Remove unused function

Extract common prefix function
Fix case of empty key for the scoped provider
Update prefix instead of recursing

config/provider.go

@@ -20,8 +20,6 @@
 
 package config
 
-import "fmt"
-
 // ConfigurationChangeCallback is called for updates of configuration data
 type ConfigurationChangeCallback func(key string, provider string, configdata interface{})
 
@@ -43,10 +41,6 @@ type Provider interface {
 	UnregisterChangeCallback(token string) error
 }
 
-func keyNotFound(key string) error {
-	return fmt.Errorf("couldn't find key %q", key)
-}
-
 // ScopedProvider defines recursive interface of providers based on the prefix
 type ScopedProvider struct {
 	Provider
@@ -55,38 +49,42 @@ type ScopedProvider struct {
 }
 
 // NewScopedProvider creates a child provider given a prefix
-func NewScopedProvider(prefix string, provider Provider) Provider {
+func NewScopedProvider(prefix string, provider Provider) *ScopedProvider {
 	return &ScopedProvider{provider, prefix}
 }
 
-// Get returns configuration value
-func (sp ScopedProvider) Get(key string) Value {
-	if sp.prefix != "" {
-		key = sp.prefix + "." + key
+func addPrefix(prefix, key string) string {
+	if prefix == "" {
+		return key
 	}
 
-	return sp.Provider.Get(key)
+	if key == "" {
+		return prefix
+	}
+
+	return prefix + "." + key
+}
+
+// Get returns configuration value
+func (sp ScopedProvider) Get(key string) Value {
+	return sp.Provider.Get(addPrefix(sp.prefix, key))
 }
 
 // Scope returns new scoped provider, given a prefix
 func (sp ScopedProvider) Scope(prefix string) Provider {
-	return NewScopedProvider(prefix, sp)
+	if prefix == "" {
+		return sp
+	}
+
+	return NewScopedProvider(addPrefix(sp.prefix, prefix), sp.Provider)
 }
 
-// RegisterChangeCallback registers the callback in the underling provider
+// RegisterChangeCallback registers the callback in the underlying provider
 func (sp ScopedProvider) RegisterChangeCallback(key string, callback ConfigurationChangeCallback) error {
-	if sp.prefix != "" {
-		key = sp.prefix + "." + key
-	}
-
-	return sp.Provider.RegisterChangeCallback(key, callback)
+	return sp.Provider.RegisterChangeCallback(addPrefix(sp.prefix, key), callback)
 }
 
-// UnregisterChangeCallback un registers a callback in the underling provider
+// UnregisterChangeCallback un registers a callback in the underlying provider
 func (sp ScopedProvider) UnregisterChangeCallback(key string) error {
-	if sp.prefix != "" {
-		key = sp.prefix + "." + key
-	}
-
-	return sp.Provider.UnregisterChangeCallback(key)
+	return sp.Provider.UnregisterChangeCallback(addPrefix(sp.prefix, key))
 }

config/provider_group_test.go

@@ -29,6 +29,7 @@ import (
 )
 
 func TestProviderGroup(t *testing.T) {
+	t.Parallel()
 	pg := NewProviderGroup("test-group", NewYAMLProviderFromBytes([]byte(`id: test`)))
 	assert.Equal(t, "test-group", pg.Name())
 	assert.Equal(t, "test", pg.Get("id").AsString())
@@ -38,12 +39,14 @@ func TestProviderGroup(t *testing.T) {
 }
 
 func TestProviderGroupScope(t *testing.T) {
+	t.Parallel()
 	data := map[string]interface{}{"hello.world": 42}
 	pg := NewProviderGroup("test-group", NewStaticProvider(data))
 	assert.Equal(t, 42, pg.Scope("hello").Get("world").AsInt())
 }
 
 func TestCallbacks_WithDynamicProvider(t *testing.T) {
+	t.Parallel()
 	data := map[string]interface{}{"hello.world": 42}
 	mock := NewProviderGroup("with-dynamic", NewStaticProvider(data))
 	mock = mock.(providerGroup).WithProvider(newMockDynamicProvider(data))
@@ -60,6 +63,7 @@ func TestCallbacks_WithDynamicProvider(t *testing.T) {
 }
 
 func TestCallbacks_WithoutDynamicProvider(t *testing.T) {
+	t.Parallel()
 	data := map[string]interface{}{"hello.world": 42}
 	mock := NewProviderGroup("with-dynamic", NewStaticProvider(data))
 	mock = mock.(providerGroup).WithProvider(NewStaticProvider(data))
@@ -69,6 +73,7 @@ func TestCallbacks_WithoutDynamicProvider(t *testing.T) {
 }
 
 func TestCallbacks_WithScopedProvider(t *testing.T) {
+	t.Parallel()
 	mock := &mockDynamicProvider{}
 	mock.Set("uber.fx", "go-lang")
 	scope := NewScopedProvider("uber", mock)
@@ -91,7 +96,27 @@ func TestCallbacks_WithScopedProvider(t *testing.T) {
 	val = scope.Get("fx").AsString()
 	require.Equal(t, "unregister works too!", val)
 	assert.Equal(t, 1, callCount)
+}
+
+func TestScope_WithScopedProvider(t *testing.T) {
+	t.Parallel()
+	mock := &mockDynamicProvider{}
+	mock.Set("uber.fx", "go-lang")
+	scope := NewScopedProvider("", mock)
+	require.Equal(t, "go-lang", scope.Get("uber.fx").AsString())
+	require.False(t, scope.Get("uber").HasValue())
+
+	base := scope.Scope("uber")
+	require.Equal(t, "go-lang", base.Get("fx").AsString())
+	require.False(t, base.Get("").HasValue())
+
+	uber := base.Scope("")
+	require.Equal(t, "go-lang", uber.Get("fx").AsString())
+	require.False(t, uber.Get("").HasValue())
 
+	fx := uber.Scope("fx")
+	require.Equal(t, "go-lang", fx.Get("").AsString())
+	require.False(t, fx.Get("fx").HasValue())
 }
 
 type mockDynamicProvider struct {