Bind: takes a pointer for the second argument (#152)

internal/wire/parse.go

@@ -337,7 +337,7 @@ func Load(ctx context.Context, wd string, env []string, patterns []string) (*Inf
 }
 
 // load typechecks the packages that match the given patterns and
-// includes source for all transitive dependencies.  The patterns are
+// includes source for all transitive dependencies. The patterns are
 // defined by the underlying build system. For the go tool, this is
 // described at https://golang.org/cmd/go/#hdr-Package_lists_and_patterns
 //
@@ -860,25 +860,39 @@ func processBind(fset *token.FileSet, info *types.Info, call *ast.CallExpr) (*If
 	// Assumes that call.Fun is wire.Bind.
 
 	if len(call.Args) != 2 {
-		return nil, notePosition(fset.Position(call.Pos()), errors.New("call to Bind takes exactly two arguments"))
+		return nil, notePosition(fset.Position(call.Pos()),
+			errors.New("call to Bind takes exactly two arguments"))
 	}
 	// TODO(light): Verify that arguments are simple expressions.
 	ifaceArgType := info.TypeOf(call.Args[0])
 	ifacePtr, ok := ifaceArgType.(*types.Pointer)
 	if !ok {
-		return nil, notePosition(fset.Position(call.Pos()), fmt.Errorf("first argument to Bind must be a pointer to an interface type; found %s", types.TypeString(ifaceArgType, nil)))
+		return nil, notePosition(fset.Position(call.Pos()),
+			fmt.Errorf("first argument to Bind must be a pointer to an interface type; found %s", types.TypeString(ifaceArgType, nil)))
 	}
 	iface := ifacePtr.Elem()
 	methodSet, ok := iface.Underlying().(*types.Interface)
 	if !ok {
-		return nil, notePosition(fset.Position(call.Pos()), fmt.Errorf("first argument to Bind must be a pointer to an interface type; found %s", types.TypeString(ifaceArgType, nil)))
+		return nil, notePosition(fset.Position(call.Pos()),
+			fmt.Errorf("first argument to Bind must be a pointer to an interface type; found %s", types.TypeString(ifaceArgType, nil)))
 	}
+
 	provided := info.TypeOf(call.Args[1])
+	if bindShouldUsePointer(info, call) {
+		providedPtr, ok := provided.(*types.Pointer)
+		if !ok {
+			return nil, notePosition(fset.Position(call.Args[0].Pos()),
+				fmt.Errorf("second argument to Bind must be a pointer or a pointer to a pointer; found %s", types.TypeString(provided, nil)))
+		}
+		provided = providedPtr.Elem()
+	}
 	if types.Identical(iface, provided) {
-		return nil, notePosition(fset.Position(call.Pos()), errors.New("cannot bind interface to itself"))
+		return nil, notePosition(fset.Position(call.Pos()),
+			errors.New("cannot bind interface to itself"))
 	}
 	if !types.Implements(provided, methodSet) {
-		return nil, notePosition(fset.Position(call.Pos()), fmt.Errorf("%s does not implement %s", types.TypeString(provided, nil), types.TypeString(iface, nil)))
+		return nil, notePosition(fset.Position(call.Pos()),
+			fmt.Errorf("%s does not implement %s", types.TypeString(provided, nil), types.TypeString(iface, nil)))
 	}
 	return &IfaceBinding{
 		Pos:      call.Pos(),
@@ -1185,3 +1199,13 @@ func (pt ProvidedType) Field() *Field {
 	}
 	return pt.f
 }
+
+// bindShouldUsePointer loads the wire package the user is importing from their
+// injector. The call is a wire marker function call.
+func bindShouldUsePointer(info *types.Info, call *ast.CallExpr) bool {
+	// These type assertions should not fail, otherwise panic.
+	fun := call.Fun.(*ast.SelectorExpr)                 // wire.Bind
+	pkgName := fun.X.(*ast.Ident)                       // wire
+	wireName := info.ObjectOf(pkgName).(*types.PkgName) // wire package
+	return wireName.Imported().Scope().Lookup("bindToUsePointer") != nil
+}

internal/wire/testdata/BindInjectorArg/foo/foo.go

@@ -19,7 +19,7 @@ import (
 )
 
 func main() {
-	fmt.Println(inject(&Foo{"hello"}).Name)
+	fmt.Println(inject(Foo{"hello"}).Name)
 }
 
 type Fooer interface {
@@ -30,7 +30,7 @@ type Foo struct {
 	f string
 }
 
-func (f *Foo) Foo() string {
+func (f Foo) Foo() string {
 	return f.f
 }
 

internal/wire/testdata/BindInjectorArg/foo/wire.go

@@ -20,11 +20,10 @@ import (
 	"github.com/google/wire"
 )
 
