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generator.go
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generator.go
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// Copyright 2018 Twitch Interactive, Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"). You may not
// use this file except in compliance with the License. A copy of the License is
// located at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// or in the "license" file accompanying this file. This file 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 (
"bufio"
"bytes"
"compress/gzip"
"fmt"
"go/parser"
"go/printer"
"go/token"
"path"
"strconv"
"strings"
"github.com/golang/protobuf/proto"
"github.com/golang/protobuf/protoc-gen-go/descriptor"
plugin "github.com/golang/protobuf/protoc-gen-go/plugin"
"github.com/pkg/errors"
"github.com/twitchtv/twirp/internal/gen"
"github.com/twitchtv/twirp/internal/gen/stringutils"
"github.com/twitchtv/twirp/internal/gen/typemap"
)
type twirp struct {
filesHandled int
currentPackage string // Go name of current package we're working on
reg *typemap.Registry
// Map to record whether we've built each package
pkgs map[string]string
pkgNamesInUse map[string]bool
// Package naming:
genPkgName string // Name of the package that we're generating
fileToGoPackageName map[*descriptor.FileDescriptorProto]string
// List of files that were inputs to the generator. We need to hold this in
// the struct so we can write a header for the file that lists its inputs.
genFiles []*descriptor.FileDescriptorProto
// Output buffer that holds the bytes we want to write out for a single file.
// Gets reset after working on a file.
output *bytes.Buffer
}
func newGenerator() *twirp {
t := &twirp{
pkgs: make(map[string]string),
pkgNamesInUse: make(map[string]bool),
fileToGoPackageName: make(map[*descriptor.FileDescriptorProto]string),
output: bytes.NewBuffer(nil),
}
return t
}
func (t *twirp) Generate(in *plugin.CodeGeneratorRequest) *plugin.CodeGeneratorResponse {
t.genFiles = gen.FilesToGenerate(in)
// Collect information on types.
t.reg = typemap.New(in.ProtoFile)
// Register names of packages that we import.
t.registerPackageName("bytes")
t.registerPackageName("strings")
t.registerPackageName("ctxsetters")
t.registerPackageName("context")
t.registerPackageName("http")
t.registerPackageName("io")
t.registerPackageName("ioutil")
t.registerPackageName("json")
t.registerPackageName("jsonpb")
t.registerPackageName("log")
t.registerPackageName("proto")
t.registerPackageName("strconv")
t.registerPackageName("twirp")
t.registerPackageName("url")
t.registerPackageName("fmt")
// Time to figure out package names of objects defined in protobuf. First,
// we'll figure out the name for the package we're generating.
genPkgName, err := deduceGenPkgName(t.genFiles)
if err != nil {
gen.Fail(err.Error())
}
t.genPkgName = genPkgName
// Next, we need to pick names for all the files that are dependencies.
for _, f := range in.ProtoFile {
if fileDescSliceContains(t.genFiles, f) {
// This is a file we are generating. It gets the shared package name.
t.fileToGoPackageName[f] = t.genPkgName
} else {
// This is a dependency. Use its package name.
name := f.GetPackage()
if name == "" {
name = stringutils.BaseName(f.GetName())
}
name = stringutils.CleanIdentifier(name)
t.fileToGoPackageName[f] = name
t.registerPackageName(name)
}
}
// Showtime! Generate the response.
resp := new(plugin.CodeGeneratorResponse)
for _, f := range t.genFiles {
respFile := t.generate(f)
if respFile != nil {
resp.File = append(resp.File, respFile)
}
}
return resp
}
func (t *twirp) registerPackageName(name string) (alias string) {
alias = name
i := 1
for t.pkgNamesInUse[alias] {
alias = name + strconv.Itoa(i)
i++
}
t.pkgNamesInUse[alias] = true
t.pkgs[name] = alias
return alias
}
// deduceGenPkgName figures out the go package name to use for generated code.
// Will try to use the explicit go_package setting in a file (if set, must be
// consistent in all files). If no files have go_package set, then use the
// protobuf package name (must be consistent in all files)
func deduceGenPkgName(genFiles []*descriptor.FileDescriptorProto) (string, error) {
var genPkgName string
for _, f := range genFiles {
name, explicit := goPackageName(f)
if explicit {
name = stringutils.CleanIdentifier(name)
if genPkgName != "" && genPkgName != name {
// Make sure they're all set consistently.
return "", errors.Errorf("files have conflicting go_package settings, must be the same: %q and %q", genPkgName, name)
}
genPkgName = name
}
}
if genPkgName != "" {
return genPkgName, nil
}
// If there is no explicit setting, then check the implicit package name
// (derived from the protobuf package name) of the files and make sure it's
// consistent.
for _, f := range genFiles {
name, _ := goPackageName(f)
name = stringutils.CleanIdentifier(name)
if genPkgName != "" && genPkgName != name {
return "", errors.Errorf("files have conflicting package names, must be the same or overridden with go_package: %q and %q", genPkgName, name)
}
genPkgName = name
}
// All the files have the same name, so we're good.
return genPkgName, nil
}
func (t *twirp) generate(file *descriptor.FileDescriptorProto) *plugin.CodeGeneratorResponse_File {
resp := new(plugin.CodeGeneratorResponse_File)
if len(file.Service) == 0 {
return nil
}
t.generateFileHeader(file)
t.generateImports(file)
if t.filesHandled == 0 {
t.generateUtilImports()
}
// For each service, generate client stubs and server
for i, service := range file.Service {
t.generateService(file, service, i)
}
// Util functions only generated once per package
if t.filesHandled == 0 {
t.generateUtils()
}
t.generateFileDescriptor(file)
resp.Name = proto.String(goFileName(file))
resp.Content = proto.String(t.formattedOutput())
t.output.Reset()
t.filesHandled++
return resp
}
func (t *twirp) generateFileHeader(file *descriptor.FileDescriptorProto) {
t.P("// Code generated by protoc-gen-twirp ", gen.Version, ", DO NOT EDIT.")
