lib/vdl/codegen/javascript/gen.go - release.go.x.ref - Git at Google

 // Copyright 2015 The Vanadium 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 javascript implements Javascript code generation from compiled VDL packages.
 package javascript

 // Generates the javascript source code for vdl files.  The generated output in javascript
 // differs from most other languages, since we don't generate stubs. Instead generate an
 // object that contains the parsed VDL structures that will be used by the Javascript code
 // to valid servers.

 import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
 	"path/filepath"
 	"strconv"
 	"strings"
 	"text/template"

 	"v.io/v23/vdl"
 	"v.io/x/ref/lib/vdl/compile"
 	"v.io/x/ref/lib/vdl/vdlutil"
 )

 type data struct {
 	Pkg            *compile.Package
 	Env            *compile.Env
 	GenerateImport func(string) string
 	UserImports    jsImports
 	PathToCoreJS   string
 	TypeNames      typeNames
 }

 // Generate takes a populated compile.Package and produces a byte slice
 // containing the generated Javascript code.
 func Generate(pkg *compile.Package, env *compile.Env, genImport func(string) string, pathToCoreJS string) []byte {
 	data := data{
 		Pkg:            pkg,
 		Env:            env,
 		GenerateImport: genImport,
 		UserImports:    jsImportsForFiles(pkg.Files...),
 		TypeNames:      newTypeNames(pkg),
 		PathToCoreJS:   pathToCoreJS,
 	}
 	var buf bytes.Buffer
 	if err := javascriptTemplate.Execute(&buf, data); err != nil {
 		// We shouldn't see an error; it means our template is buggy.
 		panic(fmt.Errorf("vdl: couldn't execute template: %v", err))
 	}
 	return buf.Bytes()
 }

 var javascriptTemplate *template.Template

 func bitlen(kind vdl.Kind) int {
 	switch kind {
 	case vdl.Float32, vdl.Complex64:
 		return 32
 	case vdl.Float64, vdl.Complex128:
 		return 64
 	}
 	panic(fmt.Errorf("vdl: bitLen unhandled kind %v", kind))
 }

 func genMethodTags(names typeNames, method *compile.Method) string {
 	tags := method.Tags
 	result := "["
 	for _, tag := range tags {
 		result += typedConst(names, tag) + ", "
 	}
 	result += "]"
 	return result
 }

 // Format the given int64 into a JS BigInt.
 func formatUint64BigInt(v uint64) string {
 	buffer := make([]byte, 8)
 	binary.BigEndian.PutUint64(buffer, v)
 	sign := "0"
 	if v > 0 {
 		sign = "1"
 	}
 	return fmt.Sprintf("new vdl.BigInt(%s, %s)", sign, formatByteBuffer(buffer))
 }

 // Format the given int64 into a JS BigInt.
 func formatInt64BigInt(v int64) string {
 	buffer := make([]byte, 8)
 	var sign int64 = 0
 	if v > 0 {
 		sign = 1
 	} else if v < 0 {
 		sign = -1
 	}
 	binary.BigEndian.PutUint64(buffer, uint64(v*sign)) // Adjust value by sign.

 	return fmt.Sprintf("new vdl.BigInt(%d, %s)", sign, formatByteBuffer(buffer))
 }

 // Given a buffer of bytes, create the JS Uint8Array that corresponds to it (to be used with BigInt).
 func formatByteBuffer(buffer []byte) string {
 	buf := bytes.TrimLeft(buffer, "\x00") // trim leading zeros
 	str := "new Uint8Array(["
 	for i, b := range buf {
 		if i > 0 {
 			str += ", "
 		}
 		str += fmt.Sprintf("%#x", b)
 	}
 	str += "])"
 	return str
 }

