Fix: use exceptional copy method for Go standard types

.github/workflows/go.yml

@@ -13,19 +13,19 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: ["1.18.x", "1.22.x", "1.23.x"]
+        go: ["1.18.x", "1.23.x", "1.25.x"]
         include:
-          - go: 1.23.x
+          - go: 1.18.x
             latest: true
 
     steps:
       - name: Setup Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version: ${{ matrix.go }}
 
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
 
       - name: Load cached dependencies
         uses: actions/cache@v4
@@ -35,11 +35,11 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-go-
 
-      - name: Download Dependencies
-        run: make prepare
-
       - name: Lint
-        run: make lint
+        uses: golangci/golangci-lint-action@v8
+        with:
+          version: v2.4.0
+          args: --timeout=3m -v
 
       - name: Test
         run: make cover

.golangci.yaml

@@ -0,0 +1,87 @@
+version: "2"
+linters:
+  enable:
+    - bodyclose
+    - contextcheck
+    - copyloopvar
+    - dogsled
+    - err113
+    - errname
+    - errorlint
+    - exhaustive
+    - forbidigo
+    - forcetypeassert
+    - funlen
+    - gocognit
+    - goconst
+    - gocritic
+    - gocyclo
+    - gosec
+    - lll
+    - misspell
+    - mnd
+    - nakedret
+    - nestif
+    - nilerr
+    - rowserrcheck
+    - staticcheck
+    - unconvert
+    - unparam
+    - whitespace
+  settings:
+    funlen:
+      lines: 120
+      statements: 80
+    gocognit:
+      min-complexity: 30
+    gocyclo:
+      min-complexity: 30
+    lll:
+      line-length: 120
+    misspell:
+      locale: US
+  exclusions:
+    generated: lax
+    presets:
+      - comments
+      - common-false-positives
+      - legacy
+      - std-error-handling
+    rules:
+      - linters:
+          - contextcheck
+          - err113
+          - forcetypeassert
+          - funlen
+          - gocognit
+          - gocyclo
+          - gosec
+          - mnd
+          - staticcheck
+          - unused
+          - wrapcheck
+        path: _test\.go
+    paths:
+      - third_party$
+      - builtin$
+      - examples$
+formatters:
+  enable:
+    - gci
+    - gofmt
+    - goimports
+  settings:
+    gci:
+      sections:
+        - standard
+        - default
+        - prefix(github.com/tiendc/go-deepcopy)
+    goimports:
+      local-prefixes:
+        - github.com/golangci/golangci-lint
+  exclusions:
+    generated: lax
+    paths:
+      - third_party$
+      - builtin$
+      - examples$

Makefile

@@ -1,7 +1,7 @@
 all: lint test
 
 prepare:
-	@curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(shell go env GOPATH)/bin v1.60.3
+	@curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/HEAD/install.sh | sh -s -- -b $(go env GOPATH)/bin v2.4.0
 
 build:
 	@go build -v ./...

build_copier.go

@@ -3,6 +3,7 @@ package deepcopy
 import (
 	"fmt"
 	"reflect"
+	"strings"
 	"sync"
 )
 
@@ -171,8 +172,14 @@ func buildCopier(ctx *Context, dstType, srcType reflect.Type) (copier copier, er
 	//nolint:nestif
 	if srcKind == reflect.Struct {
 		if dstKind == reflect.Struct {
-			// At this point, cachedCopier should be `nil`.
-			// If it's non-nil, seems like a circular reference occurs, use an inline copier.
+			// Build a special copier for Go standard types such as time.Time, unique.Handle
+			copier = buildCopierForStandardStructs(dstType, srcType)
+			if copier != nil {
+				goto OnComplete
+			}
+
+			// At this point, cached copier should not exist in the cache map.
+			// If it exists, seems like a circular reference occurs, use an inline copier.
 			if cachedCopierFound {
 				return &inlineCopier{ctx: ctx, dstType: dstType, srcType: srcType}, nil
 			}
@@ -226,6 +233,30 @@ OnNonCopyable:
 	return nil, fmt.Errorf("%w: %v -> %v", ErrTypeNonCopyable, srcType, dstType)
 }
 
+func buildCopierForStandardStructs(dstType, srcType reflect.Type) copier {
+	switch srcType.PkgPath() {
+	// When copy time.Time -> time.Time or derived type
+	case "time":
+		if dstType == srcType {
+			return defaultDirectCopier
+		}
+		if dstType.ConvertibleTo(srcType) {
+			return defaultConvCopier
+		}
+	// When copy unique.Handle[T] -> unique.Handle[T] or derived type
+	case "unique":
+		if strings.HasPrefix(srcType.Name(), "Handle[") {
+			if dstType == srcType {
+				return defaultDirectCopier
+			}
+			if dstType.ConvertibleTo(srcType) {
+				return defaultConvCopier
+			}
+		}
+	}
+	return nil
+}
+
 func setCachedCopier(ctx *Context, cacheKey *cacheKey, cp copier) {
 	ctx.mu.Lock()
 	ctx.copierCacheMap[*cacheKey] = cp

go.mod

@@ -2,7 +2,7 @@ module github.com/tiendc/go-deepcopy
 
 go 1.18
 
-require github.com/stretchr/testify v1.9.0
+require github.com/stretchr/testify v1.11.1
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect

go.sum

@@ -2,8 +2,8 @@ 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 v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
-github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 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.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

struct_copier_go1.23_test.go

@@ -0,0 +1,62 @@
+//go:build go1.23
+
+package deepcopy
+
+import (
+	"testing"
+	"unique"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_Copy_struct_on_standard_types_go1_23(t *testing.T) {
+	t.Run("#1: Copy unique.Handle[string]", func(t *testing.T) {
+		s := unique.Make("hello")
+		var d unique.Handle[string]
+		err := Copy(&d, s)
+		assert.Nil(t, err)
+		assert.Equal(t, d, s)
+		assert.Equal(t, d.Value(), s.Value())
+
+		// unique.Handle[T] as struct fields
+		type A struct {
+			I int
+		}
+		type S struct {
+			H unique.Handle[A]
+		}
+		type D struct {
+			H unique.Handle[A]
+		}
+		s2 := S{H: unique.Make(A{I: 111})}
+		var d2 D
+		err = Copy(&d2, s2)
+		assert.Nil(t, err)
+		assert.Equal(t, d2.H, s2.H)
+		assert.Equal(t, d2.H.Value(), s2.H.Value())
+	})
+
+	t.Run("#2: Copy unique.Handle[string] to derived type", func(t *testing.T) {
+		type T unique.Handle[string]
+		s := unique.Make("hello")
+		var d T
+		err := Copy(&d, s)
+		assert.Nil(t, err)
+		assert.Equal(t, unique.Handle[string](d), s)
+		assert.Equal(t, unique.Handle[string](d).Value(), s.Value())
+
+		// unique.Handle[T] as struct fields
+		type S struct {
+			H unique.Handle[string]
+		}
+		type D struct {
+			H T
+		}
+		s2 := S{H: unique.Make("hello")}
+		var d2 D
+		err = Copy(&d2, s2)
+		assert.Nil(t, err)
+		assert.Equal(t, unique.Handle[string](d2.H), s2.H)
+		assert.Equal(t, unique.Handle[string](d2.H).Value(), s2.H.Value())
+	})
+}