnuthong/item_search](https://github.com/jnuthong/item_search)
+- [bukalapak/snowboard](https://github.com/bukalapak/snowboard)
 
 ## Installation
 
@@ -56,19 +98,31 @@ If you were using Mergo **before** April 6th 2015, please check your project wor
 
 ## Usage
 
-You can only merge same-type structs with exported fields initialized as zero value of their type and same-types maps. Mergo won't merge unexported (private) fields but will do recursively any exported one. Also maps will be merged recursively except for structs inside maps (because they are not addressable using Go reflection).
+You can only merge same-type structs with exported fields initialized as zero value of their type and same-types maps. Mergo won't merge unexported (private) fields but will do recursively any exported one. It won't merge empty structs value as [they are not considered zero values](https://golang.org/ref/spec#The_zero_value) either. Also maps will be merged recursively except for structs inside maps (because they are not addressable using Go reflection).
 
-    if err := mergo.Merge(&dst, src); err != nil {
-        // ...
-    }
+```go
+if err := mergo.Merge(&dst, src); err != nil {
+    // ...
+}
+```
 
-Additionally, you can map a map[string]interface{} to a struct (and otherwise, from struct to map), following the same restrictions as in Merge(). Keys are capitalized to find each corresponding exported field.
+Also, you can merge overwriting values using the transformer `WithOverride`.
 
-    if err := mergo.Map(&dst, srcMap); err != nil {
-        // ...
-    }
+```go
+if err := mergo.Merge(&dst, src, mergo.WithOverride); err != nil {
+    // ...
+}
+```
 
-Warning: if you map a struct to map, it won't do it recursively. Don't expect Mergo to map struct members of your struct as map[string]interface{}. They will be just assigned as values.
+Additionally, you can map a `map[string]interface{}` to a struct (and otherwise, from struct to map), following the same restrictions as in `Merge()`. Keys are capitalized to find each corresponding exported field.
+
+```go
+if err := mergo.Map(&dst, srcMap); err != nil {
+    // ...
+}
+```
+
+Warning: if you map a struct to map, it won't do it recursively. Don't expect Mergo to map struct members of your struct as `map[string]interface{}`. They will be just assigned as values.
 
 More information and examples in [godoc documentation](http://godoc.org/github.com/imdario/mergo).
 
@@ -90,15 +144,12 @@ type Foo struct {
 func main() {
 	src := Foo{
 		A: "one",
+		B: 2,
 	}
-
 	dest := Foo{
 		A: "two",
-		B: 2,
 	}
-
 	mergo.Merge(&dest, src)
-
 	fmt.Println(dest)
 	// Will print
 	// {two 2}
@@ -107,7 +158,56 @@ func main() {
 
 Note: if test are failing due missing package, please execute:
 
-    go get gopkg.in/yaml.v1
+    go get gopkg.in/yaml.v2
+
+### Transformers
+
+Transformers allow to merge specific types differently than in the default behavior. In other words, now you can customize how some types are merged. For example, `time.Time` is a struct; it doesn't have zero value but IsZero can return true because it has fields with zero value. How can we merge a non-zero `time.Time`?
+
+```go
+package main
+
+import (
+	"fmt"
+	"github.com/imdario/mergo"
+        "reflect"
+        "time"
+)
+
+type timeTransfomer struct {
+}
+
+func (t timeTransfomer) Transformer(typ reflect.Type) func(dst, src reflect.Value) error {
+	if typ == reflect.TypeOf(time.Time{}) {
+		return func(dst, src reflect.Value) error {
+			if dst.CanSet() {
+				isZero := dst.MethodByName("IsZero")
+				result := isZero.Call([]reflect.Value{})
+				if result[0].Bool() {
+					dst.Set(src)
+				}
+			}
+			return nil
+		}
+	}
+	return nil
+}
+
+type Snapshot struct {
+	Time time.Time
+	// ...
+}
+
+func main() {
+	src := Snapshot{time.Now()}
+	dest := Snapshot{}
+	mergo.Merge(&dest, src, mergo.WithTransformers(timeTransfomer{}))
+	fmt.Println(dest)
+	// Will print
+	// { 2018-01-12 01:15:00 +0000 UTC m=+0.000000001 }
+}
+```
+
 