t.P("// source: ", file.GetName())
t.P()
if t.filesHandled == 0 {
t.P("/*")
t.P("Package ", t.genPkgName, " is a generated twirp stub package.")
t.P("This code was generated with github.com/twitchtv/twirp/protoc-gen-twirp ", gen.Version, ".")
t.P()
comment, err := t.reg.FileComments(file)
if err == nil && comment.Leading != "" {
for _, line := range strings.Split(comment.Leading, "\n") {
line = strings.TrimPrefix(line, " ")
// ensure we don't escape from the block comment
line = strings.Replace(line, "*/", "* /", -1)
t.P(line)
}
t.P()
}
t.P("It is generated from these files:")
for _, f := range t.genFiles {
t.P("\t", f.GetName())
}
t.P("*/")
}
t.P(`package `, t.genPkgName)
t.P()
}
func (t *twirp) generateImports(file *descriptor.FileDescriptorProto) {
if len(file.Service) == 0 {
return
}
t.P(`import `, t.pkgs["bytes"], ` "bytes"`)
t.P(`import `, t.pkgs["context"], ` "context"`)
t.P(`import `, t.pkgs["fmt"], ` "fmt"`)
t.P(`import `, t.pkgs["ioutil"], ` "io/ioutil"`)
t.P(`import `, t.pkgs["log"], ` "log"`)
t.P(`import `, t.pkgs["http"], ` "net/http"`)
t.P()
t.P(`import `, t.pkgs["jsonpb"], ` "github.com/golang/protobuf/jsonpb"`)
t.P(`import `, t.pkgs["proto"], ` "github.com/golang/protobuf/proto"`)
t.P(`import `, t.pkgs["twirp"], ` "github.com/twitchtv/twirp"`)
t.P(`import `, t.pkgs["ctxsetters"], ` "github.com/twitchtv/twirp/ctxsetters"`)
t.P()
// It's legal to import a message and use it as an input or output for a
// method. Make sure to import the package of any such message. First, dedupe
// them.
deps := make(map[string]string) // Map of package name to quoted import path.
ourImportPath := path.Dir(goFileName(file))
for _, s := range file.Service {
for _, m := range s.Method {
defs := []*typemap.MessageDefinition{
t.reg.MethodInputDefinition(m),
t.reg.MethodOutputDefinition(m),
}
for _, def := range defs {
importPath := path.Dir(goFileName(def.File))
if importPath != ourImportPath {
pkg := t.goPackageName(def.File)
deps[pkg] = strconv.Quote(importPath)
}
}
}
}
for pkg, importPath := range deps {
t.P(`import `, pkg, ` `, importPath)
}
if len(deps) > 0 {
t.P()
}
}
func (t *twirp) generateUtilImports() {
t.P("// Imports only used by utility functions:")
t.P(`import `, t.pkgs["io"], ` "io"`)
t.P(`import `, t.pkgs["strconv"], ` "strconv"`)
t.P(`import `, t.pkgs["json"], ` "encoding/json"`)
t.P(`import `, t.pkgs["url"], ` "net/url"`)
}
// Generate utility functions used in Twirp code.
// These should be generated just once per package.
func (t *twirp) generateUtils() {
t.sectionComment(`Utils`)
t.P(`// HTTPClient is the interface used by generated clients to send HTTP requests.`)
t.P(`// It is fulfilled by *(net/http).Client, which is sufficient for most users.`)
t.P(`// Users can provide their own implementation for special retry policies.`)
t.P(`// `)
t.P(`// HTTPClient implementations should not follow redirects. Redirects are`)
t.P(`// automatically disabled if *(net/http).Client is passed to client`)
t.P(`// constructors. See the withoutRedirects function in this file for more`)
t.P(`// details.`)
t.P(`type HTTPClient interface {`)
t.P(` Do(req *`, t.pkgs["http"], `.Request) (*`, t.pkgs["http"], `.Response, error)`)
t.P(`}`)
t.P()
t.P(`// TwirpServer is the interface generated server structs will support: they're`)
t.P(`// HTTP handlers with additional methods for accessing metadata about the`)
t.P(`// service. Those accessors are a low-level API for building reflection tools.`)
t.P(`// Most people can think of TwirpServers as just http.Handlers.`)
t.P(`type TwirpServer interface {`)
t.P(` `, t.pkgs["http"], `.Handler`)
t.P(` // ServiceDescriptor returns gzipped bytes describing the .proto file that`)
t.P(` // this service was generated from. Once unzipped, the bytes can be`)
t.P(` // unmarshalled as a`)
t.P(` // github.com/golang/protobuf/protoc-gen-go/descriptor.FileDescriptorProto.`)
t.P(` //`)
t.P(` // The returned integer is the index of this particular service within that`)
t.P(` // FileDescriptorProto's 'Service' slice of ServiceDescriptorProtos. This is a`)
t.P(` // low-level field, expected to be used for reflection.`)
