internal/wire: support specifying struct fields to inject (#147)

Added wire.Struct function and deprecate old form.

Updates #36

internal/wire/parse.go

@@ -21,6 +21,7 @@ import (
 	"go/ast"
 	"go/token"
 	"go/types"
+	"os"
 	"strconv"
 	"strings"
 
@@ -550,6 +551,12 @@ func (oc *objectCache) processExpr(info *types.Info, pkgPath string, expr ast.Ex
 				return nil, []error{notePosition(exprPos, err)}
 			}
 			return v, nil
+		case "Struct":
+			s, err := processStructProvider(oc.fset, info, call)
+			if err != nil {
+				return nil, []error{notePosition(exprPos, err)}
+			}
+			return s, nil
 		case "FieldsOf":
 			v, err := processFieldsOf(oc.fset, info, call)
 			if err != nil {
@@ -561,7 +568,7 @@ func (oc *objectCache) processExpr(info *types.Info, pkgPath string, expr ast.Ex
 		}
 	}
 	if tn := structArgType(info, expr); tn != nil {
-		p, errs := processStructProvider(oc.fset, tn)
+		p, errs := processStructLiteralProvider(oc.fset, tn)
 		if len(errs) > 0 {
 			return nil, notePositionAll(exprPos, errs)
 		}
@@ -733,9 +740,11 @@ func funcOutput(sig *types.Signature) (outputSignature, error) {
 	}
 }
 
-// processStructProvider creates a provider for a named struct type.
+// processStructLiteralProvider creates a provider for a named struct type.
 // It produces pointer and non-pointer variants via two values in Out.
-func processStructProvider(fset *token.FileSet, typeName *types.TypeName) (*Provider, []error) {
+//
+// This is a copy of the old processStructProvider, which is deprecated now.
+func processStructLiteralProvider(fset *token.FileSet, typeName *types.TypeName) (*Provider, []error) {
 	out := typeName.Type()
 	st, ok := out.Underlying().(*types.Struct)
 	if !ok {
@@ -743,6 +752,10 @@ func processStructProvider(fset *token.FileSet, typeName *types.TypeName) (*Prov
 	}
 
 	pos := typeName.Pos()
+	fmt.Fprintf(os.Stderr,
+		"Deprecated: %v, see https://godoc.org/github.com/google/wire#Struct for more information.",
+		notePosition(fset.Position(pos),
+			fmt.Errorf("using struct literal to inject %s, use wire.Struct instead", typeName.Type())))
 	provider := &Provider{
 		Pkg:      typeName.Pkg(),
 		Name:     typeName.Name(),
@@ -766,6 +779,82 @@ func processStructProvider(fset *token.FileSet, typeName *types.TypeName) (*Prov
 	return provider, nil
 }
 
