code review 6523045: godoc: make examples editable and runnable in playground

src/cmd/godoc/main.go

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // godoc: Go Documentation Server
 
 // Web server tree:
 //
 //      http://godoc/           main landing page
 //      http://godoc/doc/       serve from $GOROOT/doc - spec, mem, etc.
@@ skipping 265 matching lines @@
                                 log.Printf("full text index enabled (maxresults = %d)", *maxResults)
                         default:
                                 log.Print("identifier search index enabled")
                         }
                         fs.Fprint(os.Stderr)
                         handler = loggingHandler(handler)
                 }
 
                 registerPublicHandlers(http.DefaultServeMux)
 
-                // Playground handlers are not available in local godoc.
-                http.HandleFunc("/compile", disabledHandler)
-                http.HandleFunc("/share", disabledHandler)
+                playHandler := disabledHandler
+                if *showPlayground {
+                        playHandler = bounceToPlayground
+                }
+                http.HandleFunc("/compile", playHandler)
+                http.HandleFunc("/share", playHandler)
+                http.HandleFunc("/fmt", playHandler)
 
                 // Initialize default directory tree with corresponding timestamp.
                 // (Do it in a goroutine so that launch is quick.)
                 go initFSTree()
 
                 // Immediately update metadata.
                 updateMetadata()
                 // Periodically refresh metadata.
                 go refreshMetadataLoop()
 
@@ skipping 160 matching lines @@
 // An httpWriter is an http.ResponseWriter writing to a bytes.Buffer.
 type httpWriter struct {
         bytes.Buffer
         h    http.Header
         code int
 }
 
 func (w *httpWriter) Header() http.Header  { return w.h }
 func (w *httpWriter) WriteHeader(code int) { w.code = code }
 
+// bounceToPlayground forwards the request to play.golang.org.
+// TODO(adg): implement this stuff locally.
+func bounceToPlayground(w http.ResponseWriter, req *http.Request) {
+        defer req.Body.Close()
+        req.URL.Scheme = "http"
+        req.URL.Host = "play.golang.org"
+        resp, err := http.Post(req.URL.String(), req.Header.Get("Content-type"), req.Body)
+        if err != nil {
+                http.Error(w, err.Error(), 500)
+                return
+        }
+        w.WriteHeader(resp.StatusCode)
+        io.Copy(w, resp.Body)
+        resp.Body.Close()
+}
+
 // disabledHandler serves a 501 "Not Implemented" response.
 func disabledHandler(w http.ResponseWriter, r *http.Request) {
         w.WriteHeader(http.StatusNotImplemented)
         fmt.Fprint(w, "This functionality is not available via local godoc.")
 }