 // untypedConst generates a javascript string representing a constant that is
 // not wrapped with type information.
 func untypedConst(names typeNames, v *vdl.Value) string {
 	switch v.Kind() {
 	case vdl.Bool:
 		if v.Bool() {
 			return "true"
 		} else {
 			return "false"
 		}
 	case vdl.Byte:
 		return strconv.FormatUint(uint64(v.Byte()), 10)
 	case vdl.Uint16, vdl.Uint32:
 		return strconv.FormatUint(v.Uint(), 10)
 	case vdl.Int16, vdl.Int32:
 		return strconv.FormatInt(v.Int(), 10)
 	case vdl.Uint64:
 		return formatUint64BigInt(v.Uint())
 	case vdl.Int64:
 		return formatInt64BigInt(v.Int())
 	case vdl.Float32, vdl.Float64:
 		return strconv.FormatFloat(v.Float(), 'g', -1, bitlen(v.Kind()))
 	case vdl.String:
 		return strconv.Quote(v.RawString())
 	case vdl.Any:
 		if v.Elem() != nil {
 			return typedConst(names, v.Elem())
 		}
 		return "null"
 	case vdl.Optional:
 		if v.Elem() != nil {
 			return untypedConst(names, v.Elem())
 		}
 		return "null"
 	case vdl.Complex64, vdl.Complex128:
 		return fmt.Sprintf("new vdl.Complex(%f, %f)", real(v.Complex()), imag(v.Complex()))
 	case vdl.Enum:
 		return fmt.Sprintf("'%s'", v.EnumLabel())
 	case vdl.Array, vdl.List:
 		result := "["
 		for ix := 0; ix < v.Len(); ix++ {
 			val := untypedConst(names, v.Index(ix))
 			result += "\n" + val + ","
 		}
 		result += "\n]"
 		if v.Type().Elem().Kind() == vdl.Byte {
 			return "new Uint8Array(" + result + ")"
 		}
 		return result
 	case vdl.Set:
 		result := "new Set(["
 		for _, key := range vdl.SortValuesAsString(v.Keys()) {
 			result += "\n  " + untypedConst(names, key) + ", "
 		}
 		result += "])"
 		return result
 	case vdl.Map:
 		result := "new Map(["
 		for i, key := range vdl.SortValuesAsString(v.Keys()) {
 			if i > 0 {
 				result += ","
 			}
 			result += fmt.Sprintf("\n  [%s, %s]",
 				untypedConst(names, key),
 				untypedConst(names, v.MapIndex(key)))

 		}
 		result += "])"
 		return result
 	case vdl.Struct:
 		result := "{"
 		t := v.Type()
 		for ix := 0; ix < t.NumField(); ix++ {
 			result += "\n  '" +
 				vdlutil.FirstRuneToLower(t.Field(ix).Name) +
 				"': " +
 				untypedConst(names, v.StructField(ix)) +
 				","
 		}
 		return result + "\n}"
 	case vdl.Union:
 		ix, innerVal := v.UnionField()
 		return fmt.Sprintf("{ %q: %v }", vdlutil.FirstRuneToLower(v.Type().Field(ix).Name), untypedConst(names, innerVal))
 	case vdl.TypeObject:
 		return names.LookupType(v.TypeObject())
 	default:
 		panic(fmt.Errorf("vdl: untypedConst unhandled type %v %v", v.Kind(), v.Type()))
 	}
 }

 // typedConst returns a javascript string representing a const that is always
 // wrapped with type information
 func typedConst(names typeNames, v *vdl.Value) string {
 	if v.Kind() == vdl.TypeObject || v.Kind() == vdl.Any {
 		return untypedConst(names, v)
 	}
 	if v.Kind() == vdl.Enum && names.IsDefinedInExternalPkg(v.Type()) {
 		return fmt.Sprintf("%s.%s", qualifiedName(v.Type()), vdlutil.ToConstCase(v.EnumLabel()))
 	}
 	// We call canonicalize.reduce so that we convert to native types
 	// The constructor would have done the reduction of the field values
 	// but it doesn't convert to native types.
 	return fmt.Sprintf("canonicalize.reduce(new %s(%s, true), %s)",
 		names.LookupConstructor(v.Type()),
 		untypedConst(names, v),
 		names.LookupType(v.Type()))
 }

 // Returns a Not Implemented stub for the method
 func generateMethodStub(method *compile.Method) string {
 	args := "ctx, serverCall"
 	for _, arg := range method.InArgs {
 		args += fmt.Sprintf(", %s", arg.Name)
 	}

 	return fmt.Sprintf(`function(%s) {
   throw new Error('Method %s not implemented');
 }`, args, method.Name)
 }