+// processStructProvider creates a provider for a named struct type.
+// It produces pointer and non-pointer variants via two values in Out.
+func processStructProvider(fset *token.FileSet, info *types.Info, call *ast.CallExpr) (*Provider, error) {
+	// Assumes that call.Fun is wire.Struct.
+
+	if len(call.Args) < 1 {
+		return nil, notePosition(fset.Position(call.Pos()),
+			errors.New("call to Struct must specify the struct to be injected"))
+	}
+	const firstArgReqFormat = "first argument to Struct must be a pointer to a named struct; found %s"
+	structType := info.TypeOf(call.Args[0])
+	structPtr, ok := structType.(*types.Pointer)
+	if !ok {
+		return nil, notePosition(fset.Position(call.Pos()),
+			fmt.Errorf(firstArgReqFormat, types.TypeString(structType, nil)))
+	}
+
+	st, ok := structPtr.Elem().Underlying().(*types.Struct)
+	if !ok {
+		return nil, notePosition(fset.Position(call.Pos()),
+			fmt.Errorf(firstArgReqFormat, types.TypeString(st, nil)))
+	}
+
+	stExpr := call.Args[0].(*ast.CallExpr)
+	typeName := qualifiedIdentObject(info, stExpr.Args[0]) // should be either an identifier or selector
+	provider := &Provider{
+		Pkg:      typeName.Pkg(),
+		Name:     typeName.Name(),
+		Pos:      typeName.Pos(),
+		IsStruct: true,
+		Out:      []types.Type{structPtr.Elem(), structPtr},
+	}
+	if allFields(call) {
+		provider.Args = make([]ProviderInput, st.NumFields())
+		for i := 0; i < st.NumFields(); i++ {
+			f := st.Field(i)
+			provider.Args[i] = ProviderInput{
+				Type:      f.Type(),
+				FieldName: f.Name(),
+			}
+		}
+	} else {
+		provider.Args = make([]ProviderInput, len(call.Args)-1)
+		for i := 1; i < len(call.Args); i++ {
+			v, err := checkField(call.Args[i], st)
+			if err != nil {
+				return nil, notePosition(fset.Position(call.Pos()), err)
+			}
+			provider.Args[i-1] = ProviderInput{
+				Type:      v.Type(),
+				FieldName: v.Name(),
+			}
+		}
+	}
+	for i := 0; i < len(provider.Args); i++ {
+		for j := 0; j < i; j++ {
+			if types.Identical(provider.Args[i].Type, provider.Args[j].Type) {
+				f := st.Field(j)
+				return nil, notePosition(fset.Position(f.Pos()), fmt.Errorf("provider struct has multiple fields of type %s", types.TypeString(provider.Args[j].Type, nil)))
+			}
+		}
+	}
+	return provider, nil
+}
+
+func allFields(call *ast.CallExpr) bool {
+	if len(call.Args) != 2 {
+		return false
+	}
+	b, ok := call.Args[1].(*ast.BasicLit)
+	if !ok {
+		return false
+	}
+	return strings.EqualFold(strconv.Quote("*"), b.Value)
+}
+
 // processBind creates an interface binding from a wire.Bind call.
 func processBind(fset *token.FileSet, info *types.Info, call *ast.CallExpr) (*IfaceBinding, error) {
 	// Assumes that call.Fun is wire.Bind.

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

@@ -51,8 +51,8 @@ func main() {
 
 // appSet is a provider set for creating a real app.
 var appSet = wire.NewSet(
-	app{},
-	greeter{},
+	wire.Struct(new(app), "*"),
+	wire.Struct(new(greeter), "*"),
 	wire.InterfaceValue(new(timer), realTime{}),
 )
 
@@ -61,17 +61,17 @@ var appSet = wire.NewSet(
 // arguments to the injector.
 // It is used for Approach A.
 var appSetWithoutMocks = wire.NewSet(
-	app{},
-	greeter{},
+	wire.Struct(new(app), "*"),
+	wire.Struct(new(greeter), "*"),
 )
 
 // mockAppSet is a provider set for creating a mocked app, including the mocked
 // dependencies.
 // It is used for Approach B.
 var mockAppSet = wire.NewSet(
-	app{},
-	greeter{},
-	appWithMocks{},
+	wire.Struct(new(app), "*"),
+	wire.Struct(new(greeter), "*"),
+	wire.Struct(new(appWithMocks), "*"),
 	// For each mocked dependency, add a provider and use wire.Bind to bind
 	// the concrete type to the relevant interface.
 	newMockTimer,

internal/wire/testdata/FieldsOfImportedStruct/main/wire.go

@@ -27,7 +27,7 @@ import (
 
 func newBazService(*baz.Config) *baz.Service {
 	wire.Build(
-		baz.Service{},
+		wire.Struct(new(baz.Service), "*"),
 		wire.FieldsOf(
 			new(*baz.Config),
 			"Foo",

internal/wire/testdata/FieldsOfValueStruct/main/wire.go

@@ -27,7 +27,7 @@ import (
 
 func newBazService() *baz.Service {
 	wire.Build(
-		baz.Service{},
+		wire.Struct(new(baz.Service), "*"),
 		wire.Value(&baz.Config{
 			Foo: &foo.Config{1},
 			Bar: &bar.Config{2},

internal/wire/testdata/MultipleSimilarPackages/main/wire.go

@@ -43,7 +43,7 @@ func (m *MainService) String() string {
 
 func newMainService(MainConfig) *MainService {
 	wire.Build(
-		MainService{},
+		wire.Struct(new(MainService), "Foo", "Bar", "baz"),
 		wire.FieldsOf(
 			new(MainConfig),
 			"Foo",

internal/wire/testdata/Struct/foo/foo.go

@@ -22,7 +22,9 @@ import (
 
 func main() {
 	fb := injectFooBar()
+	pfb := injectPartFooBar()
 	fmt.Println(fb.Foo, fb.Bar)
+	fmt.Println(pfb.Foo, pfb.Bar)
 }
 
