do not update group list if the member group list is not changed

pkg/looker/resource_group_membership.go

@@ -108,6 +108,16 @@ func resourceGroupMembershipRead(ctx context.Context, d *schema.ResourceData, m
 	return nil
 }
 
+func getGroupIDs(m interface{}, groupId string) ([]string, error) {
+	client := m.(*apiclient.LookerSDK)
+	groups, err := client.AllGroupGroups(groupId, "", nil) // todo: imeplement paging
+	if err != nil {
+		return nil, err
+	}
+
+	return flattenGroupIDs(groups), nil
+}
+
 func resourceGroupMembershipUpdate(ctx context.Context, d *schema.ResourceData, m interface{}) diag.Diagnostics {
 	targetGroupID := d.Id()
 
@@ -122,21 +132,30 @@ func resourceGroupMembershipUpdate(ctx context.Context, d *schema.ResourceData,
 	if err != nil {
 		return diag.FromErr(err)
 	}
-
-	err = removeAllGroupsFromGroup(m, targetGroupID)
+	groupIDs := expandStringListFromSet(d.Get("group_ids"))
+	actualGroupIDs, err := getGroupIDs(m, targetGroupID)
 	if err != nil {
 		return diag.FromErr(err)
 	}
+	updateGroupsFromGroupRequired := differentStringSlices(actualGroupIDs, groupIDs)
+
+	if updateGroupsFromGroupRequired {
+		err = removeAllGroupsFromGroup(m, targetGroupID)
+		if err != nil {
+			return diag.FromErr(err)
+		}
+	}
 
 	err = addGroupUsers(m, targetGroupID, userIDs)
 	if err != nil {
 		return diag.FromErr(err)
 	}
 
-	groupIDs := expandStringListFromSet(d.Get("group_ids"))
-	err = addGroupGroups(m, targetGroupID, groupIDs)
-	if err != nil {
-		return diag.FromErr(err)
+	if updateGroupsFromGroupRequired {
+		err = addGroupGroups(m, targetGroupID, groupIDs)
+		if err != nil {
+			return diag.FromErr(err)
+		}
 	}
 
 	return resourceGroupMembershipRead(ctx, d, m)

pkg/looker/util.go

@@ -61,3 +61,20 @@ func hash(val interface{}) string {
 	sha := sha256.Sum256([]byte(val.(string)))
 	return hex.EncodeToString(sha[:])
 }
+
+func differentStringSlices(a, b []string) bool {
+	if len(a) != len(b) {
+		return true
+	}
+	counts := make(map[string]int)
+	for _, item := range a {
+		counts[item]++
+	}
+	for _, item := range b {
+		counts[item]--
+		if counts[item] < 0 {
+			return true
+		}
+	}
+	return false
+}

pkg/looker/util_test.go

@@ -6,6 +6,37 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestDifferentStringSlices(t *testing.T) {
+	tests := map[string]struct {
+		a       []string
+		b       []string
+		wantRes bool
+	}{
+		"same slice": {
+			a:       []string{"a", "b", "c"},
+			b:       []string{"a", "b", "c"},
+			wantRes: false,
+		},
+		"different slice": {
+			a:       []string{"a", "b", "c"},
+			b:       []string{"a", "b", "d"},
+			wantRes: true,
+		},
+		"one slice is empty": {
+			a:       []string{},
+			b:       []string{"a", "b", "c"},
+			wantRes: true,
+		},
+	}
+
+	for key, tt := range tests {
+		t.Run(key, func(t *testing.T) {
+			actual := differentStringSlices(tt.a, tt.b)
+			assert.Equal(t, tt.wantRes, actual)
+		})
+	}
+}
+
 func TestBuildTwoPartID(t *testing.T) {
 	tests := map[string]struct {
 		a       string