 // Returns the JS version of the method signature.
 func generateMethodSignature(method *compile.Method, names typeNames) string {
 	return fmt.Sprintf(`{
     name: '%s',
     doc: %s,
     inArgs: %s,
     outArgs: %s,
     inStream: %s,
     outStream: %s,
     tags: %s
   }`,
 		method.Name,
 		quoteStripDoc(method.Doc),
 		generateMethodArguments(method.InArgs, names),
 		generateMethodArguments(method.OutArgs, names),
 		generateMethodStreaming(method.InStream, names),
 		generateMethodStreaming(method.OutStream, names),
 		genMethodTags(names, method))
 }

 // Returns a slice describing the method's arguments.
 func generateMethodArguments(args []*compile.Field, names typeNames) string {
 	ret := "["
 	for _, arg := range args {
 		ret += fmt.Sprintf(
 			`{
       name: '%s',
       doc: %s,
       type: %s
     },
     `, arg.Name, quoteStripDoc(arg.Doc), names.LookupType(arg.Type))
 	}
 	ret += "]"
 	return ret
 }

 // Returns the VOM type of the stream.
 func generateMethodStreaming(streaming *vdl.Type, names typeNames) string {
 	if streaming == nil {
 		return "null"
 	}
 	return fmt.Sprintf(
 		`{
       name: '',
       doc: '',
       type: %s
     }`,
 		names.LookupType(streaming))
 }

 // Returns a slice of embeddings with the proper qualified identifiers.
 func generateEmbeds(embeds []*compile.Interface) string {
 	result := "["
 	for _, embed := range embeds {
 		result += fmt.Sprintf(`{
       name: '%s',
       pkgPath: '%s',
       doc: %s
     },
     `, embed.Name, embed.File.Package.Path, quoteStripDoc(embed.Doc))
 	}
 	result += "]"
 	return result
 }

 func importPath(data data, path string) string {
 	// We need to prefix all of these paths with a ./ to tell node that the path is relative to
 	// the current directory.  Sadly filepath.Join(".", foo) == foo, so we have to do it
 	// explicitly.
 	return "." + string(filepath.Separator) + data.GenerateImport(path)
 }

 func quoteStripDoc(doc string) string {
 	// TODO(alexfandrianto): We need to handle '// ' and '\n' in the docstring.
 	// It would also be nice to single-quote the whole string.
 	trimmed := strings.Trim(doc, "\n")
 	return strconv.Quote(trimmed)
 }

 func hasErrors(pkg *compile.Package) bool {
 	for _, file := range pkg.Files {
 		if len(file.ErrorDefs) > 0 {
 			return true
 		}
 	}
 	return false
 }

 func hasConsts(pkg *compile.Package) bool {
 	for _, file := range pkg.Files {
 		if len(file.ConstDefs) > 0 {
 			return true
 		}
 	}
 	return false
 }

 func hasEnums(pkg *compile.Package) bool {
 	for _, file := range pkg.Files {
 		for _, def := range file.TypeDefs {
 			if def.Type.Kind() == vdl.Enum {
 				return true
 			}
 		}
 	}
 	return false
 }

 func hasMethodTags(pkg *compile.Package) bool {
 	for _, file := range pkg.Files {
 		for _, iface := range file.Interfaces {
 			for _, method := range iface.Methods {
 				if len(method.Tags) > 0 {
 					return true
 				}
 			}
 		}
 	}
 	return false
 }

 func generateSystemImports(data data) string {
 	res := "var vdl = require('"
 	packagePrefix := ""
 	if data.PathToCoreJS != "" {
 		packagePrefix = strings.Repeat("../", strings.Count(data.Pkg.Path, "/")+1) + data.PathToCoreJS
 	}
 	if data.PathToCoreJS != "" {
 		res += packagePrefix + "/vdl');"
 	} else {
 		res += "vanadium').vdl;"
 	}
 	res += "\n"
 	if hasErrors(data.Pkg) {
 		if data.PathToCoreJS != "" {
 			res += "var makeError = require('" + packagePrefix + "/verror/make-errors');\n"
 			res += "var actions = require('" + packagePrefix + "/verror/actions');\n"
 		} else {
 			res += "var makeError = require('vanadium').verror.makeError;\n"
 			res += "var actions = require('vanadium').verror.actions;\n"
 		}
 	}

