init

.github/workflows/list.yml

@@ -0,0 +1,23 @@
+name: list
+
+on:
+  push:
+    tags:
+      - "v*.*.*"
+  workflow_dispatch:
+jobs:
+  list:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: actions/setup-go@v4
+        with:
+          go-version-file: 'go.mod'
+
+      - run: go mod download
+      - run: go test ./...
+
+      - env:
+          GOPROXY: "proxy.golang.org"
+        run: go list -m github.com/cardinalby/go-dto-merge@${{ github.ref_name }}

.github/workflows/test.yml

@@ -0,0 +1,20 @@
+name: test
+
+on:
+  push:
+    branches:
+      - "**"
+  workflow_dispatch:
+  pull_request:
+jobs:
+  test:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: actions/setup-go@v4
+        with:
+          go-version-file: 'go.mod'
+
+      - run: go mod download
+      - run: go test ./...

.gitignore

@@ -0,0 +1,2 @@
+.idea
+vendor

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024 Cardinal
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -0,0 +1,128 @@
+[![test](https://github.com/cardinalby/go-dto-merge/actions/workflows/test.yml/badge.svg)](https://github.com/cardinalby/go-dto-merge/actions/workflows/test.yml)
+[![list](https://github.com/cardinalby/go-dto-merge/actions/workflows/list.yml/badge.svg)](https://github.com/cardinalby/go-dto-merge/actions/workflows/list.yml)
+[![Go Reference](https://pkg.go.dev/badge/github.com/cardinalby/go-dto-merge.svg)](https://pkg.go.dev/github.com/cardinalby/go-dto-merge)
+
+# dtomerge package
+
+This package provides a way to deep merge two structs of the same type.
+
+It's useful for merging **default** values with **user-provided** values (e.g. configs).
+Values that are not present in the user-provided struct will be taken from the default struct.
+
+**Only exported** fields are merged.
+
+## Example
+```
+go get github.com/cardinalby/go-dto-merge
+```
+
+Example `Config` struct has a nested `UserConfig` struct. 
+```go
+
+import "github.com/cardinalby/go-dto-merge"
+
+type UserConfig struct {
+    Role string      // for non-pointer fields zero value indicates it's not specified
+    Name string
+}
+
+type Config struct {
+    Verbose *bool    // it is a pointer to distinguish between "not specified" and false
+    User UserConfig
+}
+```
+
+Given defaults, we can merge them with user-provided values:
+```go
+// ptr is some helper function to create a pointer to a value
+defaults := Config{     // it's called "src"
+    Verbose: ptr(true),
+    User: UserConfig{
+        Role: "admin",
+        Name: "John",
+    },
+}
+userProvided := Config{  // it's called "patch"
+    User: UserConfig{
+        Name: "Jane",
+    },
+}
+res, err := dtomerge.Merge(defaults, userProvided) // (src, patch)
+
+// res == Config{
+//     Verbose: (*bool) true,
+//     User: UserConfig{
+//         Role: "admin",
+//         Name: "Jane",
+//     },
+// }
+```
+
+## Pointers
+Pointers can be used to distinguish between "not specified" and "explicit zero value" fields.
+- If `patch` field contains a nil pointer, it will not override `defaults.Verbose`
+- If `patch` field contains a pointer to zero value, it will override `src` field
+  only in case `src` pointer field is nil (value will be copied)
+- If `patch` field contains a pointer tp **non**-zero value, it will override `src` field (value will be copied)
+
+Use `dtomerge.OptDeRefPointers(false)` option to handle pointers as regular fields.
+
+## Slices and maps
+Setting additional option you can merge slices and maps as well.
+
+```go
+
+import (
+    "github.com/cardinalby/go-dto-merge"
+    "github.com/cardinalby/go-dto-merge/opt"
+)
+
+type Config struct {    
+    Roles []string
+    Permissions map[string]bool
+}
+
+defaults := Config{
+    Roles: []string{"admin", "user"},
+    Permissions: map[string]bool{
+        "read": true,
+        "write": false,
+    },
+}
+
+userProvided := Config{
+    Roles: []string{"user", "guest"},
+    Permissions: map[string]bool{
+        "write": true,
+    },
+}
+
+res, err := dtomerge.Merge(defaults, userProvided,
+    // merge map keys
+    dtomerge.OptIterateMaps(true),
+    // merge slices as unique sets
+    dtomerge.OptMergeSlices(dtomerge.SlicesMergeStrategyUnique), 		
+)
+
+// res == Config{
+//     Roles: []string{"admin", "user", "guest"},
+//     Permissions: map[string]bool{
+//         "read": true,
+//         "write": true,
+//     },
+// }
+```
+
+Possible `MergeSlices` strategies:
+- `dtomerge.SlicesMergeStrategyUnique`: `[1, 2, 3] + [4, 2, 1] → [1, 2, 3, 4]`
+- `dtomerge.SlicesMergeStrategyByIndex`: `[1, 2, 3] + [11, 12] → [11, 12, 3]`
+- `dtomerge.SlicesMergeStrategyAtomic`: merge as a whole, default
+
+## Other options
+You can: 
+- specify a custom merge function for a specific type.
+- specify a custom merge options for a specific type.
+
+See [options godoc](https://pkg.go.dev/github.com/cardinalby/go-dto-merge#Options) for more details.
+
+