 ## Contact me
 

vendor/github.com/imdario/mergo/map.go

@@ -31,7 +31,8 @@ func isExported(field reflect.StructField) bool {
 // Traverses recursively both values, assigning src's fields values to dst.
 // The map argument tracks comparisons that have already been seen, which allows
 // short circuiting on recursive types.
-func deepMap(dst, src reflect.Value, visited map[uintptr]*visit, depth int, overwrite bool) (err error) {
+func deepMap(dst, src reflect.Value, visited map[uintptr]*visit, depth int, config *Config) (err error) {
+	overwrite := config.Overwrite
 	if dst.CanAddr() {
 		addr := dst.UnsafeAddr()
 		h := 17 * addr
@@ -61,6 +62,13 @@ func deepMap(dst, src reflect.Value, visited map[uintptr]*visit, depth int, over
 				dstMap[fieldName] = src.Field(i).Interface()
 			}
 		}
+	case reflect.Ptr:
+		if dst.IsNil() {
+			v := reflect.New(dst.Type().Elem())
+			dst.Set(v)
+		}
+		dst = dst.Elem()
+		fallthrough
 	case reflect.Struct:
 		srcMap := src.Interface().(map[string]interface{})
 		for key := range srcMap {
@@ -85,21 +93,24 @@ func deepMap(dst, src reflect.Value, visited map[uintptr]*visit, depth int, over
 					srcKind = reflect.Ptr
 				}
 			}
+
 			if !srcElement.IsValid() {
 				continue
 			}
 			if srcKind == dstKind {
-				if err = deepMerge(dstElement, srcElement, visited, depth+1, overwrite); err != nil {
+				if err = deepMerge(dstElement, srcElement, visited, depth+1, config); err != nil {
 					return
 				}
-			} else {
-				if srcKind == reflect.Map {
-					if err = deepMap(dstElement, srcElement, visited, depth+1, overwrite); err != nil {
-						return
-					}
-				} else {
-					return fmt.Errorf("type mismatch on %s field: found %v, expected %v", fieldName, srcKind, dstKind)
+			} else if dstKind == reflect.Interface && dstElement.Kind() == reflect.Interface {
+				if err = deepMerge(dstElement, srcElement, visited, depth+1, config); err != nil {
+					return
+				}
+			} else if srcKind == reflect.Map {
+				if err = deepMap(dstElement, srcElement, visited, depth+1, config); err != nil {
+					return
 				}
+			} else {
+				return fmt.Errorf("type mismatch on %s field: found %v, expected %v", fieldName, srcKind, dstKind)
 			}
 		}
 	}
@@ -117,26 +128,35 @@ func deepMap(dst, src reflect.Value, visited map[uintptr]*visit, depth int, over
 // doesn't apply if dst is a map.
 // This is separated method from Merge because it is cleaner and it keeps sane
 // semantics: merging equal types, mapping different (restricted) types.
-func Map(dst, src interface{}) error {
-	return _map(dst, src, false)
+func Map(dst, src interface{}, opts ...func(*Config)) error {
+	return _map(dst, src, opts...)
 }
 
-func MapWithOverwrite(dst, src interface{}) error {
-	return _map(dst, src, true)
+// MapWithOverwrite will do the same as Map except that non-empty dst attributes will be overridden by
+// non-empty src attribute values.
+// Deprecated: Use Map(…) with WithOverride
+func MapWithOverwrite(dst, src interface{}, opts ...func(*Config)) error {
+	return _map(dst, src, append(opts, WithOverride)...)
 }
 