t.P(` ServiceDescriptor() ([]byte, int)`)
t.P(` // ProtocGenTwirpVersion is the semantic version string of the version of`)
t.P(` // twirp used to generate this file.`)
t.P(` ProtocGenTwirpVersion() string`)
t.P(`}`)
t.P()
t.P(`// WriteError writes an HTTP response with a valid Twirp error format.`)
t.P(`// If err is not a twirp.Error, it will get wrapped with twirp.InternalErrorWith(err)`)
t.P(`func WriteError(resp `, t.pkgs["http"], `.ResponseWriter, err error) {`)
t.P(` writeError(`, t.pkgs["context"], `.Background(), resp, err, nil)`)
t.P(`}`)
t.P()
t.P(`// writeError writes Twirp errors in the response and triggers hooks.`)
t.P(`func writeError(ctx `, t.pkgs["context"], `.Context, resp `, t.pkgs["http"], `.ResponseWriter, err error, hooks *`, t.pkgs["twirp"], `.ServerHooks) {`)
t.P(` // Non-twirp errors are wrapped as Internal (default)`)
t.P(` twerr, ok := err.(`, t.pkgs["twirp"], `.Error)`)
t.P(` if !ok {`)
t.P(` twerr = `, t.pkgs["twirp"], `.InternalErrorWith(err)`)
t.P(` }`)
t.P(``)
t.P(` statusCode := `, t.pkgs["twirp"], `.ServerHTTPStatusFromErrorCode(twerr.Code())`)
t.P(` ctx = `, t.pkgs["ctxsetters"], `.WithStatusCode(ctx, statusCode)`)
t.P(` ctx = callError(ctx, hooks, twerr)`)
t.P(``)
t.P(` resp.Header().Set("Content-Type", "application/json") // Error responses are always JSON (instead of protobuf)`)
t.P(` resp.WriteHeader(statusCode) // HTTP response status code`)
t.P(``)
t.P(` respBody := marshalErrorToJSON(twerr)`)
t.P(` _, err2 := resp.Write(respBody)`)
t.P(` if err2 != nil {`)
t.P(` `, t.pkgs["log"], `.Printf("unable to send error message %q: %s", twerr, err2)`)
t.P(` }`)
t.P(``)
t.P(` callResponseSent(ctx, hooks)`)
t.P(`}`)
t.P()
t.P(`// urlBase helps ensure that addr specifies a scheme. If it is unparsable`)
t.P(`// as a URL, it returns addr unchanged.`)
t.P(`func urlBase(addr string) string {`)
t.P(` // If the addr specifies a scheme, use it. If not, default to`)
t.P(` // http. If url.Parse fails on it, return it unchanged.`)
t.P(` url, err := `, t.pkgs["url"], `.Parse(addr)`)
t.P(` if err != nil {`)
t.P(` return addr`)
t.P(` }`)
t.P(` if url.Scheme == "" {`)
t.P(` url.Scheme = "http"`)
t.P(` }`)
t.P(` return url.String()`)
t.P(`}`)
t.P()
t.P(`// getCustomHTTPReqHeaders retrieves a copy of any headers that are set in`)
t.P(`// a context through the twirp.WithHTTPRequestHeaders function.`)
t.P(`// If there are no headers set, or if they have the wrong type, nil is returned.`)
t.P(`func getCustomHTTPReqHeaders(ctx `, t.pkgs["context"], `.Context) `, t.pkgs["http"], `.Header {`)
t.P(` header, ok := `, t.pkgs["twirp"], `.HTTPRequestHeaders(ctx)`)
t.P(` if !ok || header == nil {`)
t.P(` return nil`)
t.P(` }`)
t.P(` copied := make(`, t.pkgs["http"], `.Header)`)
t.P(` for k, vv := range header {`)
t.P(` if vv == nil {`)
t.P(` copied[k] = nil`)
t.P(` continue`)
t.P(` }`)
t.P(` copied[k] = make([]string, len(vv))`)
t.P(` copy(copied[k], vv)`)
t.P(` }`)
t.P(` return copied`)
t.P(`}`)
t.P()
t.P(`// closebody closes a response or request body and just logs `)
t.P(`// any error encountered while closing, since errors are `)
t.P(`// considered very unusual.`)
t.P(`func closebody(body io.Closer) {`)
t.P(` if err := body.Close(); err != nil {`)
t.P(` `, t.pkgs["log"], `.Printf("error closing body: %q", err)`)
t.P(` }`)
t.P(`}`)
t.P()
t.P(`// newRequest makes an http.Request from a client, adding common headers.`)
t.P(`func newRequest(ctx `, t.pkgs["context"], `.Context, url string, reqBody io.Reader, contentType string) (*`, t.pkgs["http"], `.Request, error) {`)
t.P(` req, err := `, t.pkgs["http"], `.NewRequest("POST", url, reqBody)`)
t.P(` if err != nil {`)
t.P(` return nil, err`)
t.P(` }`)
t.P(` req = req.WithContext(ctx)`)
t.P(` if customHeader := getCustomHTTPReqHeaders(ctx); customHeader != nil {`)
t.P(` req.Header = customHeader`)
t.P(` }`)
t.P(` req.Header.Set("Content-Type", contentType)`)
t.P(` req.Header.Set("Twirp-Version", "`, gen.Version, `")`)
t.P(` return req, nil`)
t.P(`}`)
t.P(`// JSON serialization for errors`)
t.P(`type twerrJSON struct {`)
t.P(" Code string `json:\"code\"`")
t.P(" Msg string `json:\"msg\"`")
