fix: improve handling of empty default boolean values in config binding (#258)

Author: nexus49

config/config.go

@@ -157,11 +157,15 @@ func traverseStruct(value reflect.Value, flagSet *pflag.FlagSet, prefix string)
 				flagSet.Int(prefix+tag, i, description)
 			}
 		case reflect.Bool:
-			b, err := strconv.ParseBool(defaultStrValue)
-			if err != nil {
-				return err
+			var defaultBoolValue bool
+			if defaultStrValue != "" {
+				b, err := strconv.ParseBool(defaultStrValue)
+				if err != nil {
+					return err
+				}
+				defaultBoolValue = b
 			}
-			flagSet.Bool(prefix+tag, b, description)
+			flagSet.Bool(prefix+tag, defaultBoolValue, description)
 		default:
 			return fmt.Errorf("unsupported field type %s for field %s", fieldValue.Kind(), field.Name)
 		}

config/config_test.go

@@ -118,6 +118,25 @@ func TestBindConfigToFlagsWrongTypeBool(t *testing.T) {
 	assert.Error(t, err)
 }
 
+func TestBindConfigToFlagsEmptyDefaultBool(t *testing.T) {
+	type test struct {
+		CustomFlagInt bool `mapstructure:"custom-flag" default:""`
+	}
+
+	testStruct := test{}
+
+	v := viper.New()
+
+	cmd := &cobra.Command{}
+	err := config.BindConfigToFlags(v, cmd, &testStruct) // assuming this binds flags
+	assert.NoError(t, err)
+
+	boolFlag := cmd.Flags().Lookup("custom-flag")
+	assert.NotNil(t, boolFlag)
+	assert.Equal(t, "Set the custom-flag", boolFlag.Usage)
+	assert.Equal(t, "false", boolFlag.DefValue)
+}
+
 func TestBindConfigToFlagsWrongType(t *testing.T) {
 	type test struct {
 		CustomFlagInt byte `mapstructure:"custom-flag" default:"abc"`