-func inject(foo *Foo) *Bar {
+func inject(foo Foo) *Bar {
-	// Currently fails because wire.Bind can't see injector args (#547).
 	wire.Build(
 		NewBar,
-		wire.Bind(new(Fooer), &Foo{}),
+		wire.Bind(new(Fooer), new(Foo)),
 	)
 	return nil
 }

internal/wire/testdata/BindInjectorArg/want/wire_gen.go

@@ -7,7 +7,7 @@ package main
 
 // Injectors from wire.go:
 
-func inject(foo *Foo) *Bar {
+func inject(foo Foo) *Bar {
 	bar := NewBar(foo)
 	return bar
 }

internal/wire/testdata/BindInjectorArgPointer/foo/foo.go

@@ -0,0 +1,43 @@
+// Copyright 2019 The Wire Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	fmt.Println(inject(&Foo{"hello"}).Name)
+}
+
+type Fooer interface {
+	Foo() string
+}
+
+type Foo struct {
+	f string
+}
+
+func (f *Foo) Foo() string {
+	return f.f
+}
+
+type Bar struct {
+	Name string
+}
+
+func NewBar(fooer Fooer) *Bar {
+	return &Bar{Name: fooer.Foo()}
+}

internal/wire/testdata/BindInjectorArgPointer/foo/wire.go

@@ -0,0 +1,29 @@
+// Copyright 2019 The Wire Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+//+build wireinject
+
+package main
+
+import (
+	"github.com/google/wire"
+)
+
+func inject(foo *Foo) *Bar {
+	wire.Build(
+		NewBar,
+		wire.Bind(new(Fooer), new(*Foo)),
+	)
+	return nil
+}

internal/wire/testdata/BindInjectorArgPointer/pkg

@@ -0,0 +1 @@
+example.com/foo

internal/wire/testdata/BindInjectorArgPointer/want/program_out.txt

@@ -0,0 +1 @@
+hello

internal/wire/testdata/BindInjectorArgPointer/want/wire_gen.go

@@ -0,0 +1,13 @@
+// Code generated by Wire. DO NOT EDIT.
+
+//go:generate wire
+//+build !wireinject
+
+package main
+
+// Injectors from wire.go:
+
+func inject(foo *Foo) *Bar {
+	bar := NewBar(foo)
+	return bar
+}

internal/wire/testdata/BindInterfaceWithValue/foo/wire.go

@@ -26,7 +26,7 @@ import (
 func inject() io.Writer {
 	wire.Build(
 		wire.Value(os.Stdout),
-		wire.Bind(new(io.Writer), new(os.File)),
+		wire.Bind(new(io.Writer), new(*os.File)),
 	)
 	return nil
 }

internal/wire/testdata/ExampleWithMocks/foo/foo.go

@@ -75,7 +75,7 @@ var mockAppSet = wire.NewSet(
 	// For each mocked dependency, add a provider and use wire.Bind to bind
 	// the concrete type to the relevant interface.
 	newMockTimer,
-	wire.Bind(new(timer), new(mockTimer)),
+	wire.Bind(new(timer), new(*mockTimer)),
 )
 
 type timer interface {

internal/wire/testdata/ImportedInterfaceBinding/bar/bar.go

@@ -39,4 +39,4 @@ func provideBar() *Bar {
 
 var Set = wire.NewSet(
 	provideBar,
-	wire.Bind((*foo.Fooer)(nil), (*Bar)(nil)))
+	wire.Bind(new(foo.Fooer), new(*Bar)))

internal/wire/testdata/InterfaceBinding/foo/foo.go

@@ -42,4 +42,4 @@ func provideBar() *Bar {
 
 var Set = wire.NewSet(
 	provideBar,
-	wire.Bind((*Fooer)(nil), (*Bar)(nil)))
+	wire.Bind(new(Fooer), new(*Bar)))

