[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

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))
+			}
+		})
+	}
+}