 	if hasConsts(data.Pkg) || hasEnums(data.Pkg) || hasMethodTags(data.Pkg) {
 		if data.PathToCoreJS != "" {
 			res += "var canonicalize = require('" + packagePrefix + "/vdl/canonicalize');\n"
 		} else {
 			res += "var canonicalize = require('vanadium').vdl.canonicalize;\n"
 		}
 	}
 	return res
 }

 func init() {
 	funcMap := template.FuncMap{
 		"firstRuneToLower":          vdlutil.FirstRuneToLower,
 		"genMethodTags":             genMethodTags,
 		"makeTypeDefinitionsString": makeTypeDefinitionsString,
 		"typedConst":                typedConst,
 		"generateEmbeds":            generateEmbeds,
 		"generateMethodStub":        generateMethodStub,
 		"generateMethodSignature":   generateMethodSignature,
 		"importPath":                importPath,
 		"quoteStripDoc":             quoteStripDoc,
 		"generateErrorConstructor":  generateErrorConstructor,
 		"generateSystemImports":     generateSystemImports,
 	}
 	javascriptTemplate = template.Must(template.New("genJS").Funcs(funcMap).Parse(genJS))
 }

 // The template that we execute against a compile.Package instance to generate our
 // code.  Most of this is fairly straightforward substitution and ranges; more
 // complicated logic is delegated to the helper functions above.
 //
 // We try to generate code that has somewhat reasonable formatting.
 const genJS = `{{with $data := .}}{{$data.Pkg.FileDoc}}
 // This file was auto-generated by the vanadium vdl tool.
 {{generateSystemImports $data}}

 {{/* Define additional imported modules. */}}
 {{$pkg := $data.Pkg}}
 {{if $data.UserImports}}{{range $imp := $data.UserImports}}
 var {{$imp.Local}} = require('{{importPath $data $imp.Path}}');{{end}}{{end}}

 module.exports = {};


 {{/* Define any types introduced by the VDL file. */}}
 // Types:
 {{makeTypeDefinitionsString $data.TypeNames }}


 {{/* Define all constants as typed constants. */}}
 // Consts:
 {{range $file := $pkg.Files}}{{range $const := $file.ConstDefs}}
   module.exports.{{$const.Name}} = {{typedConst $data.TypeNames $const.Value}};
 {{end}}{{end}}

 {{/* Define all errors. */}}
 // Errors:
 {{range $file := $pkg.Files}}{{range $error := $file.ErrorDefs}}
 {{generateErrorConstructor $data.TypeNames $error}}
 {{end}}{{end}}

 {{/* Define each of those service interfaces here, including method stubs and
      service signature. */}}
 // Services:
 {{range $file := $pkg.Files}}
   {{range $iface := $file.Interfaces}}
     {{/* Define the service interface. */}}
 function {{$iface.Name}}(){}
 module.exports.{{$iface.Name}} = {{$iface.Name}};

     {{range $method := $iface.AllMethods}}
       {{/* Add each method to the service prototype. */}}
 {{$iface.Name}}.prototype.{{firstRuneToLower $method.Name}} = {{generateMethodStub $method}};
     {{end}} {{/* end range $iface.AllMethods */}}

     {{/* The service signature encodes the same info as signature.Interface.
          TODO(alexfandrianto): We want to associate the signature type here, but
          it's complicated.
          For now, we need to pass the type in manually into encode. */}}
 {{$iface.Name}}.prototype._serviceDescription = {
   name: '{{$iface.Name}}',
   pkgPath: '{{$pkg.Path}}',
   doc: {{quoteStripDoc $iface.Doc}},
   embeds: {{generateEmbeds $iface.Embeds}},
   methods: [
     {{range $method := $iface.AllMethods}}
       {{/* Each method signature contains the information in rpc.MethodSig. */}}
     {{generateMethodSignature $method $data.TypeNames}},
     {{end}} {{/*end range $iface.AllMethods*/}}
   ]
 };