t.P(" Meta map[string]string `json:\"meta,omitempty\"`")
t.P(`}`)
t.P()
t.P(`// marshalErrorToJSON returns JSON from a twirp.Error, that can be used as HTTP error response body.`)
t.P(`// If serialization fails, it will use a descriptive Internal error instead.`)
t.P(`func marshalErrorToJSON(twerr `, t.pkgs["twirp"], `.Error) []byte {`)
t.P(` // make sure that msg is not too large`)
t.P(` msg := twerr.Msg()`)
t.P(` if len(msg) > 1e6 {`)
t.P(` msg = msg[:1e6]`)
t.P(` }`)
t.P(``)
t.P(` tj := twerrJSON{`)
t.P(` Code: string(twerr.Code()),`)
t.P(` Msg: msg,`)
t.P(` Meta: twerr.MetaMap(),`)
t.P(` }`)
t.P(``)
t.P(` buf, err := `, t.pkgs["json"], `.Marshal(&tj)`)
t.P(` if err != nil {`)
t.P(` buf = []byte("{\"type\": \"" + `, t.pkgs["twirp"], `.Internal +"\", \"msg\": \"There was an error but it could not be serialized into JSON\"}") // fallback`)
t.P(` }`)
t.P(``)
t.P(` return buf`)
t.P(`}`)
t.P()
t.P(`// errorFromResponse builds a twirp.Error from a non-200 HTTP response.`)
t.P(`// If the response has a valid serialized Twirp error, then it's returned.`)
t.P(`// If not, the response status code is used to generate a similar twirp`)
t.P(`// error. See twirpErrorFromIntermediary for more info on intermediary errors.`)
t.P(`func errorFromResponse(resp *`, t.pkgs["http"], `.Response) `, t.pkgs["twirp"], `.Error {`)
t.P(` statusCode := resp.StatusCode`)
t.P(` statusText := `, t.pkgs["http"], `.StatusText(statusCode)`)
t.P(``)
t.P(` if isHTTPRedirect(statusCode) {`)
t.P(` // Unexpected redirect: it must be an error from an intermediary.`)
t.P(` // Twirp clients don't follow redirects automatically, Twirp only handles`)
t.P(` // POST requests, redirects should only happen on GET and HEAD requests.`)
t.P(` location := resp.Header.Get("Location")`)
t.P(` msg := `, t.pkgs["fmt"], `.Sprintf("unexpected HTTP status code %d %q received, Location=%q", statusCode, statusText, location)`)
t.P(` return twirpErrorFromIntermediary(statusCode, msg, location)`)
t.P(` }`)
t.P(``)
t.P(` respBodyBytes, err := `, t.pkgs["ioutil"], `.ReadAll(resp.Body)`)
t.P(` if err != nil {`)
t.P(` return clientError("failed to read server error response body", err)`)
t.P(` }`)
t.P(` var tj twerrJSON`)
t.P(` if err := `, t.pkgs["json"], `.Unmarshal(respBodyBytes, &tj); err != nil {`)
t.P(` // Invalid JSON response; it must be an error from an intermediary.`)
t.P(` msg := `, t.pkgs["fmt"], `.Sprintf("Error from intermediary with HTTP status code %d %q", statusCode, statusText)`)
t.P(` return twirpErrorFromIntermediary(statusCode, msg, string(respBodyBytes))`)
t.P(` }`)
t.P(``)
t.P(` errorCode := `, t.pkgs["twirp"], `.ErrorCode(tj.Code)`)
t.P(` if !`, t.pkgs["twirp"], `.IsValidErrorCode(errorCode) {`)
t.P(` msg := "invalid type returned from server error response: "+tj.Code`)
t.P(` return `, t.pkgs["twirp"], `.InternalError(msg)`)
t.P(` }`)
t.P(``)
t.P(` twerr := `, t.pkgs["twirp"], `.NewError(errorCode, tj.Msg)`)
t.P(` for k, v := range(tj.Meta) {`)
t.P(` twerr = twerr.WithMeta(k, v)`)
t.P(` }`)
t.P(` return twerr`)
t.P(`}`)
t.P()
t.P(`// twirpErrorFromIntermediary maps HTTP errors from non-twirp sources to twirp errors.`)
t.P(`// The mapping is similar to gRPC: https://github.com/grpc/grpc/blob/master/doc/http-grpc-status-mapping.md.`)
t.P(`// Returned twirp Errors have some additional metadata for inspection.`)
t.P(`func twirpErrorFromIntermediary(status int, msg string, bodyOrLocation string) `, t.pkgs["twirp"], `.Error {`)
t.P(` var code `, t.pkgs["twirp"], `.ErrorCode`)
t.P(` if isHTTPRedirect(status) { // 3xx`)
t.P(` code = `, t.pkgs["twirp"], `.Internal`)
t.P(` } else {`)
t.P(` switch status {`)
t.P(` case 400: // Bad Request`)
t.P(` code = `, t.pkgs["twirp"], `.Internal`)
t.P(` case 401: // Unauthorized`)
t.P(` code = `, t.pkgs["twirp"], `.Unauthenticated`)
t.P(` case 403: // Forbidden`)
t.P(` code = `, t.pkgs["twirp"], `.PermissionDenied`)
t.P(` case 404: // Not Found`)
t.P(` code = `, t.pkgs["twirp"], `.BadRoute`)
t.P(` case 429, 502, 503, 504: // Too Many Requests, Bad Gateway, Service Unavailable, Gateway Timeout`)
t.P(` code = `, t.pkgs["twirp"], `.Unavailable`)
t.P(` default: // All other codes`)
