refactor: add SetValueFunc and case fold region values

internal/config/api/api.go

@@ -225,7 +225,7 @@ func SetConfigValue(key config.FieldKey, value interface{}) error {
 }
 
 // DeleteConfigValue deletes a config value for the given key.
-func DeleteConfigValue(key config.FieldKey, value interface{}) error {
+func DeleteConfigValue(key config.FieldKey) error {
 	return config.ConfigStore.DeleteKey(key)
 }
 

internal/config/command/command.go

@@ -38,7 +38,7 @@ The set command sets a persistent configuration value for the New Relic CLI.
 			log.Fatalf("%s is not a valid config field. valid values are %s", key, configAPI.GetValidConfigFieldKeys())
 		}
 
-		if err := configAPI.DeleteConfigValue(config.FieldKey(key), value); err != nil {
+		if err := configAPI.SetConfigValue(config.FieldKey(key), value); err != nil {
 			log.Fatal(err)
 		}
 

internal/config/config.go

@@ -19,7 +19,7 @@ const (
 	LogLevel           FieldKey = "loglevel"
 	PluginDir          FieldKey = "plugindir"
 	PreReleaseFeatures FieldKey = "prereleasefeatures"
-	SendUsageData      FieldKey = "sendusagedata"
+	SendUsageData      FieldKey = "sendUsageData"
 
 	DefaultProfileName = "default"
 
@@ -73,7 +73,8 @@ func InitializeCredentialsStore() {
 					region.US.String(),
 					region.EU.String(),
 				),
-				Default: region.US.String(),
+				Default:      region.US.String(),
+				SetValueFunc: ToLower(),
 			},
 			FieldDefinition{
 				Key:               AccountID,

internal/config/json_store.go

@@ -53,12 +53,21 @@ type FieldDefinition struct {
 	// is performed for the underlying value. If the func returns an error, the
 	// set operation will not succeed.
 	SetValidationFunc FieldValueValidationFunc
+
+	// SetValueFunc is a translation func that is run when a set operation
+	// is performed for the underlying value. The value provided will be run
+	// through the func provided and the resulting value will be set.
+	SetValueFunc FieldValueTranslationFunc
 }
 
 // FieldValueValidationFunc is a configurable validation func that will ensure a field
 // value conforms to some constraints before being set.
 type FieldValueValidationFunc func(key FieldKey, value interface{}) error
 
+// FieldValueTranslationFunc is a configurable translation func that will modify
+// a value before setting it in the underlying config instance.
+type FieldValueTranslationFunc func(key FieldKey, value interface{}) (interface{}, error)
+
 // IntGreaterThan is a FieldValueValidationFunc ins a validation func that ensures
 // the field value is an integer greater than 0.
 func IntGreaterThan(greaterThan int) func(key FieldKey, value interface{}) error {
@@ -117,6 +126,18 @@ func StringInStrings(caseSensitive bool, allowedValues ...string) func(key Field
 	}
 }
 
+// ToLower is a FieldValueTranslationFunc translation func that ensures the provided
+// value is case-folded to lowercase before writing to the underlying config.
+func ToLower() func(key FieldKey, value interface{}) (interface{}, error) {
+	return func(key FieldKey, value interface{}) (interface{}, error) {
+		if s, ok := value.(string); ok {
+			return strings.ToLower(s), nil
+		}
+
+		return nil, fmt.Errorf("the value %s provided for %s is not a string", value, key)
+	}
+}
+
 // JSONStoreOption is a func for supplying options when creating a new JSONStore.
 type JSONStoreOption func(*JSONStore) error
 
@@ -391,6 +412,15 @@ func (p *JSONStore) SetWithScope(scope string, key FieldKey, value interface{})
 			// use the case convention from the field definition
 			key = v.Key
 		}
+
+		if v.SetValueFunc != nil {
+			var err error
+			value, err = v.SetValueFunc(key, value)
+			if err != nil {
+				return err
+			}
+		}
+
 	} else if p.explicitValues {
 		return fmt.Errorf("key '%s' is not valid, valid keys are: %v", key, p.getConfigValueKeys())
 	}

internal/config/json_store_test.go

@@ -591,3 +591,26 @@ func TestStore_Set_ValidationFunc_StringInStrings_WrongType(t *testing.T) {
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "is not a string")
 }
+
+func TestStore_Set_ValueFunc_ToLower(t *testing.T) {
+	f, err := ioutil.TempFile("", "newrelic-cli.config_provider_test.*.json")
+	require.NoError(t, err)
+	defer f.Close()
+
+	p, err := NewJSONStore(
+		ConfigureFields(FieldDefinition{
+			Key:          "testString",
+			SetValueFunc: ToLower(),
+		}),
+		PersistToFile(f.Name()),
+	)
+	require.NoError(t, err)
+
+	err = p.Set("testString", "TEST_VALUE")
+	require.NoError(t, err)
+
+	v, err := p.GetString("testString")
+	require.NoError(t, err)
+
+	require.Equal(t, "test_value", v)
+}