A client/server helper wrapper for endpoints in Go.

go/src/infra/gae/epclient/epclient.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.
+
+// The following comment allows `go generate` to correctly generate clients
+// for all endpoints services located in the "infra/gae/epservice" package.
+//go:generate goapp run epclient.go
+
+// EPClient will auto-generate endpoints clients from Google Cloud Endpoint
+// service definitions. The tool assumes that:
+//   * all go endpoint service definitions occur in a package which has
+//     a public method `RegisterEndpointsService(*endpoints.Server) error`, and
+//     that calling this method will register the endpoints service with the
+//     provided server or return an error.
+//   * goapp exists in PATH (and understands all the import paths in the
+//     defined services)
+//   * google-api-go-generator exists in PATH.

[dnj, 2015/06/08 16:43:18]

Could you "enforce" this by adding it as a Go dependency here? If this package
becomes go-gettable, it would be useful to have the API generator be pulled in
as a dependency.

[iannucci, 2015/06/09 00:01:54]

It's a 'main' package, so I can't add it as an import dependency.

+package main
+
+import (
+        "bytes"
+        "encoding/json"
+        "flag"
+        "fmt"
+        "io/ioutil"
+        "os"
+        "os/exec"
+        "path/filepath"
+        "strings"
+        "text/template"
+        "time"
+
+        "infra/libs/jsutil"
+)
+
+var (
+        servicePackagesBase = flag.String("pkgs", "infra/gae/epservice",
+                "The base Go package to walk to find service definitions.")
+        outDir = flag.String("outdir", ".",
+                "The directory to generate the client libraries in.")
+        runOnly = flag.Bool("run", false,
+                "If set to true, will run the server and wait, without generating any clients.")
+        clearDatastore = flag.Bool("clear_datastore", false,
+                "If set to true, will clear the datastore when in 'run' mode.")
+)
+
+var serviceScript = `
+package main

[dnj, 2015/06/08 16:43:18]

Add "generated" comment, info, timestamp.

[iannucci, 2015/06/09 00:01:54]

Done.

+
+import (
+        "fmt"
+
+{{range $idx, $pkg := .Pkgs}}
+        pkg{{$idx}} "{{$pkg.Imp}}"{{end}}
+
+        "github.com/GoogleCloudPlatform/go-endpoints/endpoints"
+)
+
+func init() {
+        var err error
+        server := endpoints.NewServer("")
+
+        {{range $idx, $pkg := .Pkgs }}
+        err = pkg{{$idx}}.RegisterEndpointsService(server)
+        if err != nil {
+                panic(fmt.Errorf("Error while registering service {{$pkg}}: %s", err))
+        }
+        {{end}}
+
+        server.HandleHTTP(nil)
+}
+`
+
+const appYaml = `
+application: epclient-tmp-app

[dnj, 2015/06/08 16:43:18]

Add "generated" comment, info, timestamp.

[iannucci, 2015/06/09 00:01:54]

Done.

+version: nope
+runtime: go
+api_version: go1
+
+handlers:
+- url: /.*
+  script: _go_app
+`
+
+var temp = template.Must(template.New("service").Parse(serviceScript))
+
+// Pkg holds the import and real filesystem paths of an endpoint service
+// package. It's exported merely for reflection purposes, since it's used
+// by text/template.
+type Pkg struct {
+        Imp string
+        Pth string
+}
+
+func boom(err error) {
+        if err != nil {
+                panic(err)
+        }
+}
+
+func getPkgs() []Pkg {
+        cmd := exec.Command("goapp", "list", "-json", filepath.Join(*servicePackagesBase, "..."))
+        d, err := cmd.Output()
+        boom(err)
+
+        d = []byte("[" + strings.Replace(string(d), "}\n{", "},{", -1) + "]")
+
+        js := interface{}(nil)
+        boom(json.Unmarshal(d, &js))
+
+        ret := []Pkg{}
+
+        for _, m := range js.([]interface{}) {
+                ret = append(ret, Pkg{
+                        jsutil.Get(m, "ImportPath").(string),
+                        jsutil.Get(m, "Dir").(string),
+                })
+        }
+
+        return ret
+}
+
+func writeFiles(dir string, pkgs []Pkg) {
+        buf := &bytes.Buffer{}
+        if err := temp.Execute(buf, struct{ Pkgs []Pkg }{pkgs}); err != nil {
+                panic(err)
+        }
+
+        if err := ioutil.WriteFile(filepath.Join(dir, "app.go"), buf.Bytes(), 0666); err != nil {
+                panic(err)
+        }
+
+        if err := ioutil.WriteFile(filepath.Join(dir, "app.yaml"), []byte(appYaml), 0666); err != nil {
+                panic(err)
+        }
+}
+
+func parseFlags() {
+        err := error(nil)

[dnj, 2015/06/08 16:43:17]

I generally prefer "var err error" *shrug* Up to you of course.

[iannucci, 2015/06/09 00:01:53]

me too... I was getting bikeshedding elsewhere on this. changed to the other
thing.

+        flag.Parse()
+        if *outDir == "" {
+                if *outDir, err = os.Getwd(); err != nil {
+                        panic(err)
+                }
+        }
+        if *outDir, err = filepath.Abs(*outDir); err != nil {
+                panic(err)
+        }
+}
+
+func startServer(dir string) (func(), func()) {
+        args := []string{"serve"}
+        if *clearDatastore {
+                args = append(args, "-clear_datastore")
+        }
+        args = append(args, dir)
+        server := exec.Command("goapp", args...)
+        server.Stdout = os.Stdout
+        server.Stderr = os.Stderr
+        if err := server.Start(); err != nil {
+                panic(err)
+        }
+        time.Sleep(time.Second) // yeah yeah, sue me.

[dnj, 2015/06/08 16:43:18]

Since you know the discovery service URL, you could just ping it here until it
succeeds.

[iannucci, 2015/06/09 00:01:54]

Done.

+        fmt.Println("Discovery service up")
+
+        wait := func() { server.Wait() }
+        stop := func() {
+                server.Process.Signal(os.Interrupt)
+                wait()
+        }
+        return stop, wait
+}
+
+func generate() {
+        gencmd := exec.Command("google-api-go-generator", "-discoveryurl", "http://localhost:8080/_ah/api/discovery/v1/apis", "-gendir", *outDir, "-cache=false")
+        gencmd.Stdout = os.Stdout
+        gencmd.Stderr = os.Stderr
+        if err := gencmd.Run(); err != nil {
+                panic(err)
+        }
+}
+
+func main() {
+        parseFlags()
+

[dnj, 2015/06/08 16:43:18]

Test that "google-api-go-generator" and "goapp" are on PATH first.

[iannucci, 2015/06/09 00:01:53]

Done.

+        pkgs := getPkgs()
+
+        dir, err := ioutil.TempDir("", "epclient_gen")
+        if err != nil {
+                panic(err)
+        }
+        defer os.RemoveAll(dir)
+
+        writeFiles(dir, pkgs)
+
+        stop, wait := startServer(dir)
+        defer stop()
+
+        if *runOnly {
+                wait()
+        } else {
+                generate()
+        }
+
+        // inject DoWithRetries methods.
+}