   {{end}} {{/* end range $files.Interfaces */}}
 {{end}} {{/* end range $pkg.Files */}}


 {{end}}`
	// Copyright 2015 The Vanadium 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 javascript implements Javascript code generation from compiled VDL packages.
	package javascript

	// Generates the javascript source code for vdl files. The generated output in javascript
	// differs from most other languages, since we don't generate stubs. Instead generate an
	// object that contains the parsed VDL structures that will be used by the Javascript code
	// to valid servers.

	import (
	"bytes"
	"encoding/binary"
	"fmt"
	"path/filepath"
	"strconv"
	"strings"
	"text/template"

	"v.io/v23/vdl"
	"v.io/x/ref/lib/vdl/compile"
	"v.io/x/ref/lib/vdl/vdlutil"
	)

	type data struct {
	Pkg *compile.Package
	Env *compile.Env
	GenerateImport func(string) string
	UserImports jsImports
	PathToCoreJS string
	TypeNames typeNames
	}

	// Generate takes a populated compile.Package and produces a byte slice
	// containing the generated Javascript code.
	func Generate(pkg compile.Package, env compile.Env, genImport func(string) string, pathToCoreJS string) []byte {
	data := data{
	Pkg: pkg,
	Env: env,
	GenerateImport: genImport,
	UserImports: jsImportsForFiles(pkg.Files...),
	TypeNames: newTypeNames(pkg),
	PathToCoreJS: pathToCoreJS,
	}
	var buf bytes.Buffer
	if err := javascriptTemplate.Execute(&buf, data); err != nil {
	// We shouldn't see an error; it means our template is buggy.
	panic(fmt.Errorf("vdl: couldn't execute template: %v", err))
	}
	return buf.Bytes()
	}

	var javascriptTemplate *template.Template

	func bitlen(kind vdl.Kind) int {
	switch kind {
	case vdl.Float32, vdl.Complex64:
	return 32
	case vdl.Float64, vdl.Complex128:
	return 64
	}
	panic(fmt.Errorf("vdl: bitLen unhandled kind %v", kind))
	}

	func genMethodTags(names typeNames, method *compile.Method) string {
	tags := method.Tags
	result := "["
	for _, tag := range tags {
	result += typedConst(names, tag) + ", "
	}
	result += "]"
	return result
	}

	// Format the given int64 into a JS BigInt.
	func formatUint64BigInt(v uint64) string {
	buffer := make([]byte, 8)
	binary.BigEndian.PutUint64(buffer, v)
	sign := "0"
	if v > 0 {
	sign = "1"
	}
	return fmt.Sprintf("new vdl.BigInt(%s, %s)", sign, formatByteBuffer(buffer))
	}

	// Format the given int64 into a JS BigInt.
	func formatInt64BigInt(v int64) string {
	buffer := make([]byte, 8)
	var sign int64 = 0
	if v > 0 {
	sign = 1
	} else if v < 0 {
	sign = -1
	}
	binary.BigEndian.PutUint64(buffer, uint64(v*sign)) // Adjust value by sign.

	return fmt.Sprintf("new vdl.BigInt(%d, %s)", sign, formatByteBuffer(buffer))
	}

	// Given a buffer of bytes, create the JS Uint8Array that corresponds to it (to be used with BigInt).
	func formatByteBuffer(buffer []byte) string {
	buf := bytes.TrimLeft(buffer, "\x00") // trim leading zeros
	str := "new Uint8Array(["
	for i, b := range buf {
	if i > 0 {
	str += ", "
	}
	str += fmt.Sprintf("%#x", b)
	}
	str += "])"
	return str
	}