 type Foo int
@@ -42,6 +44,11 @@ func provideBar() Bar {
 }
 
 var Set = wire.NewSet(
-	FooBar{},
+	wire.Struct(new(FooBar), "*"),
 	provideFoo,
 	provideBar)
+
+var PartSet = wire.NewSet(
+	wire.Struct(new(FooBar), "Foo"),
+	provideFoo,
+)

internal/wire/testdata/Struct/foo/wire.go

@@ -24,3 +24,8 @@ func injectFooBar() FooBar {
 	wire.Build(Set)
 	return FooBar{}
 }
+
+func injectPartFooBar() FooBar {
+	wire.Build(PartSet)
+	return FooBar{}
+}

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

@@ -1 +1,2 @@
 41 1
+41 0

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

@@ -16,3 +16,11 @@ func injectFooBar() FooBar {
 	}
 	return fooBar
 }
+
+func injectPartFooBar() FooBar {
+	foo := provideFoo()
+	fooBar := FooBar{
+		Foo: foo,
+	}
+	return fooBar
+}

internal/wire/testdata/StructPointer/foo/foo.go

@@ -45,6 +45,6 @@ func provideBar() Bar {
 }
 
 var Set = wire.NewSet(
-	FooBar{},
+	wire.Struct(new(FooBar), "*"),
 	provideFoo,
 	provideBar)

internal/wire/testdata/StructPointer/foo/wire.go

@@ -26,6 +26,6 @@ func injectFooBar() *FooBar {
 }
 
 func injectEmptyStruct() *Empty {
-	wire.Build(Empty{})
+	wire.Build(wire.Struct(new(Empty)))
 	return nil
 }

wire.go

@@ -29,9 +29,9 @@ package wire
 type ProviderSet struct{}
 
 // NewSet creates a new provider set that includes the providers in its
-// arguments. Each argument is a function value, a struct (zero) value, a
-// provider set, a call to Bind, a call to Value, a call to InterfaceValue or a
-// call to FieldsOf.
+// arguments. Each argument is a function value, a provider set, a call to
+// Struct, a call to Bind, a call to Value, a call to InterfaceValue or a call
+// to FieldsOf.
 //
 // Passing a function value to NewSet declares that the function's first
 // return value type will be provided by calling the function. The arguments
@@ -44,15 +44,17 @@ type ProviderSet struct{}
 // will call all the appropriate cleanup functions and return the error from
 // the injector function.
 //
-// Passing a struct value of type S to NewSet declares that both S and *S will
-// be provided by creating a new value of the appropriate type by filling in
-// each field of S using the provider of the field's type.
-//
 // Passing a ProviderSet to NewSet is the same as if the set's contents
 // were passed as arguments to NewSet directly.
 //
 // The behavior of passing the result of a call to other functions in this
 // package are described in their respective doc comments.
+//
+// For compatibility with older versions of Wire, passing a struct value of type
+// S to NewSet declares that both S and *S will be provided by creating a new
+// value of the appropriate type by filling in each field of S using the
+// provider of the field's type. This form is deprecated and will be removed in
+// a future version of Wire: new providers sets should use wire.Struct.
 func NewSet(...interface{}) ProviderSet {
 	return ProviderSet{}
 }
@@ -137,6 +139,26 @@ func InterfaceValue(typ interface{}, x interface{}) ProvidedValue {
 	return ProvidedValue{}
 }
 
+// A StructProvider represents a named struct.
+type StructProvider struct{}
+
+// Struct specifies that the given struct type will be provided by filling in the fields
+// in the struct that have the names given. Each of the arguments must be a name
+// to the field they wish to reference. As a special case, if a single name "*"
+// is given, then all of the fields in the struct will be filled in.
+//
+// For example:
+//
+//  type S struct {
+//    MyFoo *Foo
+//    MyBar *Bar
+//  }
+//  var Set = wire.NewSet(wire.Struct(new(S), "MyFoo")) -> inject only S.MyFoo
+//  var Set = wire.NewSet(wire.Struct(new(S), "*")) -> inject all fields
+func Struct(structType interface{}, fieldNames ...string) StructProvider {
+	return StructProvider{}
+}
+
 // StructFields is a collection of the fields from a struct.
 type StructFields struct{}