New Mojom Parser: Serialization.

mojom/mojom_parser/serialization/serialization.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package serialization
 
 import (
+        "fmt"
+        "mojo/public/go/bindings"
+        "mojom/mojom_parser/generated/mojom_files"
+        "mojom/mojom_parser/generated/mojom_types"
         "mojom/mojom_parser/mojom"
 )
 
 //////////////////////////////////////////////////
 /// Mojom Descriptor Serialization
 //////////////////////////////////////////////////
 
+// This variable may be set to false in order to omit emitting line and
+// column numbers.
+var EmitLineAndColumnNumbers bool = true
+
 // Serializes the MojomDescriptor into a binary form that is passed to the
 // backend of the compiler in order to invoke the code generators.
 // To do this we use Mojo serialization.
 func Serialize(d *mojom.MojomDescriptor) (bytes []byte, err error) {
-        // TODO(rudominer) This is a stub. It will be implemented in a later
-        // CL.
-        bytes = []byte("DummyOutput")
+        fileGraph := translateDescriptor(d)
+        encoder := bindings.NewEncoder()
+        fileGraph.Encode(encoder)
+        bytes, _, err = encoder.Data()
         return
 }
+
+// translateDescriptor translates from a mojom.MojomDescriptor (the pure Go
+// representation used by the parser) to a mojom_files.MojomFileGraph (the
+// Mojo Go representation used for serialization.)
+func translateDescriptor(d *mojom.MojomDescriptor) *mojom_files.MojomFileGraph {
+        fileGraph := mojom_files.MojomFileGraph{}
+
+        // Add |files| field.
+        fileGraph.Files = make(map[string]mojom_files.MojomFile)
+        for name, file := range d.MojomFilesByName {
+                fileGraph.Files[name] = translateMojomFile(file)
+        }
+
+        // Add |resolved_types| field.
+        fileGraph.ResolvedTypes = make(map[string]mojom_types.UserDefinedType)
+        for key, userDefinedType := range d.TypesByKey {
+                fileGraph.ResolvedTypes[key] = translateUserDefinedType(userDefinedType)
+        }
+
+        // Add |resolved_values| field.
+        fileGraph.ResolvedValues = make(map[string]mojom_types.UserDefinedValue)
+        for key, userDefinedValue := range d.ValuesByKey {
+                fileGraph.ResolvedValues[key] = translateUserDefinedValue(userDefinedValue)
+        }
+
+        return &fileGraph
+}
+
+// translateMojomFile translates from a mojom.MojomFile (the pure Go
+// representation used by the parser) to a mojom_files.MojomFile (the
+// Mojo Go representation used for serialization.)
+func translateMojomFile(f *mojom.MojomFile) (file mojom_files.MojomFile) {
+        // file_name field
+        file.FileName = f.CanonicalFileName
+
+        // module_namespace field
+        file.ModuleNamespace = newString(f.ModuleNamespace)
+
+        // attributes field
+        if f.Attributes != nil {
+                file.Attributes = new([]mojom_types.Attribute)
+                for _, attr := range f.Attributes.List {
+                        *(file.Attributes) = append(*(file.Attributes), translateMojomAttribute(&attr))
+                }
+        }
+
+        // imports field
+        if len(f.Imports) > 0 {
+                file.Imports = new([]string)
+                for _, importName := range f.Imports {
+                        *(file.Imports) = append(*(file.Imports), importName.CanonicalFileName)
+                }
+        }
+
+        // declared_mojom_objects field...
