Implement struct fx.Annotated to inject named values without relying on fx.Out

annotated.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2018 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package fx
+
+type Annotated struct {
+	Name string
+	Fn   interface{}
+}

annotated_test.go

@@ -0,0 +1,39 @@
+package fx_test
+
+import (
+	"testing"
+	"go.uber.org/fx/fxtest"
+	"github.com/stretchr/testify/assert"
+	"go.uber.org/fx"
+)
+
+func TestAnnotated(t *testing.T) {
+	type a struct {
+		name string
+	}
+
+	type in struct {
+		fx.In
+
+		A *a `name:"foo"`
+	}
+	newA := func() *a {
+		return &a{name: "foo"}
+	}
+
+	t.Run("Provided", func(t *testing.T) {
+		app := fxtest.New(t,
+			fx.Provide(
+				fx.Annotated{
+					Name: "foo",
+					Fn:   newA,
+				},
+			),
+			fx.Invoke(func(in in) {
+				assert.NotNil(t, in.A, "expected in.A to be injected")
+				assert.Equal(t, "foo", in.A.name, "expected to get a type 'a' of name 'foo'")
+			}),
+		)
+		app.RequireStart().RequireStop()
+	})
+}

app.go

@@ -404,6 +404,13 @@ func (app *App) provide(constructor interface{}) {
 		return
 	}
 
+	if a, ok := constructor.(Annotated); ok {
+		if err := app.container.Provide(a.Fn, dig.Name(a.Name)); err != nil {
+			app.err = err
+		}
+		return
+	}
+
 	if err := app.container.Provide(constructor); err != nil {
 		app.err = err
 	}

glide.yaml

@@ -3,7 +3,7 @@ import:
 - package: go.uber.org/multierr
   version: ^1
 - package: go.uber.org/dig
-  version: ^1
+  version: master
 testImport:
 - package: github.com/stretchr/testify
   version: ^1

version.go

@@ -21,4 +21,4 @@
 package fx
 
 // Version is exported for runtime compatibility checks.
-const Version = "1.7.0"
+const Version = "1.8.0"