any.go

@@ -0,0 +1,65 @@
+package dtomerge
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/cardinalby/go-dto-merge/types"
+)
+
+func mergeAny(src reflect.Value, patch reflect.Value, opts Options) (reflect.Value, error) {
+	srcType := src.Type()
+	patchType := patch.Type()
+	if srcType != patchType {
+		return reflect.Value{},
+			fmt.Errorf("%w: src type '%s' != patch type '%s'",
+				types.ErrInvalidTypes, srcType.Name(), patchType.Name())
+	}
+
+	customMergeFuncs, err := opts.getCustomReflectMergeFuncs()
+	if err != nil {
+		return reflect.Value{}, err
+	}
+
+	if mergeFn, has := customMergeFuncs[srcType]; has {
+		return mergeFn(src, patch)
+	}
+	if opts.RespectMergers {
+		mergeFn, isMerger := AsMerger(src)
+		if isMerger {
+			return mergeFn(patch)
+		}
+	}
+	if customOptions, ok := opts.CustomMergeOptions[srcType]; ok {
+		opts = customOptions
+	} else if opts.RespectMergeOptionsProviders {
+		if optionsProvider, ok := src.Interface().(MergeOptionsProvider); ok {
+			opts = optionsProvider.GetMergeOptions()
+		}
+	}
+
+	if opts.DeRefPointers && srcType.Kind() == reflect.Ptr {
+		return mergePointers(src, patch, opts)
+	}
+
+	if srcType.Kind() == reflect.Struct {
+		if _, isAtomic := opts.getAtomicTypesMap()[srcType]; !isAtomic {
+			return mergeStructs(src, patch, opts)
+		}
+	}
+
+	if opts.IterateMaps && srcType.Kind() == reflect.Map {
+		return mergeMaps(src, patch, opts)
+	}
+
+	if srcType.Kind() == reflect.Slice {
+		if srcType.Elem().Comparable() && opts.SlicesMerge == SlicesMergeStrategyUnique {
+			return mergeComparableSlicesUnique(src, patch, opts)
+		}
+		if opts.SlicesMerge == SlicesMergeStrategyByIndex {
+			return mergeSlicesByIndex(src, patch, opts)
+		}
+	}
+
+	return mergeSimpleValue(src, patch, opts)
+}

examples/1_simple_test.go

@@ -0,0 +1,45 @@
+package examples
+
+import (
+	"testing"
+
+	dtomerge "github.com/cardinalby/go-dto-merge"
+	"github.com/stretchr/testify/require"
+)
+
+func ptr[T any](v T) *T {
+	return &v
+}
+
+func TestSimpleExample(t *testing.T) {
+	t.Parallel()
+
+	type UserConfig struct {
+		Role string // for non-pointer fields zero value indicates it's not specified
+		Name string
+	}
+
+	type Config struct {
+		Verbose *bool // it is a pointer to distinguish between "not specified" and false
+		User    UserConfig
+	}
+
+	defaults := Config{
+		Verbose: ptr(true),
+		User: UserConfig{
+			Role: "admin",
+			Name: "John",
+		},
+	}
+	userProvided := Config{
+		User: UserConfig{
+			Name: "Jane",
+		},
+	}
+	res, err := dtomerge.Merge(defaults, userProvided)
+	require.NoError(t, err)
+
+	require.Equal(t, true, *res.Verbose)
+	require.Equal(t, "admin", res.User.Role)
+	require.Equal(t, "Jane", res.User.Name)
+}

examples/2_maps_slices_test.go

@@ -0,0 +1,44 @@
+package examples
+
+import (
+	"testing"
+
+	dtomerge "github.com/cardinalby/go-dto-merge"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSlicesMapsExample(t *testing.T) {
+	t.Parallel()
+
+	type Config struct {
+		Roles       []string
+		Permissions map[string]bool
+	}
+
+	defaults := Config{
+		Roles: []string{"admin", "user"},
+		Permissions: map[string]bool{
+			"read":  true,
+			"write": false,
+		},
+	}
+
+	userProvided := Config{
+		Roles: []string{"user", "guest"},
+		Permissions: map[string]bool{
+			"write": true,
+		},
+	}
+
+	res, err := dtomerge.Merge(defaults, userProvided,
+		dtomerge.OptIterateMaps(true),
+		dtomerge.OptMergeSlices(dtomerge.SlicesMergeStrategyUnique),
+	)
+	require.NoError(t, err)
+
+	require.Equal(t, []string{"admin", "user", "guest"}, res.Roles)
+	require.Equal(t, map[string]bool{
+		"read":  true,
+		"write": true,
+	}, res.Permissions)
+}

go.mod

@@ -0,0 +1,10 @@
+module github.com/cardinalby/go-dto-merge
+
+go 1.19
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/testify v1.8.4 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -0,0 +1,9 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=