fix: unexpected error with --select-tag and multiple files

cmd/common.go

@@ -172,12 +172,13 @@ func determineSelectorTag(targetContent file.Content, config dump.Config) ([]str
 	if targetContent.Info != nil {
 		if len(targetContent.Info.SelectorTags) > 0 {
 			if len(config.SelectorTags) > 0 {
+				utils.RemoveDuplicates(&targetContent.Info.SelectorTags)
 				sort.Strings(config.SelectorTags)
 				sort.Strings(targetContent.Info.SelectorTags)
 				if !reflect.DeepEqual(config.SelectorTags, targetContent.Info.SelectorTags) {
-					return nil, fmt.Errorf(`tags specified in the state file and via --select-tags flag are different.
+					return nil, fmt.Errorf(`tags specified in the state file (%v) and via --select-tags flag (%v) are different.
 					decK expects tags to be specified in either via flag or via state file.
-					In case both are specified, they must match`)
+					In case both are specified, they must match`, targetContent.Info.SelectorTags, config.SelectorTags)
 				}
 				// Both present and equal, return whichever
 				return targetContent.Info.SelectorTags, nil

cmd/common_test.go

@@ -64,6 +64,24 @@ func TestDetermineSelectorTag(t *testing.T) {
 			want:    []string{"foo"},
 			wantErr: false,
 		},
+		{
+			name: "config has one tag and file has duplicates",
+			args: args{
+				dumpConfig:  dump.Config{SelectorTags: []string{"foo"}},
+				fileContent: file.Content{Info: &file.Info{SelectorTags: []string{"foo", "foo"}}},
+			},
+			want:    []string{"foo"},
+			wantErr: false,
+		},
+		{
+			name: "config has multiple tags and file has duplicates",
+			args: args{
+				dumpConfig:  dump.Config{SelectorTags: []string{"foo", "bar"}},
+				fileContent: file.Content{Info: &file.Info{SelectorTags: []string{"foo", "bar", "foo", "bar"}}},
+			},
+			want:    []string{"bar", "foo"},
+			wantErr: false,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

utils/utils.go

@@ -66,3 +66,24 @@ func CallGetAll(obj interface{}) (reflect.Value, error) {
 	result = reflect.ValueOf(entities)
 	return result, nil
 }
+
+func alreadyInSlice(elem string, slice []string) bool {
+	for _, s := range slice {
+		if s == elem {
+			return true
+		}
+	}
+	return false
+}
+
+// RemoveDuplicates removes duplicated elements from a slice.
+func RemoveDuplicates(slice *[]string) {
+	newSlice := []string{}
+	for _, s := range *slice {
+		if alreadyInSlice(s, newSlice) {
+			continue
+		}
+		newSlice = append(newSlice, s)
+	}
+	*slice = newSlice
+}