+
+        // Interfaces
+        if f.Interfaces != nil && len(f.Interfaces) > 0 {
+                file.DeclaredMojomObjects.Interfaces = new([]string)
+                for _, intrfc := range f.Interfaces {
+                        *(file.DeclaredMojomObjects.Interfaces) = append(*(file.DeclaredMojomObjects.Interfaces), intrfc.TypeKey())
+                }
+        }
+
+        // Structs
+        if f.Structs != nil && len(f.Structs) > 0 {
+                file.DeclaredMojomObjects.Structs = new([]string)
+                for _, strct := range f.Structs {
+                        *(file.DeclaredMojomObjects.Structs) = append(*(file.DeclaredMojomObjects.Structs), strct.TypeKey())
+                }
+        }
+
+        // Unions
+        if f.Unions != nil && len(f.Unions) > 0 {
+                file.DeclaredMojomObjects.Unions = new([]string)
+                for _, union := range f.Unions {
+                        *(file.DeclaredMojomObjects.Unions) = append(*(file.DeclaredMojomObjects.Unions), union.TypeKey())
+                }
+        }
+
+        // TopLevelEnums
+        if f.Enums != nil && len(f.Enums) > 0 {
+                file.DeclaredMojomObjects.TopLevelEnums = new([]string)
+                for _, enum := range f.Enums {
+                        *(file.DeclaredMojomObjects.TopLevelEnums) = append(*(file.DeclaredMojomObjects.TopLevelEnums), enum.TypeKey())
+                }
+        }
+
+        // TopLevelConstants
+        if f.Constants != nil && len(f.Constants) > 0 {
+                file.DeclaredMojomObjects.TopLevelConstants = new([]string)
+                for _, constant := range f.Constants {
+                        *(file.DeclaredMojomObjects.TopLevelConstants) = append(*(file.DeclaredMojomObjects.TopLevelConstants), constant.ValueKey())
+                }
+        }
+
+        // TODO(rudominer) Do we need the EmbeddedEnums and EmbeddedConstants
+        // fields in KeysByType. It seems these fields are not currently being
+        // used in mojom_translator.py.
+
+        return
+}
+
+// translateUserDefinedType translates from a mojom.UserDefinedType (the pure Go
+// representation used by the parser) to a mojom_types.UserDefinedType (the
+// Mojo Go representation used for serialization.)
+func translateUserDefinedType(t mojom.UserDefinedType) mojom_types.UserDefinedType {
+        switch p := t.(type) {
+        case *mojom.MojomStruct:
+                return &mojom_types.UserDefinedTypeStructType{translateMojomStruct(p)}
+        case *mojom.MojomInterface:
+                return translateMojomInterface(p)
+        case *mojom.MojomEnum:
+                return translateMojomEnum(p)
+        case *mojom.MojomUnion:
+                return translateMojomUnion(p)
+        default:
+                panic(fmt.Sprintf("Unexpected type: %T", t))
+
+        }
+}
+
+func translateMojomStruct(s *mojom.MojomStruct) mojom_types.MojomStruct {
+        mojomStruct := mojom_types.MojomStruct{}
+        mojomStruct.DeclData = translateDeclarationData(&s.DeclarationData)
+        mojomStruct.DeclData.ContainedDeclarations = translateContainedDeclarations(&s.DeclarationContainer)
+
+        for _, field := range s.Fields {
+                mojomStruct.Fields = append(mojomStruct.Fields, translateStructField(field))
+        }
+
+        // TODO(rudominer) Implement VersionInfo.
+        //mojomStruct.Value.VersionInfo = new([]mojom_types.StructVersion)
+
+        return mojomStruct
+}
+
+func translateStructField(f *mojom.StructField) (field mojom_types.StructField) {
+        field.DeclData = translateDeclarationData(&f.DeclarationData)
+        field.Type = translateTypeRef(f.FieldType)
+        if f.DefaultValue != nil {
+                field.DefaultValue = translateDefaultFieldValue(f.DefaultValue)
+        }
+        // TODO(rudominer) Implement field offsets.
+        field.Offset = f.Offset
+        return
+}
+
+func translateDefaultFieldValue(v mojom.ValueRef) mojom_types.DefaultFieldValue {
+        switch v := v.(type) {
+        case mojom.LiteralValue:
+                if v.IsDefault() {
+                        return &mojom_types.DefaultFieldValueDefaultKeyword{mojom_types.DefaultKeyword{}}
+                }
+                return &mojom_types.DefaultFieldValueValue{translateLiteralValue(v)}
+        case *mojom.UserValueRef:
+                switch t := v.ResolvedConcreteValue().(type) {
+                case mojom.BuiltInConstantValue:
+                        return &mojom_types.DefaultFieldValueValue{translateBuiltInConstantValue(t)}
+                default:
+                        return &mojom_types.DefaultFieldValueValue{translateUserValueRef(v)}
+                }
+        default:
+                panic(fmt.Sprintf("Unexpected ValueRef type: %T", v))
+
+        }
+}
+
+func translateMojomInterface(intrfc *mojom.MojomInterface) *mojom_types.UserDefinedTypeInterfaceType {
+        mojomInterface := mojom_types.UserDefinedTypeInterfaceType{}
+
+        mojomInterface.Value.DeclData = translateDeclarationData(&intrfc.DeclarationData)
+        mojomInterface.Value.DeclData.ContainedDeclarations = translateContainedDeclarations(&intrfc.DeclarationContainer)
+
+        // TODO(rudominer) The Interface name field need not be the name from the .mojom file.