	// untypedConst generates a javascript string representing a constant that is
	// not wrapped with type information.
	func untypedConst(names typeNames, v *vdl.Value) string {
	switch v.Kind() {
	case vdl.Bool:
	if v.Bool() {
	return "true"
	} else {
	return "false"
	}
	case vdl.Byte:
	return strconv.FormatUint(uint64(v.Byte()), 10)
	case vdl.Uint16, vdl.Uint32:
	return strconv.FormatUint(v.Uint(), 10)
	case vdl.Int16, vdl.Int32:
	return strconv.FormatInt(v.Int(), 10)
	case vdl.Uint64:
	return formatUint64BigInt(v.Uint())
	case vdl.Int64:
	return formatInt64BigInt(v.Int())
	case vdl.Float32, vdl.Float64:
	return strconv.FormatFloat(v.Float(), 'g', -1, bitlen(v.Kind()))
	case vdl.String:
	return strconv.Quote(v.RawString())
	case vdl.Any:
	if v.Elem() != nil {
	return typedConst(names, v.Elem())
	}
	return "null"
	case vdl.Optional:
	if v.Elem() != nil {
	return untypedConst(names, v.Elem())
	}
	return "null"
	case vdl.Complex64, vdl.Complex128:
	return fmt.Sprintf("new vdl.Complex(%f, %f)", real(v.Complex()), imag(v.Complex()))
	case vdl.Enum:
	return fmt.Sprintf("'%s'", v.EnumLabel())
	case vdl.Array, vdl.List:
	result := "["
	for ix := 0; ix < v.Len(); ix++ {
	val := untypedConst(names, v.Index(ix))
	result += "\n" + val + ","
	}
	result += "\n]"
	if v.Type().Elem().Kind() == vdl.Byte {
	return "new Uint8Array(" + result + ")"
	}
	return result
	case vdl.Set:
	result := "new Set(["
	for _, key := range vdl.SortValuesAsString(v.Keys()) {
	result += "\n " + untypedConst(names, key) + ", "
	}
	result += "])"
	return result
	case vdl.Map:
	result := "new Map(["
	for i, key := range vdl.SortValuesAsString(v.Keys()) {
	if i > 0 {
	result += ","
	}
	result += fmt.Sprintf("\n [%s, %s]",
	untypedConst(names, key),
	untypedConst(names, v.MapIndex(key)))

	}
	result += "])"
	return result
	case vdl.Struct:
	result := "{"
	t := v.Type()
	for ix := 0; ix < t.NumField(); ix++ {
	result += "\n '" +
	vdlutil.FirstRuneToLower(t.Field(ix).Name) +
	"': " +
	untypedConst(names, v.StructField(ix)) +
	","
	}
	return result + "\n}"
	case vdl.Union:
	ix, innerVal := v.UnionField()
	return fmt.Sprintf("{ %q: %v }", vdlutil.FirstRuneToLower(v.Type().Field(ix).Name), untypedConst(names, innerVal))
	case vdl.TypeObject:
	return names.LookupType(v.TypeObject())
	default:
	panic(fmt.Errorf("vdl: untypedConst unhandled type %v %v", v.Kind(), v.Type()))
	}
	}

	// typedConst returns a javascript string representing a const that is always
	// wrapped with type information
	func typedConst(names typeNames, v *vdl.Value) string {
	if v.Kind() == vdl.TypeObject \|\| v.Kind() == vdl.Any {
	return untypedConst(names, v)
	}
	if v.Kind() == vdl.Enum && names.IsDefinedInExternalPkg(v.Type()) {
	return fmt.Sprintf("%s.%s", qualifiedName(v.Type()), vdlutil.ToConstCase(v.EnumLabel()))
	}
	// We call canonicalize.reduce so that we convert to native types
	// The constructor would have done the reduction of the field values
	// but it doesn't convert to native types.
	return fmt.Sprintf("canonicalize.reduce(new %s(%s, true), %s)",
	names.LookupConstructor(v.Type()),
	untypedConst(names, v),
	names.LookupType(v.Type()))
	}

	// Returns a Not Implemented stub for the method
	func generateMethodStub(method *compile.Method) string {
	args := "ctx, serverCall"
	for _, arg := range method.InArgs {
	args += fmt.Sprintf(", %s", arg.Name)
	}

	return fmt.Sprintf(`function(%s) {
	throw new Error('Method %s not implemented');
	}`, args, method.Name)
	}