t.P(` code = `, t.pkgs["twirp"], `.Unknown`)
t.P(` }`)
t.P(` }`)
t.P(``)
t.P(` twerr := `, t.pkgs["twirp"], `.NewError(code, msg)`)
t.P(` twerr = twerr.WithMeta("http_error_from_intermediary", "true") // to easily know if this error was from intermediary`)
t.P(` twerr = twerr.WithMeta("status_code", `, t.pkgs["strconv"], `.Itoa(status))`)
t.P(` if isHTTPRedirect(status) {`)
t.P(` twerr = twerr.WithMeta("location", bodyOrLocation)`)
t.P(` } else {`)
t.P(` twerr = twerr.WithMeta("body", bodyOrLocation)`)
t.P(` }`)
t.P(` return twerr`)
t.P(`}`)
t.P(`func isHTTPRedirect(status int) bool {`)
t.P(` return status >= 300 && status <= 399`)
t.P(`}`)
t.P(`// wrappedError implements the github.com/pkg/errors.Causer interface, allowing errors to be`)
t.P(`// examined for their root cause.`)
t.P(`type wrappedError struct {`)
t.P(` msg string`)
t.P(` cause error`)
t.P(`}`)
t.P()
t.P(`func wrapErr(err error, msg string) error { return &wrappedError{msg: msg, cause: err} }`)
t.P(`func (e *wrappedError) Cause() error { return e.cause }`)
t.P(`func (e *wrappedError) Error() string { return e.msg + ": " + e.cause.Error() }`)
t.P()
t.P(`// clientError adds consistency to errors generated in the client`)
t.P(`func clientError(desc string, err error) `, t.pkgs["twirp"], `.Error {`)
t.P(` return `, t.pkgs["twirp"], `.InternalErrorWith(wrapErr(err, desc))`)
t.P(`}`)
t.P()
t.P(`// badRouteError is used when the twirp server cannot route a request`)
t.P(`func badRouteError(msg string, method, url string) `, t.pkgs["twirp"], `.Error {`)
t.P(` err := `, t.pkgs["twirp"], `.NewError(`, t.pkgs["twirp"], `.BadRoute, msg)`)
t.P(` err = err.WithMeta("twirp_invalid_route", method+" "+url)`)
t.P(` return err`)
t.P(`}`)
t.P()
t.P(`// The standard library will, by default, redirect requests (including POSTs) if it gets a 302 or`)
t.P(`// 303 response, and also 301s in go1.8. It redirects by making a second request, changing the`)
t.P(`// method to GET and removing the body. This produces very confusing error messages, so instead we`)
t.P(`// set a redirect policy that always errors. This stops Go from executing the redirect.`)
t.P(`//`)
t.P(`// We have to be a little careful in case the user-provided http.Client has its own CheckRedirect`)
t.P(`// policy - if so, we'll run through that policy first.`)
t.P(`//`)
t.P(`// Because this requires modifying the http.Client, we make a new copy of the client and return it.`)
t.P(`func withoutRedirects(in *`, t.pkgs["http"], `.Client) *`, t.pkgs["http"], `.Client {`)
t.P(` copy := *in`)
t.P(` copy.CheckRedirect = func(req *`, t.pkgs["http"], `.Request, via []*`, t.pkgs["http"], `.Request) error {`)
t.P(` if in.CheckRedirect != nil {`)
t.P(` // Run the input's redirect if it exists, in case it has side effects, but ignore any error it`)
t.P(` // returns, since we want to use ErrUseLastResponse.`)
t.P(` err := in.CheckRedirect(req, via)`)
t.P(` _ = err // Silly, but this makes sure generated code passes errcheck -blank, which some people use.`)
t.P(` }`)
t.P(` return `, t.pkgs["http"], `.ErrUseLastResponse`)
t.P(` }`)
t.P(` return ©`)
t.P(`}`)
t.P()
t.P(`// doProtoRequest is common code to make a request to the remote twirp service.`)
t.P(`func doProtoRequest(ctx `, t.pkgs["context"], `.Context, client HTTPClient, url string, in, out `, t.pkgs["proto"], `.Message) error {`)
t.P(` var err error`)
t.P(` reqBodyBytes, err := `, t.pkgs["proto"], `.Marshal(in)`)
t.P(` if err != nil {`)
t.P(` return clientError("failed to marshal proto request", err)`)
t.P(` }`)
t.P(` reqBody := `, t.pkgs["bytes"], `.NewBuffer(reqBodyBytes)`)
t.P(` if err = ctx.Err(); err != nil {`)
t.P(` return clientError("aborted because context was done", err)`)
t.P(` }`)
t.P()
t.P(` req, err := newRequest(ctx, url, reqBody, "application/protobuf")`)
t.P(` if err != nil {`)
t.P(` return clientError("could not build request", err)`)
t.P(` }`)
t.P(` resp, err := client.Do(req)`)
t.P(` if err != nil {`)
t.P(` return clientError("failed to do request", err)`)
t.P(` }`)
t.P(` defer closebody(resp.Body)`)
t.P(` if err = ctx.Err(); err != nil {`)
t.P(` return clientError("aborted because context was done", err)`)