+        mojomInterface.Value.InterfaceName = intrfc.SimpleName()
+
+        mojomInterface.Value.Methods = make(map[uint32]mojom_types.MojomMethod)
+        for ordinal, method := range intrfc.MethodsByOrdinal {
+                mojomInterface.Value.Methods[ordinal] = translateMojomMethod(method)
+        }
+
+        return &mojomInterface
+}
+
+func translateMojomMethod(method *mojom.MojomMethod) mojom_types.MojomMethod {
+        mojomMethod := mojom_types.MojomMethod{}
+
+        // decl_data
+        mojomMethod.DeclData = translateDeclarationData(&method.DeclarationData)
+
+        // parameters
+        mojomMethod.Parameters = translateMojomStruct(method.Parameters)
+
+        // response_params
+        if method.ResponseParameters != nil {
+                responseParams := translateMojomStruct(method.ResponseParameters)
+                mojomMethod.ResponseParams = &responseParams
+        }
+
+        // ordinal
+        mojomMethod.Ordinal = method.Ordinal
+        return mojomMethod
+}
+
+func translateMojomEnum(enum *mojom.MojomEnum) *mojom_types.UserDefinedTypeEnumType {
+        mojomEnum := mojom_types.UserDefinedTypeEnumType{}
+        mojomEnum.Value.DeclData = translateDeclarationData(&enum.DeclarationData)
+        for _, value := range enum.Values {
+                mojomEnum.Value.Values = append(mojomEnum.Value.Values, translateEnumValue(value))
+        }
+        return &mojomEnum
+}
+
+func translateMojomUnion(union *mojom.MojomUnion) *mojom_types.UserDefinedTypeUnionType {
+        mojomUnion := mojom_types.UserDefinedTypeUnionType{}
+        mojomUnion.Value.DeclData = translateDeclarationData(&union.DeclarationData)
+        for _, field := range union.Fields {
+                mojomUnion.Value.Fields = append(mojomUnion.Value.Fields,
+                        translateUnionField(field))
+        }
+        return &mojomUnion
+}
+
+func translateUnionField(unionField mojom.UnionField) mojom_types.UnionField {
+        outUnionField := mojom_types.UnionField{}
+        outUnionField.DeclData = translateDeclarationData(&unionField.DeclarationData)
+        outUnionField.Type = translateTypeRef(unionField.FieldType)
+        outUnionField.Tag = unionField.Tag
+        return outUnionField
+}
+
+// WARNING: Do not invoke this function on a UserDefinedValue of type BuiltInConstantValue because
+// objects of those types do not have a type_key and do not correspond to a mojom_types.UserDefinedValue.
+func translateUserDefinedValue(v mojom.UserDefinedValue) mojom_types.UserDefinedValue {
+        switch t := v.(type) {
+        case *mojom.UserDefinedConstant:
+                return translateUserDefinedConstant(t)
+        case *mojom.EnumValue:
+                return &mojom_types.UserDefinedValueEnumValue{translateEnumValue(t)}
+        case *mojom.BuiltInConstantValue:
+                panic("Do not invoke translateUserDefinedValue on BuiltInConstantValue.")
+        default:
+                panic(fmt.Sprintf("Unexpected UserDefinedValue type %T", v))
+
+        }
+}
+
+func translateUserDefinedConstant(t *mojom.UserDefinedConstant) *mojom_types.UserDefinedValueDeclaredConstant {
+        declaredConstant := mojom_types.UserDefinedValueDeclaredConstant{}
+        declaredConstant.Value.Type = translateTypeRef(t.DeclaredType())
+        declaredConstant.Value.DeclData = *translateDeclarationData(&t.DeclarationData)
+        declaredConstant.Value.Value = translateValueRef(t.ValueRef())
+        return &declaredConstant
+}
+
+func translateEnumValue(v *mojom.EnumValue) mojom_types.EnumValue {
+        enumValue := mojom_types.EnumValue{}
+        enumValue.DeclData = translateDeclarationData(&v.DeclarationData)
+        enumValue.EnumTypeKey = v.EnumType().TypeKey()
+        if v.ValueRef() != nil {
+                enumValue.InitializerValue = translateValueRef(v.ValueRef())
+        }
+        // TODO(rudominer) enumValue.IntValue should be set to v.ComputedIntValue
+        // once MojomDescriptor.ComputeEnumValueIntegers() is implemented.