-func _map(dst, src interface{}, overwrite bool) error {
+func _map(dst, src interface{}, opts ...func(*Config)) error {
 	var (
 		vDst, vSrc reflect.Value
 		err        error
 	)
+	config := &Config{}
+
+	for _, opt := range opts {
+		opt(config)
+	}
+
 	if vDst, vSrc, err = resolveValues(dst, src); err != nil {
 		return err
 	}
 	// To be friction-less, we redirect equal-type arguments
 	// to deepMerge. Only because arguments can be anything.
 	if vSrc.Kind() == vDst.Kind() {
-		return deepMerge(vDst, vSrc, make(map[uintptr]*visit), 0, overwrite)
+		return deepMerge(vDst, vSrc, make(map[uintptr]*visit), 0, config)
 	}
 	switch vSrc.Kind() {
 	case reflect.Struct:
@@ -150,5 +170,5 @@ func _map(dst, src interface{}, overwrite bool) error {
 	default:
 		return ErrNotSupported
 	}
-	return deepMap(vDst, vSrc, make(map[uintptr]*visit), 0, overwrite)
+	return deepMap(vDst, vSrc, make(map[uintptr]*visit), 0, config)
 }

vendor/github.com/imdario/mergo/merge.go

@@ -12,10 +12,34 @@ import (
 	"reflect"
 )
 
