Add option for naming decorator outputs

decorate.go

@@ -83,7 +83,9 @@ func newDecoratorNode(dcor interface{}, s *Scope, opts decorateOptions) (*decora
 		return nil, err
 	}
 
-	rl, err := newResultList(dtype, resultOptions{})
+	rl, err := newResultList(dtype, resultOptions{
+		Name: opts.Name,
+	})
 	if err != nil {
 		return nil, err
 	}
@@ -171,11 +173,43 @@ type DecorateOption interface {
 }
 
 type decorateOptions struct {
+	Name           string
 	Info           *DecorateInfo
 	Callback       Callback
 	BeforeCallback BeforeCallback
 }
 
+// Name is a ProvideOption that specifies that all values produced by a
+// constructor should have the given name. See also the package documentation
+// about Named Values.
+//
+// Given,
+//
+//	func NewReadOnlyConnection(...) (*Connection, error)
+//	func NewReadWriteConnection(...) (*Connection, error)
+//
+// The following will provide two connections to the container: one under the
+// name "ro" and the other under the name "rw".
+//
+//	c.Provide(NewReadOnlyConnection, dig.Name("ro"))
+//	c.Provide(NewReadWriteConnection, dig.Name("rw"))
+//
+// This option cannot be provided for constructors which produce result
+// objects.
+func DecorateName(name string) DecorateOption {
+	return decorateNameOption(name)
+}
+
+type decorateNameOption string
+
+func (o decorateNameOption) String() string {
+	return fmt.Sprintf("DecorateName(%q)", string(o))
+}
+
+func (o decorateNameOption) apply(opt *decorateOptions) {
+	opt.Name = string(o)
+}
+
 // FillDecorateInfo is a DecorateOption that writes info on what Dig was
 // able to get out of the provided decorator into the provided DecorateInfo.
 func FillDecorateInfo(info *DecorateInfo) DecorateOption {

decorate_test.go

@@ -81,6 +81,30 @@ func TestDecorateSuccess(t *testing.T) {
 		assert.Equal(t, "*dig_test.A", info.Outputs[0].String())
 	})
 
+	t.Run("simple decorate with name", func(t *testing.T) {
+		t.Parallel()
+		type A struct {
+			name string
+		}
+
+		c := digtest.New(t)
+		c.RequireProvide(func() *A { return &A{name: "A"} }, dig.Name("a"))
+
+		type B struct {
+			dig.In
+			A *A `name:"a"`
+		}
+
+		c.RequireInvoke(func(b B) {
+			assert.Equal(t, "A", b.A.name, "expected name to not be decorated yet.")
+		})
+
+		c.RequireDecorate(func(b B) *A { return &A{name: b.A.name + "'"} }, dig.DecorateName("a"))
+		c.RequireInvoke(func(b B) {
+			assert.Equal(t, "A'", b.A.name, "expected name to equal decorated name.")
+		})
+	})
+
 	t.Run("simple decorate a provider from child scope", func(t *testing.T) {
 		t.Parallel()
 		type A struct {