+        enumValue.IntValue = v.Int32Value()
+        return enumValue
+}
+
+func translateTypeRef(typeRef mojom.TypeRef) mojom_types.Type {
+        switch t := typeRef.(type) {
+        case mojom.SimpleType:
+                return translateSimpleType(t)
+        case mojom.StringType:
+                return translateStringType(t)
+        case mojom.HandleTypeRef:
+                return translateHandleType(t)
+        case mojom.ArrayTypeRef:
+                return translateArrayType(t)
+        case mojom.MapTypeRef:
+                return translateMapType(t)
+        case *mojom.UserTypeRef:
+                return translateUserTypeRef(t)
+        default:
+                panic(fmt.Sprintf("Unexpected TypeRef type %T", t))
+        }
+}
+
+func translateSimpleType(simpleType mojom.SimpleType) *mojom_types.TypeSimpleType {
+        var value mojom_types.SimpleType
+        switch simpleType {
+        case mojom.SimpleTypeBool:
+                value = mojom_types.SimpleType_Bool
+        case mojom.SimpleTypeDouble:
+                value = mojom_types.SimpleType_Double
+        case mojom.SimpleTypeFloat:
+                value = mojom_types.SimpleType_Float
+        case mojom.SimpleTypeInt8:
+                value = mojom_types.SimpleType_InT8
+        case mojom.SimpleTypeInt16:
+                value = mojom_types.SimpleType_InT16
+        case mojom.SimpleTypeInt32:
+                value = mojom_types.SimpleType_InT32
+        case mojom.SimpleTypeInt64:
+                value = mojom_types.SimpleType_InT64
+        case mojom.SimpleTypeUInt8:
+                value = mojom_types.SimpleType_UinT8
+        case mojom.SimpleTypeUInt16:
+                value = mojom_types.SimpleType_UinT16
+        case mojom.SimpleTypeUInt32:
+                value = mojom_types.SimpleType_UinT32
+        case mojom.SimpleTypeUInt64:
+                value = mojom_types.SimpleType_UinT64
+        }
+        return &mojom_types.TypeSimpleType{value}
+}
+
+func translateStringType(stringType mojom.StringType) *mojom_types.TypeStringType {
+        return &mojom_types.TypeStringType{mojom_types.StringType{stringType.Nullable()}}
+}
+
+func translateHandleType(handleType mojom.HandleTypeRef) *mojom_types.TypeHandleType {
+        var kind mojom_types.HandleType_Kind
+        switch handleType.HandleKind() {
+        case mojom.HandleKindUnspecified:
+                kind = mojom_types.HandleType_Kind_Unspecified
+        case mojom.HandleKindMessagePipe:
+                kind = mojom_types.HandleType_Kind_MessagePipe
+        case mojom.HandleKindDataPipeConsumer:
+                kind = mojom_types.HandleType_Kind_DataPipeConsumer
+        case mojom.HandleKindDataPipeProducer:
+                kind = mojom_types.HandleType_Kind_DataPipeProducer
+        case mojom.HandleKindSharedBuffer:
+                kind = mojom_types.HandleType_Kind_SharedBuffer
+        }
+        return &mojom_types.TypeHandleType{mojom_types.HandleType{handleType.Nullable(), kind}}
+}
+
+func translateArrayType(arrayType mojom.ArrayTypeRef) *mojom_types.TypeArrayType {
+        return &mojom_types.TypeArrayType{mojom_types.ArrayType{
+                Nullable:    arrayType.Nullable(),
+                FixedLength: int32(arrayType.FixedLength()),
+                ElementType: translateTypeRef(arrayType.ElementType())}}
+}
+
+func translateMapType(mapType mojom.MapTypeRef) *mojom_types.TypeMapType {
+        return &mojom_types.TypeMapType{mojom_types.MapType{
+                Nullable:  mapType.Nullable(),
+                KeyType:   translateTypeRef(mapType.KeyType()),
+                ValueType: translateTypeRef(mapType.ValueType())}}
+}
+
+func translateUserTypeRef(userType *mojom.UserTypeRef) *mojom_types.TypeTypeReference {
+        typeKey := newString(userType.ResolvedType().TypeKey())
+        identifier := newString(userType.Identifier())
+        return &mojom_types.TypeTypeReference{mojom_types.TypeReference{
+                Nullable:           userType.Nullable(),
+                IsInterfaceRequest: userType.IsInterfaceRequest(),
+                Identifier:         identifier,
+                TypeKey:            typeKey}}
+}
+
+func translateValueRef(valueRef mojom.ValueRef) mojom_types.Value {
+        switch valueRef := valueRef.(type) {
+        case mojom.LiteralValue:
+                return translateLiteralValue(valueRef)