internal/wire/testdata/InterfaceBindingDoesntImplement/foo/wire.go

@@ -22,6 +22,6 @@ import (
 
 func injectFooer() Fooer {
 	// wrong: string doesn't implement Fooer.
-	wire.Build(wire.Bind((*Fooer)(nil), "foo"))
+	wire.Build(wire.Bind(new(Fooer), new(string)))
 	return nil
 }

internal/wire/testdata/InterfaceBindingNotEnoughArgs/foo/wire.go

@@ -22,6 +22,6 @@ import (
 
 func injectFooer() Fooer {
 	// wrong: wire.Bind requires 2 args.
-	wire.Build(wire.Bind((*Fooer)(nil)))
+	wire.Build(wire.Bind(new(Fooer)))
 	return nil
 }

internal/wire/testdata/InterfaceBindingReuse/foo/wire.go

@@ -24,7 +24,7 @@ func injectFooBar() FooBar {
 	wire.Build(
 		provideBar,
 		provideFooBar,
-		wire.Bind((*Fooer)(nil), (*Bar)(nil)),
+		wire.Bind(new(Fooer), new(*Bar)),
 	)
 	return FooBar{}
 }

internal/wire/testdata/MultipleBindings/foo/wire.go

@@ -49,5 +49,5 @@ func injectDuplicateValues() Foo {
 
 func injectDuplicateInterface() Bar {
 	// fail: provideBar and wire.Bind both provide Bar.
-	panic(wire.Build(provideBar, wire.Bind(new(Bar), strings.NewReader("hello"))))
+	panic(wire.Build(provideBar, wire.Bind(new(Bar), new(*strings.Reader))))
 }

internal/wire/testdata/ProviderSetBindingMissingConcreteType/foo/foo.go

@@ -44,6 +44,6 @@ var (
 	// From the user guide:
 	// Any set that includes an interface binding must also have a provider in
 	// the same set that provides the concrete type.
-	setB = wire.NewSet(wire.Bind(new(fooer), new(foo)))
+	setB = wire.NewSet(wire.Bind(new(fooer), new(*foo)))
 	setC = wire.NewSet(setA, setB)
 )

internal/wire/testdata/UnusedProviders/foo/wire.go

@@ -22,14 +22,14 @@ import (
 
 func injectBar() Bar {
 	wire.Build(
-		provideFoo,                            // needed as input for provideBar
+		provideFoo,                       // needed as input for provideBar
-		provideBar,                            // needed for Bar
+		provideBar,                       // needed for Bar
-		partiallyUsedSet,                      // 1/2 providers in the set are needed
+		partiallyUsedSet,                 // 1/2 providers in the set are needed
-		provideUnused,                         // not needed -> error
+		provideUnused,                    // not needed -> error
-		wire.Value("unused"),                  // not needed -> error
+		wire.Value("unused"),             // not needed -> error
-		unusedSet,                             // nothing in set is needed -> error
+		unusedSet,                        // nothing in set is needed -> error
-		wire.Bind((*Fooer)(nil), (*Foo)(nil)), // binding to Fooer is not needed -> error
+		wire.Bind(new(Fooer), new(*Foo)), // binding to Fooer is not needed -> error
-		wire.FieldsOf(new(S), "Cfg"),          // S.Cfg not needed -> error
+		wire.FieldsOf(new(S), "Cfg"),     // S.Cfg not needed -> error
 	)
 	return 0
 }

wire.go

@@ -93,9 +93,9 @@ func Build(...interface{}) string {
 // A Binding maps an interface to a concrete type.
 type Binding struct{}
 
-// Bind declares that a concrete type should be used to satisfy a
+// Bind declares that a concrete type should be used to satisfy a dependency on
-// dependency on the type of iface, which must be a pointer to an
+// the type of iface. iface must be a pointer to an interface type, to must be a
-// interface type.
+// pointer to a concrete type.
 //
 // Example:
 //
@@ -108,12 +108,16 @@ type Binding struct{}
 //	func (MyFoo) Foo() {}
 //
 //	var MySet = wire.NewSet(
-//		MyFoo{},
+//		wire.Struct(new(MyFoo))
 //		wire.Bind(new(Fooer), new(MyFoo)))
 func Bind(iface, to interface{}) Binding {
 	return Binding{}
 }
 
+// bindToUsePointer is detected by the wire tool to indicate that Bind's second argument should take a pointer.
+// See https://github.com/google/wire/issues/120 for details.
+const bindToUsePointer = true
+
 // A ProvidedValue is an expression that is copied to the generated injector.
 type ProvidedValue struct{}