	// Returns the JS version of the method signature.
	func generateMethodSignature(method *compile.Method, names typeNames) string {
	return fmt.Sprintf(`{
	name: '%s',
	doc: %s,
	inArgs: %s,
	outArgs: %s,
	inStream: %s,
	outStream: %s,
	tags: %s
	}`,
	method.Name,
	quoteStripDoc(method.Doc),
	generateMethodArguments(method.InArgs, names),
	generateMethodArguments(method.OutArgs, names),
	generateMethodStreaming(method.InStream, names),
	generateMethodStreaming(method.OutStream, names),
	genMethodTags(names, method))
	}

	// Returns a slice describing the method's arguments.
	func generateMethodArguments(args []*compile.Field, names typeNames) string {
	ret := "["
	for _, arg := range args {
	ret += fmt.Sprintf(
	`{
	name: '%s',
	doc: %s,
	type: %s
	},
	`, arg.Name, quoteStripDoc(arg.Doc), names.LookupType(arg.Type))
	}
	ret += "]"
	return ret
	}

	// Returns the VOM type of the stream.
	func generateMethodStreaming(streaming *vdl.Type, names typeNames) string {
	if streaming == nil {
	return "null"
	}
	return fmt.Sprintf(
	`{
	name: '',
	doc: '',
	type: %s
	}`,
	names.LookupType(streaming))
	}

	// Returns a slice of embeddings with the proper qualified identifiers.
	func generateEmbeds(embeds []*compile.Interface) string {
	result := "["
	for _, embed := range embeds {
	result += fmt.Sprintf(`{
	name: '%s',
	pkgPath: '%s',
	doc: %s
	},
	`, embed.Name, embed.File.Package.Path, quoteStripDoc(embed.Doc))
	}
	result += "]"
	return result
	}

	func importPath(data data, path string) string {
	// We need to prefix all of these paths with a ./ to tell node that the path is relative to
	// the current directory. Sadly filepath.Join(".", foo) == foo, so we have to do it
	// explicitly.
	return "." + string(filepath.Separator) + data.GenerateImport(path)
	}

	func quoteStripDoc(doc string) string {
	// TODO(alexfandrianto): We need to handle '// ' and '\n' in the docstring.
	// It would also be nice to single-quote the whole string.
	trimmed := strings.Trim(doc, "\n")
	return strconv.Quote(trimmed)
	}

	func hasErrors(pkg *compile.Package) bool {
	for _, file := range pkg.Files {
	if len(file.ErrorDefs) > 0 {
	return true
	}
	}
	return false
	}

	func hasConsts(pkg *compile.Package) bool {
	for _, file := range pkg.Files {
	if len(file.ConstDefs) > 0 {
	return true
	}
	}
	return false
	}

	func hasEnums(pkg *compile.Package) bool {
	for _, file := range pkg.Files {
	for _, def := range file.TypeDefs {
	if def.Type.Kind() == vdl.Enum {
	return true
	}
	}
	}
	return false
	}

	func hasMethodTags(pkg *compile.Package) bool {
	for _, file := range pkg.Files {
	for _, iface := range file.Interfaces {
	for _, method := range iface.Methods {
	if len(method.Tags) > 0 {
	return true
	}
	}
	}
	}
	return false
	}

	func generateSystemImports(data data) string {
	res := "var vdl = require('"
	packagePrefix := ""
	if data.PathToCoreJS != "" {
	packagePrefix = strings.Repeat("../", strings.Count(data.Pkg.Path, "/")+1) + data.PathToCoreJS
	}
	if data.PathToCoreJS != "" {
	res += packagePrefix + "/vdl');"
	} else {
	res += "vanadium').vdl;"
	}
	res += "\n"
	if hasErrors(data.Pkg) {
	if data.PathToCoreJS != "" {
	res += "var makeError = require('" + packagePrefix + "/verror/make-errors');\n"
	res += "var actions = require('" + packagePrefix + "/verror/actions');\n"
	} else {
	res += "var makeError = require('vanadium').verror.makeError;\n"
	res += "var actions = require('vanadium').verror.actions;\n"
	}
	}