+func hasExportedField(dst reflect.Value) (exported bool) {
+	for i, n := 0, dst.NumField(); i < n; i++ {
+		field := dst.Type().Field(i)
+		if field.Anonymous && dst.Field(i).Kind() == reflect.Struct {
+			exported = exported || hasExportedField(dst.Field(i))
+		} else {
+			exported = exported || len(field.PkgPath) == 0
+		}
+	}
+	return
+}
+
+type Config struct {
+	Overwrite    bool
+	AppendSlice  bool
+	Transformers Transformers
+}
+
+type Transformers interface {
+	Transformer(reflect.Type) func(dst, src reflect.Value) error
+}
+
 // Traverses recursively both values, assigning src's fields values to dst.
 // The map argument tracks comparisons that have already been seen, which allows
 // short circuiting on recursive types.
-func deepMerge(dst, src reflect.Value, visited map[uintptr]*visit, depth int, overwrite bool) (err error) {
+func deepMerge(dst, src reflect.Value, visited map[uintptr]*visit, depth int, config *Config) (err error) {
+	overwrite := config.Overwrite
+
 	if !src.IsValid() {
 		return
 	}
@@ -32,14 +56,31 @@ func deepMerge(dst, src reflect.Value, visited map[uintptr]*visit, depth int, ov
 		// Remember, remember...
 		visited[h] = &visit{addr, typ, seen}
 	}
+
+	if config.Transformers != nil && !isEmptyValue(dst) {
+		if fn := config.Transformers.Transformer(dst.Type()); fn != nil {
+			err = fn(dst, src)
+			return
+		}
+	}
+
 	switch dst.Kind() {
 	case reflect.Struct:
-		for i, n := 0, dst.NumField(); i < n; i++ {
-			if err = deepMerge(dst.Field(i), src.Field(i), visited, depth+1, overwrite); err != nil {
-				return
+		if hasExportedField(dst) {
+			for i, n := 0, dst.NumField(); i < n; i++ {
+				if err = deepMerge(dst.Field(i), src.Field(i), visited, depth+1, config); err != nil {
+					return
+				}
+			}
+		} else {
+			if dst.CanSet() && !isEmptyValue(src) && (overwrite || isEmptyValue(dst)) {
+				dst.Set(src)
 			}
 		}
 	case reflect.Map:
+		if dst.IsNil() && !src.IsNil() {
+			dst.Set(reflect.MakeMap(dst.Type()))
+		}
 		for _, key := range src.MapKeys() {
 			srcElement := src.MapIndex(key)
 			if !srcElement.IsValid() {
@@ -47,40 +88,99 @@ func deepMerge(dst, src reflect.Value, visited map[uintptr]*visit, depth int, ov
 			}
 			dstElement := dst.MapIndex(key)
 			switch srcElement.Kind() {
-			case reflect.Chan, reflect.Func, reflect.Map, reflect.Ptr, reflect.Interface, reflect.Slice:
+			case reflect.Chan, reflect.Func, reflect.Map, reflect.Interface, reflect.Slice:
 				if srcElement.IsNil() {
 					continue
 				}
 				fallthrough
 			default:
+				if !srcElement.CanInterface() {
+					continue
+				}
 				switch reflect.TypeOf(srcElement.Interface()).Kind() {
 				case reflect.Struct:
 					fallthrough
 				case reflect.Ptr:
 					fallthrough
 				case reflect.Map:
-					if err = deepMerge(dstElement, srcElement, visited, depth+1, overwrite); err != nil {
+					srcMapElm := srcElement
+					dstMapElm := dstElement
+					if srcMapElm.CanInterface() {
+						srcMapElm = reflect.ValueOf(srcMapElm.Interface())
+						if dstMapElm.IsValid() {
+							dstMapElm = reflect.ValueOf(dstMapElm.Interface())
+						}
+					}
+					if err = deepMerge(dstMapElm, srcMapElm, visited, depth+1, config); err != nil {
 						return
 					}
+				case reflect.Slice:
+					srcSlice := reflect.ValueOf(srcElement.Interface())
+
+					var dstSlice reflect.Value
+					if !dstElement.IsValid() || dstElement.IsNil() {
+						dstSlice = reflect.MakeSlice(srcSlice.Type(), 0, srcSlice.Len())
+					} else {
+						dstSlice = reflect.ValueOf(dstElement.Interface())
+					}
+
+					if !isEmptyValue(src) && (overwrite || isEmptyValue(dst)) && !config.AppendSlice {
+						dstSlice = srcSlice
+					} else if config.AppendSlice {
+						dstSlice = reflect.AppendSlice(dstSlice, srcSlice)
+					}
+					dst.SetMapIndex(key, dstSlice)
 				}
 			}
-			if !isEmptyValue(srcElement) && (overwrite || (!dstElement.IsValid() || isEmptyValue(dst))) {
+			if dstElement.IsValid() && reflect.TypeOf(srcElement.Interface()).Kind() == reflect.Map {
+				continue
+			}
+
+			if srcElement.IsValid() && (overwrite || (!dstElement.IsValid() || isEmptyValue(dstElement))) {
 				if dst.IsNil() {
 					dst.Set(reflect.MakeMap(dst.Type()))
 				}
 				dst.SetMapIndex(key, srcElement)
 			}
 		}
+	case reflect.Slice:
+		if !dst.CanSet() {
+			break
+		}
+		if !isEmptyValue(src) && (overwrite || isEmptyValue(dst)) && !config.AppendSlice {
+			dst.Set(src)
+		} else if config.AppendSlice {
+			dst.Set(reflect.AppendSlice(dst, src))
+		}
 	case reflect.Ptr:
 		fallthrough
 	case reflect.Interface:
 		if src.IsNil() {
 			break
-		} else if dst.IsNil() {
+		}
+		if src.Kind() != reflect.Interface {
+			if dst.IsNil() || overwrite {
+				if dst.CanSet() && (overwrite || isEmptyValue(dst)) {
+					dst.Set(src)
+				}
+			} else if src.Kind() == reflect.Ptr {
+				if err = deepMerge(dst.Elem(), src.Elem(), visited, depth+1, config); err != nil {
+					return
+				}
+			} else if dst.Elem().Type() == src.Type() {
+				if err = deepMerge(dst.Elem(), src, visited, depth+1, config); err != nil {
+					return
+				}
+			} else {
+				return ErrDifferentArgumentsTypes
+			}
+			break
+		}
+		if dst.IsNil() || overwrite {
 			if dst.CanSet() && (overwrite || isEmptyValue(dst)) {
 				dst.Set(src)
 			}
-		} else if err = deepMerge(dst.Elem(), src.Elem(), visited, depth+1, overwrite); err != nil {
+		} else if err = deepMerge(dst.Elem(), src.Elem(), visited, depth+1, config); err != nil {
 			return
 		}
 	default:
@@ -91,30 +191,55 @@ func deepMerge(dst, src reflect.Value, visited map[uintptr]*visit, depth int, ov
 	return
 }
 