+        case *mojom.UserValueRef:
+                return translateUserValueRef(valueRef)
+        default:
+                panic(fmt.Sprintf("Unexpected ValueRef type %T", valueRef))
+        }
+}
+
+func translateLiteralValue(v mojom.LiteralValue) *mojom_types.ValueLiteralValue {
+        var lv mojom_types.LiteralValue
+        switch v.ValueType() {
+        case mojom.SimpleTypeBool:
+                lv = &mojom_types.LiteralValueBoolValue{v.Value().(bool)}
+        case mojom.SimpleTypeDouble:
+                lv = &mojom_types.LiteralValueDoubleValue{v.Value().(float64)}
+        case mojom.SimpleTypeFloat:
+                lv = &mojom_types.LiteralValueFloatValue{v.Value().(float32)}
+        case mojom.SimpleTypeInt8:
+                lv = &mojom_types.LiteralValueInt8Value{v.Value().(int8)}
+        case mojom.SimpleTypeInt16:
+                lv = &mojom_types.LiteralValueInt16Value{v.Value().(int16)}
+        case mojom.SimpleTypeInt32:
+                lv = &mojom_types.LiteralValueInt32Value{v.Value().(int32)}
+        case mojom.SimpleTypeInt64:
+                lv = &mojom_types.LiteralValueInt64Value{v.Value().(int64)}
+        case mojom.SimpleTypeUInt8:
+                lv = &mojom_types.LiteralValueUint8Value{v.Value().(uint8)}
+        case mojom.SimpleTypeUInt16:
+                lv = &mojom_types.LiteralValueUint16Value{v.Value().(uint16)}
+        case mojom.SimpleTypeUInt32:
+                lv = &mojom_types.LiteralValueUint32Value{v.Value().(uint32)}
+        case mojom.SimpleTypeUInt64:
+                lv = &mojom_types.LiteralValueUint64Value{v.Value().(uint64)}
+        case mojom.StringLiteralType:
+                lv = &mojom_types.LiteralValueStringValue{v.Value().(string)}
+        default:
+                panic(fmt.Sprintf("Unexpected literal value type %d", v.ValueType()))
+        }
+        return &mojom_types.ValueLiteralValue{lv}
+}
+
+func translateBuiltInConstantValue(t mojom.BuiltInConstantValue) *mojom_types.ValueBuiltinValue {
+        builtInValue := mojom_types.ValueBuiltinValue{}
+        switch t {
+        case mojom.SimpleTypeFloat_INFINITY:
+                builtInValue.Value = mojom_types.BuiltinConstantValue_FloatInfinity
+        case mojom.SimpleTypeFloat_NEGATIVE_INFINITY:
+                builtInValue.Value = mojom_types.BuiltinConstantValue_FloatNegativeInfinity
+        case mojom.SimpleTypeFloat_NAN:
+                builtInValue.Value = mojom_types.BuiltinConstantValue_FloatNan
+        case mojom.SimpleTypeDouble_INFINITY:
+                builtInValue.Value = mojom_types.BuiltinConstantValue_DoubleInfinity
+        case mojom.SimpleTypeDouble_NEGATIVE_INFINITY:
+                builtInValue.Value = mojom_types.BuiltinConstantValue_DoubleNegativeInfinity
+        case mojom.SimpleTypeDouble_NAN:
+                builtInValue.Value = mojom_types.BuiltinConstantValue_DoubleNegativeInfinity
+        default:
+                panic(fmt.Sprintf("Unrecognized BuiltInConstantValue %v", t))
+        }
+        return &builtInValue
+}
+
+func translateUserValueRef(r *mojom.UserValueRef) *mojom_types.ValueUserValueReference {
+        valueKey := newString(r.ResolvedDeclaredValue().ValueKey())
+        return &mojom_types.ValueUserValueReference{mojom_types.UserValueReference{
+                Identifier:            r.Identifier(),
+                ValueKey:              valueKey,
+                ResolvedConcreteValue: translateConcreteValue(r.ResolvedConcreteValue())}}
+}
+
+func translateConcreteValue(v mojom.ConcreteValue) mojom_types.Value {
+        switch t := v.(type) {
+        case mojom.BuiltInConstantValue:
+                return translateBuiltInConstantValue(t)
+        case mojom.LiteralValue:
+                return translateLiteralValue(t)
+        case *mojom.EnumValue:
+                // Note that in the pure Go representation we support the abstraction
+                // that an EnumValue is a type of ConcreteValue. This makes sense because
+                // an Enum is abstractly a finite set of values that need not have
+                // a corresponding integer value. However in mojom_types.mojom we currently
+                // do not support this abstraction: the only concrete values are the literal
+                // values and the BuiltInConstantValues. Consequently here we return the
+                // Int32Value() of the EnumValue.