	if hasConsts(data.Pkg) \|\| hasEnums(data.Pkg) \|\| hasMethodTags(data.Pkg) {
	if data.PathToCoreJS != "" {
	res += "var canonicalize = require('" + packagePrefix + "/vdl/canonicalize');\n"
	} else {
	res += "var canonicalize = require('vanadium').vdl.canonicalize;\n"
	}
	}
	return res
	}

	func init() {
	funcMap := template.FuncMap{
	"firstRuneToLower": vdlutil.FirstRuneToLower,
	"genMethodTags": genMethodTags,
	"makeTypeDefinitionsString": makeTypeDefinitionsString,
	"typedConst": typedConst,
	"generateEmbeds": generateEmbeds,
	"generateMethodStub": generateMethodStub,
	"generateMethodSignature": generateMethodSignature,
	"importPath": importPath,
	"quoteStripDoc": quoteStripDoc,
	"generateErrorConstructor": generateErrorConstructor,
	"generateSystemImports": generateSystemImports,
	}
	javascriptTemplate = template.Must(template.New("genJS").Funcs(funcMap).Parse(genJS))
	}

	// The template that we execute against a compile.Package instance to generate our
	// code. Most of this is fairly straightforward substitution and ranges; more
	// complicated logic is delegated to the helper functions above.
	//
	// We try to generate code that has somewhat reasonable formatting.
	const genJS = `{{with $data := .}}{{$data.Pkg.FileDoc}}
	// This file was auto-generated by the vanadium vdl tool.
	{{generateSystemImports $data}}

	{{/* Define additional imported modules. */}}
	{{$pkg := $data.Pkg}}
	{{if $data.UserImports}}{{range $imp := $data.UserImports}}
	var {{$imp.Local}} = require('{{importPath $data $imp.Path}}');{{end}}{{end}}

	module.exports = {};


	{{/* Define any types introduced by the VDL file. */}}
	// Types:
	{{makeTypeDefinitionsString $data.TypeNames }}


	{{/* Define all constants as typed constants. */}}
	// Consts:
	{{range $file := $pkg.Files}}{{range $const := $file.ConstDefs}}
	module.exports.{{$const.Name}} = {{typedConst $data.TypeNames $const.Value}};
	{{end}}{{end}}

	{{/* Define all errors. */}}
	// Errors:
	{{range $file := $pkg.Files}}{{range $error := $file.ErrorDefs}}
	{{generateErrorConstructor $data.TypeNames $error}}
	{{end}}{{end}}

	{{/* Define each of those service interfaces here, including method stubs and
	service signature. */}}
	// Services:
	{{range $file := $pkg.Files}}
	{{range $iface := $file.Interfaces}}
	{{/* Define the service interface. */}}
	function {{$iface.Name}}(){}
	module.exports.{{$iface.Name}} = {{$iface.Name}};

	{{range $method := $iface.AllMethods}}
	{{/* Add each method to the service prototype. */}}
	{{$iface.Name}}.prototype.{{firstRuneToLower $method.Name}} = {{generateMethodStub $method}};
	{{end}} {{/* end range $iface.AllMethods */}}

	{{/* The service signature encodes the same info as signature.Interface.
	TODO(alexfandrianto): We want to associate the signature type here, but
	it's complicated.
	For now, we need to pass the type in manually into encode. */}}
	{{$iface.Name}}.prototype._serviceDescription = {
	name: '{{$iface.Name}}',
	pkgPath: '{{$pkg.Path}}',
	doc: {{quoteStripDoc $iface.Doc}},
	embeds: {{generateEmbeds $iface.Embeds}},
	methods: [
	{{range $method := $iface.AllMethods}}
	{{/* Each method signature contains the information in rpc.MethodSig. */}}
	{{generateMethodSignature $method $data.TypeNames}},
	{{end}} {{/end range $iface.AllMethods/}}
	]
	};

	{{end}} {{/* end range $files.Interfaces */}}
	{{end}} {{/* end range $pkg.Files */}}


	{{end}}`