[v4] fix flatten map util function (#211)

* add the fixed version of FlattenMap() and corresponding tests
* replaced the old FlattenMap() implementation with a new one

go.mod

@@ -12,6 +12,7 @@ require (
 	github.com/patrickmn/go-cache v2.1.0+incompatible
 	github.com/silas/dag v0.0.0-20220518035006-a7e85ada93c5
 	github.com/spf13/cast v1.7.1
+	github.com/stretchr/testify v1.10.0
 	go.uber.org/atomic v1.11.0
 	go.uber.org/automaxprocs v1.6.0
 	go.unistack.org/micro-proto/v4 v4.1.0
@@ -26,7 +27,6 @@ require (
 	github.com/pbnjay/memory v0.0.0-20210728143218-7b4eea64cf58 // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/rogpeppe/go-internal v1.13.1 // indirect
-	github.com/stretchr/testify v1.10.0 // indirect
 	golang.org/x/net v0.34.0 // indirect
 	golang.org/x/sys v0.29.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20241216192217-9240e9c98484 // indirect

util/reflect/struct.go

@@ -489,35 +489,74 @@ func URLMap(query string) (map[string]interface{}, error) {
 	return mp.(map[string]interface{}), nil
 }
 
-// FlattenMap expand key.subkey to nested map
-func FlattenMap(a map[string]interface{}) map[string]interface{} {
-	// preprocess map
-	nb := make(map[string]interface{}, len(a))
-	for k, v := range a {
-		ps := strings.Split(k, ".")
-		if len(ps) == 1 {
-			nb[k] = v
+// FlattenMap flattens a nested map into a single-level map using dot notation for nested keys.
+// In case of key conflicts, all nested levels will be discarded in favor of the first-level key.
+//
+// Example #1:
+//
+//	Input:
+//	  {
+//	    "user.name": "alex",
+//	    "user.document.id": "document_id"
+//	    "user.document.number": "document_number"
+//	  }
+//	Output:
+//	  {
+//	    "user": {
+//	      "name": "alex",
+//	      "document": {
+//	        "id": "document_id"
+//	        "number": "document_number"
+//	      }
+//	    }
+//	  }
+//
+// Example #2 (with conflicts):
+//
+//	Input:
+//	  {
+//	    "user": "alex",
+//	    "user.document.id": "document_id"
+//	    "user.document.number": "document_number"
+//	  }
+//	Output:
+//	  {
+//	    "user": "alex"
+//	  }
+func FlattenMap(input map[string]interface{}) map[string]interface{} {
+	result := make(map[string]interface{})
+
+	for k, v := range input {
+		parts := strings.Split(k, ".")
+
+		if len(parts) == 1 {
+			result[k] = v
 			continue
 		}
-		em := make(map[string]interface{})
-		em[ps[len(ps)-1]] = v
-		for i := len(ps) - 2; i > 0; i-- {
-			nm := make(map[string]interface{})
-			nm[ps[i]] = em
-			em = nm
-		}
-		if vm, ok := nb[ps[0]]; ok {
-			// nested map
-			nm := vm.(map[string]interface{})
-			for vk, vv := range em {
-				nm[vk] = vv
+
+		current := result
+
+		for i, part := range parts {
+			// last element in the path
+			if i == len(parts)-1 {
+				current[part] = v
+				break
+			}
+
+			// initialize map for current level if not exist
+			if _, ok := current[part]; !ok {
+				current[part] = make(map[string]interface{})
+			}
+
+			if nested, ok := current[part].(map[string]interface{}); ok {
+				current = nested // continue to the nested map
+			} else {
+				break // if current element is not a map, ignore it
 			}
-			nb[ps[0]] = nm
-		} else {
-			nb[ps[0]] = em
 		}
 	}
-	return nb
+
+	return result
 }
 
 /*

util/reflect/struct_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/require"
 	rutil "go.unistack.org/micro/v4/util/reflect"
 )
 
@@ -319,3 +320,140 @@ func TestIsZero(t *testing.T) {
 
 	// t.Logf("XX %#+v\n", ok)
 }
+
+func TestFlattenMap(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    map[string]interface{}
+		expected map[string]interface{}
+	}{
+		{
+			name:     "empty map",
+			input:    map[string]interface{}{},
+			expected: map[string]interface{}{},
+		},
+		{
+			name:     "nil map",
+			input:    nil,
+			expected: map[string]interface{}{},
+		},
+		{
+			name: "single level",
+			input: map[string]interface{}{
+				"username": "username",
+				"password": "password",
+			},
+			expected: map[string]interface{}{
+				"username": "username",
+				"password": "password",
+			},
+		},
+		{
+			name: "two level",
+			input: map[string]interface{}{
+				"order_id":      "order_id",
+				"user.name":     "username",
+				"user.password": "password",
+			},
+			expected: map[string]interface{}{
+				"order_id": "order_id",
+				"user": map[string]interface{}{
+					"name":     "username",
+					"password": "password",
+				},
+			},
+		},
+		{
+			name: "three level",
+			input: map[string]interface{}{
+				"order_id":             "order_id",
+				"user.name":            "username",
+				"user.password":        "password",
+				"user.document.id":     "document_id",
+				"user.document.number": "document_number",
+			},
+			expected: map[string]interface{}{
+				"order_id": "order_id",
+				"user": map[string]interface{}{
+					"name":     "username",
+					"password": "password",
+					"document": map[string]interface{}{
+						"id":     "document_id",
+						"number": "document_number",
+					},
+				},
+			},
+		},
+		{
+			name: "four level",
+			input: map[string]interface{}{
+				"order_id":                    "order_id",
+				"user.name":                   "username",
+				"user.password":               "password",
+				"user.document.id":            "document_id",
+				"user.document.number":        "document_number",
+				"user.info.permissions.read":  "available",
+				"user.info.permissions.write": "available",
+			},
+			expected: map[string]interface{}{
+				"order_id": "order_id",
+				"user": map[string]interface{}{
+					"name":     "username",
+					"password": "password",
+					"document": map[string]interface{}{
+						"id":     "document_id",
+						"number": "document_number",
+					},
+					"info": map[string]interface{}{
+						"permissions": map[string]interface{}{
+							"read":  "available",
+							"write": "available",
+						},
+					},
+				},
+			},
+		},
+		{
+			name: "key conflicts",
+			input: map[string]interface{}{
+				"user":          "user",
+				"user.name":     "username",
+				"user.password": "password",
+			},
+			expected: map[string]interface{}{
+				"user": "user",
+			},
+		},
+		{
+			name: "overwriting conflicts",
+			input: map[string]interface{}{
+				"order_id":             "order_id",
+				"user.document.id":     "document_id",
+				"user.document.number": "document_number",
+				"user.info.address":    "address",
+				"user.info.phone":      "phone",
+			},
+			expected: map[string]interface{}{
+				"order_id": "order_id",
+				"user": map[string]interface{}{
+					"document": map[string]interface{}{
+						"id":     "document_id",
+						"number": "document_number",
+					},
+					"info": map[string]interface{}{
+						"address": "address",
+						"phone":   "phone",
+					},
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			for range 100 { // need to exclude the impact of key order in the map on the test.
+				require.Equal(t, tt.expected, rutil.FlattenMap(tt.input))
+			}
+		})
+	}
+}