-// Merge sets fields' values in dst from src if they have a zero
-// value of their type.
-// dst and src must be valid same-type structs and dst must be
-// a pointer to struct.
-// It won't merge unexported (private) fields and will do recursively
-// any exported field.
-func Merge(dst, src interface{}) error {
-	return merge(dst, src, false)
+// Merge will fill any empty for value type attributes on the dst struct using corresponding
+// src attributes if they themselves are not empty. dst and src must be valid same-type structs
+// and dst must be a pointer to struct.
+// It won't merge unexported (private) fields and will do recursively any exported field.
+func Merge(dst, src interface{}, opts ...func(*Config)) error {
+	return merge(dst, src, opts...)
+}
+
+// MergeWithOverwrite will do the same as Merge except that non-empty dst attributes will be overriden by
+// non-empty src attribute values.
+// Deprecated: use Merge(…) with WithOverride
+func MergeWithOverwrite(dst, src interface{}, opts ...func(*Config)) error {
+	return merge(dst, src, append(opts, WithOverride)...)
+}
+
+// WithTransformers adds transformers to merge, allowing to customize the merging of some types.
+func WithTransformers(transformers Transformers) func(*Config) {
+	return func(config *Config) {
+		config.Transformers = transformers
+	}
+}
+
+// WithOverride will make merge override non-empty dst attributes with non-empty src attributes values.
+func WithOverride(config *Config) {
+	config.Overwrite = true
 }
 
-func MergeWithOverwrite(dst, src interface{}) error {
-	return merge(dst, src, true)
+// WithAppendSlice will make merge append slices instead of overwriting it
+func WithAppendSlice(config *Config) {
+	config.AppendSlice = true
 }
 
-func merge(dst, src interface{}, overwrite bool) error {
+func merge(dst, src interface{}, opts ...func(*Config)) error {
 	var (
 		vDst, vSrc reflect.Value
 		err        error
 	)
+
+	config := &Config{}
+
+	for _, opt := range opts {
+		opt(config)
+	}
+
 	if vDst, vSrc, err = resolveValues(dst, src); err != nil {
 		return err
 	}
 	if vDst.Type() != vSrc.Type() {
 		return ErrDifferentArgumentsTypes
 	}
-	return deepMerge(vDst, vSrc, make(map[uintptr]*visit), 0, overwrite)
+	return deepMerge(vDst, vSrc, make(map[uintptr]*visit), 0, config)
 }

vendor/github.com/imdario/mergo/mergo.go

@@ -32,7 +32,7 @@ type visit struct {
 	next *visit
 }
 
-// From src/pkg/encoding/json.
+// From src/pkg/encoding/json/encode.go.
 func isEmptyValue(v reflect.Value) bool {
 	switch v.Kind() {
 	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
@@ -46,7 +46,14 @@ func isEmptyValue(v reflect.Value) bool {
 	case reflect.Float32, reflect.Float64:
 		return v.Float() == 0
 	case reflect.Interface, reflect.Ptr:
+		if v.IsNil() {
+			return true
+		}
+		return isEmptyValue(v.Elem())
+	case reflect.Func:
 		return v.IsNil()
+	case reflect.Invalid:
+		return true
 	}
 	return false
 }