t.P(` }`)
t.P()
t.P(` if resp.StatusCode != 200 {`)
t.P(` return errorFromResponse(resp)`)
t.P(` }`)
t.P()
t.P(` respBodyBytes, err := `, t.pkgs["ioutil"], `.ReadAll(resp.Body)`)
t.P(` if err != nil {`)
t.P(` return clientError("failed to read response body", err)`)
t.P(` }`)
t.P(` if err = ctx.Err(); err != nil {`)
t.P(` return clientError("aborted because context was done", err)`)
t.P(` }`)
t.P()
t.P(` if err = `, t.pkgs["proto"], `.Unmarshal(respBodyBytes, out); err != nil {`)
t.P(` return clientError("failed to unmarshal proto response", err)`)
t.P(` }`)
t.P(` return nil`)
t.P(`}`)
t.P()
t.P(`// doJSONRequest is common code to make a request to the remote twirp service.`)
t.P(`func doJSONRequest(ctx `, t.pkgs["context"], `.Context, client HTTPClient, url string, in, out `, t.pkgs["proto"], `.Message) error {`)
t.P(` var err error`)
t.P(` reqBody := `, t.pkgs["bytes"], `.NewBuffer(nil)`)
t.P(` marshaler := &`, t.pkgs["jsonpb"], `.Marshaler{OrigName: true}`)
t.P(` if err = marshaler.Marshal(reqBody, in); err != nil {`)
t.P(` return clientError("failed to marshal json request", err)`)
t.P(` }`)
t.P(` if err = ctx.Err(); err != nil {`)
t.P(` return clientError("aborted because context was done", err)`)
t.P(` }`)
t.P()
t.P(` req, err := newRequest(ctx, url, reqBody, "application/json")`)
t.P(` if err != nil {`)
t.P(` return clientError("could not build request", err)`)
t.P(` }`)
t.P(` resp, err := client.Do(req)`)
t.P(` if err != nil {`)
t.P(` return clientError("failed to do request", err)`)
t.P(` }`)
t.P(` defer closebody(resp.Body)`)
t.P(` if err = ctx.Err(); err != nil {`)
t.P(` return clientError("aborted because context was done", err)`)
t.P(` }`)
t.P()
t.P(` if resp.StatusCode != 200 {`)
t.P(` return errorFromResponse(resp)`)
t.P(` }`)
t.P()
t.P(` unmarshaler := `, t.pkgs["jsonpb"], `.Unmarshaler{AllowUnknownFields: true}`)
t.P(` if err = unmarshaler.Unmarshal(resp.Body, out); err != nil {`)
t.P(` return clientError("failed to unmarshal json response", err)`)
t.P(` }`)
t.P(` if err = ctx.Err(); err != nil {`)
t.P(` return clientError("aborted because context was done", err)`)
t.P(` }`)
t.P(` return nil`)
t.P(`}`)
t.P()
t.P(`// Call twirp.ServerHooks.RequestReceived if the hook is available`)
t.P(`func callRequestReceived(ctx `, t.pkgs["context"], `.Context, h *`, t.pkgs["twirp"], `.ServerHooks) (`, t.pkgs["context"], `.Context, error) {`)
t.P(` if h == nil || h.RequestReceived == nil {`)
t.P(` return ctx, nil`)
t.P(` }`)
t.P(` return h.RequestReceived(ctx)`)
t.P(`}`)
t.P()
t.P(`// Call twirp.ServerHooks.RequestRouted if the hook is available`)
t.P(`func callRequestRouted(ctx `, t.pkgs["context"], `.Context, h *`, t.pkgs["twirp"], `.ServerHooks) (`, t.pkgs["context"], `.Context, error) {`)
t.P(` if h == nil || h.RequestRouted == nil {`)
t.P(` return ctx, nil`)
t.P(` }`)
t.P(` return h.RequestRouted(ctx)`)
t.P(`}`)
t.P()
t.P(`// Call twirp.ServerHooks.ResponsePrepared if the hook is available`)
t.P(`func callResponsePrepared(ctx `, t.pkgs["context"], `.Context, h *`, t.pkgs["twirp"], `.ServerHooks) `, t.pkgs["context"], `.Context {`)
t.P(` if h == nil || h.ResponsePrepared == nil {`)
t.P(` return ctx`)
t.P(` }`)
t.P(` return h.ResponsePrepared(ctx)`)
t.P(`}`)
t.P()
t.P(`// Call twirp.ServerHooks.ResponseSent if the hook is available`)
t.P(`func callResponseSent(ctx `, t.pkgs["context"], `.Context, h *`, t.pkgs["twirp"], `.ServerHooks) {`)
t.P(` if h == nil || h.ResponseSent == nil {`)
t.P(` return`)
t.P(` }`)
t.P(` h.ResponseSent(ctx)`)
t.P(`}`)
t.P()
t.P(`// Call twirp.ServerHooks.Error if the hook is available`)
t.P(`func callError(ctx `, t.pkgs["context"], `.Context, h *`, t.pkgs["twirp"], `.ServerHooks, err `, t.pkgs["twirp"], `.Error) `, t.pkgs["context"], `.Context {`)
t.P(` if h == nil || h.Error == nil {`)
t.P(` return ctx`)
t.P(` }`)
t.P(` return h.Error(ctx, err)`)
t.P(`}`)
t.P()
}
// P forwards to g.gen.P, which prints output.
func (t *twirp) P(args ...string) {
for _, v := range args {
t.output.WriteString(v)
}
t.output.WriteByte('\n')
}
// Big header comments to makes it easier to visually parse a generated file.