+                return &mojom_types.ValueLiteralValue{&mojom_types.LiteralValueInt32Value{t.Int32Value()}}
+        default:
+                panic(fmt.Sprintf("Unexpected type %T", v))
+        }
+}
+
+func translateDeclarationData(d *mojom.DeclarationData) *mojom_types.DeclarationData {
+        declData := mojom_types.DeclarationData{}
+
+        // attributes field
+        if d.Attributes() != nil {
+                declData.Attributes = new([]mojom_types.Attribute)
+                for _, attr := range d.Attributes().List {
+                        *(declData.Attributes) = append(*(declData.Attributes), translateMojomAttribute(&attr))
+                }
+        }
+
+        // min_version field
+        // TODO(rudominer) Eliminate the min_version field from struct DeclarationData
+
+        // short_name field
+        declData.ShortName = newString(d.SimpleName())
+
+        // full_identifier field
+        declData.FullIdentifier = newString(d.FullyQualifiedName())
+
+        // declared_ordinal field
+        if d.DeclaredOrdinal() < 0 {
+                declData.DeclaredOrdinal = -1
+        } else {
+                declData.DeclaredOrdinal = int32(d.DeclaredOrdinal())
+        }
+
+        // declaration_order
+        // TODO(rudominer) DeclarationOrder is currently not populated.
+        declData.DeclarationOrder = -1
+
+        // source_file_info
+        declData.SourceFileInfo = new(mojom_types.SourceFileInfo)
+        declData.SourceFileInfo.FileName = d.OwningFile().CanonicalFileName
+        if EmitLineAndColumnNumbers {
+                declData.SourceFileInfo.LineNumber = d.LineNumber()
+                declData.SourceFileInfo.ColumnNumber = d.ColumnNumber()
+        }
+        return &declData
+}
+
+// Returns nil if there are no contained declarations
+func translateContainedDeclarations(container *mojom.DeclarationContainer) *mojom_types.ContainedDeclarations {
+        if container.Enums == nil && container.Constants == nil {
+                return nil
+        }
+        declarations := mojom_types.ContainedDeclarations{}
+        if container.Enums != nil {
+                declarations.Enums = new([]string)
+                for _, enum := range container.Enums {
+                        *declarations.Enums = append(*declarations.Enums, enum.TypeKey())
+                }
+        }
+        if container.Constants != nil {
+                declarations.Constants = new([]string)
+                for _, constant := range container.Constants {
+                        *declarations.Constants = append(*declarations.Constants, constant.ValueKey())
+                }
+        }
+        return &declarations
+}
+
+func translateMojomAttribute(a *mojom.MojomAttribute) (attribute mojom_types.Attribute) {
+        // TODO(rudominer) Improve representation of attribute values.
+        return mojom_types.Attribute{a.Key, fmt.Sprintf("%v", a.Value.Value())}
+}
+
+// newString is a convenience function for creating a pointer to a string whose value
+// is the specified string. It is necessary to create pointers to strings because
+// that is how the Mojom type string? (i.e. nullable string) is represented in
+// in the Mojom Go bindings.
+func newString(s string) *string {
+        t := new(string)
+        *t = s
+        return t
+}