Add Scheme to MapProvider interface

This is another required step in order to support configuring map providers via the Builder.

Updates #4759

This is a breaking change, since adds a new func to an interface. It is hard to make this backwards compatible, and would like to move forward with this exception.

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

config/mapprovider.go

@@ -54,6 +54,9 @@ type MapProvider interface {
 	// Should never be called concurrently with itself or with Shutdown.
 	Retrieve(ctx context.Context, location string, watcher WatcherFunc) (Retrieved, error)
 
+	// Scheme returns the location scheme used by Retrieve.
+	Scheme() string
+
 	// Shutdown signals that the configuration for which this Provider was used to
 	// retrieve values is no longer in use and the Provider should close and release
 	// any resources that it may have created.

config/mapprovider/envmapprovider/mapprovider.go

@@ -51,6 +51,10 @@ func (emp *mapProvider) Retrieve(_ context.Context, location string, _ config.Wa
 	return config.Retrieved{Map: config.NewMapFromStringMap(data)}, nil
 }
 
+func (fmp *mapProvider) Scheme() string {
+	return schemeName
+}
+
 func (*mapProvider) Shutdown(context.Context) error {
 	return nil
 }

config/mapprovider/filemapprovider/mapprovider.go

@@ -66,6 +66,10 @@ func (fmp *mapProvider) Retrieve(_ context.Context, location string, _ config.Wa
 	return config.Retrieved{Map: config.NewMapFromStringMap(data)}, nil
 }
 
+func (fmp *mapProvider) Scheme() string {
+	return schemeName
+}
+
 func (*mapProvider) Shutdown(context.Context) error {
 	return nil
 }

config/mapprovider/yamlmapprovider/mapprovider.go

@@ -53,6 +53,10 @@ func (s *mapProvider) Retrieve(_ context.Context, location string, _ config.Watc
 	return config.Retrieved{Map: config.NewMapFromStringMap(data)}, nil
 }
 
+func (fmp *mapProvider) Scheme() string {
+	return schemeName
+}
+
 func (s *mapProvider) Shutdown(context.Context) error {
 	return nil
 }

service/config_provider.go

@@ -106,11 +106,7 @@ func MustNewConfigProvider(
 func MustNewDefaultConfigProvider(configLocations []string, properties []string) ConfigProvider {
 	return MustNewConfigProvider(
 		configLocations,
-		map[string]config.MapProvider{
-			"file": filemapprovider.New(),
-			"env":  envmapprovider.New(),
-			"yaml": yamlmapprovider.New(),
-		},
+		makeConfigMapProviderMap(filemapprovider.New(), envmapprovider.New(), yamlmapprovider.New()),
 		[]config.MapConverterFunc{
 			configmapprovider.NewOverwritePropertiesConverter(properties),
 			configmapprovider.NewExpandConverter(),
@@ -222,3 +218,11 @@ func (cm *configProvider) mergeRetrieve(ctx context.Context) (*config.Retrieved,
 		},
 	}, nil
 }
+
+func makeConfigMapProviderMap(providers ...config.MapProvider) map[string]config.MapProvider {
+	ret := make(map[string]config.MapProvider, len(providers))
+	for _, provider := range providers {
+		ret[provider.Scheme()] = provider
+	}
+	return ret
+}