func (t *twirp) sectionComment(sectionTitle string) {
t.P()
t.P(`// `, strings.Repeat("=", len(sectionTitle)))
t.P(`// `, sectionTitle)
t.P(`// `, strings.Repeat("=", len(sectionTitle)))
t.P()
}
func (t *twirp) generateService(file *descriptor.FileDescriptorProto, service *descriptor.ServiceDescriptorProto, index int) {
servName := serviceName(service)
t.sectionComment(servName + ` Interface`)
t.generateTwirpInterface(file, service)
t.sectionComment(servName + ` Protobuf Client`)
t.generateProtobufClient(file, service)
t.sectionComment(servName + ` JSON Client`)
t.generateJSONClient(file, service)
// Server
t.sectionComment(servName + ` Server Handler`)
t.generateServer(file, service)
}
func (t *twirp) generateTwirpInterface(file *descriptor.FileDescriptorProto, service *descriptor.ServiceDescriptorProto) {
servName := serviceName(service)
comments, err := t.reg.ServiceComments(file, service)
if err == nil {
t.printComments(comments)
}
t.P(`type `, servName, ` interface {`)
for _, method := range service.Method {
comments, err = t.reg.MethodComments(file, service, method)
if err == nil {
t.printComments(comments)
}
t.P(t.generateSignature(method))
t.P()
}
t.P(`}`)
}
func (t *twirp) generateSignature(method *descriptor.MethodDescriptorProto) string {
methName := methodName(method)
inputType := t.goTypeName(method.GetInputType())
outputType := t.goTypeName(method.GetOutputType())
return fmt.Sprintf(` %s(%s.Context, *%s) (*%s, error)`, methName, t.pkgs["context"], inputType, outputType)
}
func (t *twirp) generateJSONClient(file *descriptor.FileDescriptorProto, service *descriptor.ServiceDescriptorProto) {
servName := serviceName(service)
pathPrefixConst := servName + "PathPrefix"
structName := unexported(servName) + "JSONClient"
newJSONClientFunc := "New" + servName + "JSONClient"
methCnt := strconv.Itoa(len(service.Method))
t.P(`type `, structName, ` struct {`)
t.P(` client HTTPClient`)
t.P(` urls [`, methCnt, `]string`)
t.P(`}`)
t.P()
t.P(`// `, newJSONClientFunc, ` creates a JSON client that implements the `, servName, ` interface.`)
t.P(`// It communicates using JSON requests and responses instead of protobuf messages.`)
t.P(`func `, newJSONClientFunc, `(addr string, client HTTPClient) `, servName, ` {`)
t.P(` prefix := urlBase(addr) + `, pathPrefixConst)
t.P(` urls := [`, methCnt, `]string{`)
for _, method := range service.Method {
t.P(` prefix + "`, methodName(method), `",`)
}
t.P(` }`)
t.P(` if httpClient, ok := client.(*`, t.pkgs["http"], `.Client); ok {`)
t.P(` return &`, structName, `{`)
t.P(` client: withoutRedirects(httpClient),`)
t.P(` urls: urls,`)
t.P(` }`)
t.P(` }`)
t.P(` return &`, structName, `{`)
t.P(` client: client,`)
t.P(` urls: urls,`)
t.P(` }`)
t.P(`}`)
t.P()
for i, method := range service.Method {
methName := methodName(method)
inputType := t.goTypeName(method.GetInputType())
outputType := t.goTypeName(method.GetOutputType())
t.P(`func (c *`, structName, `) `, methName, `(ctx `, t.pkgs["context"], `.Context, in *`, inputType, `) (*`, outputType, `, error) {`)
t.P(` out := new(`, outputType, `)`)
t.P(` err := doJSONRequest(ctx, c.client, c.urls[`, strconv.Itoa(i), `], in, out)`)
t.P(` return out, err`)
t.P(`}`)
t.P()
}
}
func (t *twirp) generateProtobufClient(file *descriptor.FileDescriptorProto, service *descriptor.ServiceDescriptorProto) {
servName := serviceName(service)
pathPrefixConst := servName + "PathPrefix"
structName := unexported(servName) + "ProtobufClient"
newProtobufClientFunc := "New" + servName + "ProtobufClient"
methCnt := strconv.Itoa(len(service.Method))
t.P(`type `, structName, ` struct {`)
t.P(` client HTTPClient`)
t.P(` urls [`, methCnt, `]string`)
t.P(`}`)
t.P()
t.P(`// `, newProtobufClientFunc, ` creates a Protobuf client that implements the `, servName, ` interface.`)
t.P(`// It communicates using protobuf messages and can be configured with a custom http.Client.`)
t.P(`func `, newProtobufClientFunc, `(addr string, client HTTPClient) `, servName, ` {`)
t.P(` prefix := urlBase(addr) + `, pathPrefixConst)
t.P(` urls := [`, methCnt, `]string{`)
for _, method := range service.Method {
t.P(` prefix + "`, methodName(method), `",`)
}
t.P(` }`)
t.P(` if httpClient, ok := client.(*`, t.pkgs["http"], `.Client); ok {`)
t.P(` return &`, structName, `{`)
t.P(` client: withoutRedirects(httpClient),`)
t.P(` urls: urls,`)
t.P(` }`)
t.P(` }`)
t.P(` return &`, structName, `{`)
t.P(` client: client,`)
t.P(` urls: urls,`)
t.P(` }`)
t.P(`}`)
t.P()
for i, method := range service.Method {
methName := methodName(method)
inputType := t.goTypeName(method.GetInputType())
outputType := t.goTypeName(method.GetOutputType())
t.P(`func (c *`, structName, `) `, methName, `(ctx `, t.pkgs["context"], `.Context, in *`, inputType, `) (*`, outputType, `, error) {`)
t.P(` out := new(`, outputType, `)`)
t.P(` err := doProtoRequest(ctx, c.client, c.urls[`, strconv.Itoa(i), `], in, out)`)
t.P(` return out, err`)
t.P(`}`)
t.P()
}
}
func (t *twirp) generateServer(file *descriptor.FileDescriptorProto, service *descriptor.ServiceDescriptorProto) {
servName := serviceName(service)
// Server implementation.
servStruct := serviceStruct(service)
t.P(`type `, servStruct, ` struct {`)
t.P(` `, servName)
t.P(` hooks *`, t.pkgs["twirp"], `.ServerHooks`)
t.P(`}`)
t.P()
// Constructor for server implementation
t.P(`func New`, servName, `Server(svc `, servName, `, hooks *`, t.pkgs["twirp"], `.ServerHooks) TwirpServer {`)
t.P(` return &`, servStruct, `{`)
t.P(` `, servName, `: svc,`)
t.P(` hooks: hooks,`)
t.P(` }`)
t.P(`}`)
t.P()
// Write Errors
t.P(`// writeError writes an HTTP response with a valid Twirp error format, and triggers hooks.`)
t.P(`// If err is not a twirp.Error, it will get wrapped with twirp.InternalErrorWith(err)`)
t.P(`func (s *`, servStruct, `) writeError(ctx `, t.pkgs["context"], `.Context, resp `, t.pkgs["http"], `.ResponseWriter, err error) {`)
t.P(` writeError(ctx, resp, err, s.hooks)`)
t.P(`}`)
t.P()
// Routing.
t.generateServerRouting(servStruct, file, service)
// Methods.
for _, method := range service.Method {
t.generateServerMethod(service, method)
}
t.generateServiceMetadataAccessors(file, service)
}
// pathPrefix returns the base path for all methods handled by a particular
// service. It includes a trailing slash. (for example
// "/twirp/twitch.example.Haberdasher/").
func pathPrefix(file *descriptor.FileDescriptorProto, service *descriptor.ServiceDescriptorProto) string {
return fmt.Sprintf("/twirp/%s/", fullServiceName(file, service))
}
// pathFor returns the complete path for requests to a particular method on a
// particular service.
func pathFor(file *descriptor.FileDescriptorProto, service *descriptor.ServiceDescriptorProto, method *descriptor.MethodDescriptorProto) string {
return pathPrefix(file, service) + stringutils.CamelCase(method.GetName())
}
func (t *twirp) generateServerRouting(servStruct string, file *descriptor.FileDescriptorProto, service *descriptor.ServiceDescriptorProto) {
pkgName := pkgName(file)
servName := serviceName(service)
pathPrefixConst := servName + "PathPrefix"
t.P(`// `, pathPrefixConst, ` is used for all URL paths on a twirp `, servName, ` server.`)
t.P(`// Requests are always: POST `, pathPrefixConst, `/method`)
t.P(`// It can be used in an HTTP mux to route twirp requests along with non-twirp requests on other routes.`)
t.P(`const `, pathPrefixConst, ` = `, strconv.Quote(pathPrefix(file, service)))
t.P()
t.P(`func (s *`, servStruct, `) ServeHTTP(resp `, t.pkgs["http"], `.ResponseWriter, req *`, t.pkgs["http"], `.Request) {`)
t.P(` ctx := req.Context()`)
t.P(` ctx = `, t.pkgs["ctxsetters"], `.WithPackageName(ctx, "`, pkgName, `")`)
t.P(` ctx = `, t.pkgs["ctxsetters"], `.WithServiceName(ctx, "`, servName, `")`)
t.P(` ctx = `, t.pkgs["ctxsetters"], `.WithResponseWriter(ctx, resp)`)
t.P()
t.P(` var err error`)
t.P(` ctx, err = callRequestReceived(ctx, s.hooks)`)
t.P(` if err != nil {`)
t.P(` s.writeError(ctx, resp, err)`)
t.P(` return`)
t.P(` }`)
t.P()
t.P(` if req.Method != "POST" {`)
t.P(` msg := `, t.pkgs["fmt"], `.Sprintf("unsupported method %q (only POST is allowed)", req.Method)`)
t.P(` err = badRouteError(msg, req.Method, req.URL.Path)`)
t.P(` s.writeError(ctx, resp, err)`)
t.P(` return`)
t.P(` }`)
t.P()
t.P(` switch req.URL.Path {`)
for _, method := range service.Method {
path := pathFor(file, service, method)
methName := "serve" + stringutils.CamelCase(method.GetName())
t.P(` case `, strconv.Quote(path), `:`)
t.P(` s.`, methName, `(ctx, resp, req)`)
t.P(` return`)
}
t.P(` default:`)
t.P(` msg := `, t.pkgs["fmt"], `.Sprintf("no handler for path %q", req.URL.Path)`)
t.P(` err = badRouteError(msg, req.Method, req.URL.Path)`)
t.P(` s.writeError(ctx, resp, err)`)
t.P(` return`)
t.P(` }`)
t.P(`}`)
t.P()
}
func (t *twirp) generateServerMethod(service *descriptor.ServiceDescriptorProto, method *descriptor.MethodDescriptorProto) {
methName := stringutils.CamelCase(method.GetName())
servStruct := serviceStruct(service)
t.P(`func (s *`, servStruct, `) serve`, methName, `(ctx `, t.pkgs["context"], `.Context, resp `, t.pkgs["http"], `.ResponseWriter, req *`, t.pkgs["http"], `.Request) {`)
t.P(` switch req.Header.Get("Content-Type") {`)
t.P(` case "application/json":`)
t.P(` s.serve`, methName, `JSON(ctx, resp, req)`)
t.P(` case "application/protobuf":`)
t.P(` s.serve`, methName, `Protobuf(ctx, resp, req)`)
t.P(` default:`)
t.P(` msg := `, t.pkgs["fmt"], `.Sprintf("unexpected Content-Type: %q", req.Header.Get("Content-Type"))`)
t.P(` twerr := badRouteError(msg, req.Method, req.URL.Path)`)
t.P(` s.writeError(ctx, resp, twerr)`)
t.P(` }`)
t.P(`}`)
t.P()
t.generateServerJSONMethod(service, method)
t.generateServerProtobufMethod(service, method)
}
func (t *twirp) generateServerJSONMethod(service *descriptor.ServiceDescriptorProto, method *descriptor.MethodDescriptorProto) {
servStruct := serviceStruct(service)
methName := stringutils.CamelCase(method.GetName())
t.P(`func (s *`, servStruct, `) serve`, methName, `JSON(ctx `, t.pkgs["context"], `.Context, resp `, t.pkgs["http"], `.ResponseWriter, req *`, t.pkgs["http"], `.Request) {`)
t.P(` var err error`)
t.P(` ctx = `, t.pkgs["ctxsetters"], `.WithMethodName(ctx, "`, methName, `")`)
t.P(` ctx, err = callRequestRouted(ctx, s.hooks)`)
t.P(` if err != nil {`)
t.P(` s.writeError(ctx, resp, err)`)
t.P(` return`)
t.P(` }`)
t.P()