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

src/cmd/godoc/godoc.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.
 
 package main
 
 import (
         "bytes"
         "encoding/json"
         "flag"
@@ skipping 44 matching lines @@
 
         // file system roots
         // TODO(gri) consider the invariant that goroot always end in '/'
         goroot  = flag.String("goroot", runtime.GOROOT(), "Go root directory")
         testDir = flag.String("testdir", "", "Go root subdirectory - for testing only (faster startups)")
 
         // layout control
         tabwidth       = flag.Int("tabwidth", 4, "tab width")
         showTimestamps = flag.Bool("timestamps", false, "show timestamps with directory listings")
         templateDir    = flag.String("templates", "", "directory containing alternate template files")
+        showPlayground = flag.Bool("play", false, "enable playground in web interface")
 
         // search index
         indexEnabled = flag.Bool("index", false, "enable search index")
         indexFiles   = flag.String("index_files", "", "glob pattern specifying index files;"+
                 "if not empty, the index is read from these files in sorted order")
         maxResults    = flag.Int("maxresults", 10000, "maximum number of full text search results shown")
         indexThrottle = flag.Float64("index_throttle", 0.75, "index throttle value; 0.0 = no time allocated, 1.0 = full throttle")
 
         // file system information
         fsTree      RWValue // *Directory tree of packages, updated with each sync (but sync code is removed now)
@@ skipping 272 matching lines @@
                         code = strings.Replace(code, "\n    ", "\n", -1)
                         // remove output comment
                         if loc := exampleOutputRx.FindStringIndex(code); loc != nil {
                                 code = strings.TrimSpace(code[:loc[0]])
                         }
                 }
 
                 // Write out the playground code in standard Go style
                 // (use tabs, no comment highlight, etc).
                 play := ""
-                if eg.Play != nil {
-                        buf := new(bytes.Buffer)
-                        err := (&printer.Config{Mode: printer.TabIndent, Tabwidth: 8}).Fprint(buf, fset, eg.Play)
+                if eg.Play != nil && *showPlayground {
+                        var buf bytes.Buffer
+                        err := (&printer.Config{Mode: printer.TabIndent, Tabwidth: 8}).Fprint(&buf, fset, eg.Play)
                         if err != nil {
                                 log.Print(err)
                         } else {
                                 play = buf.String()
                         }
                 }
 
                 // Drop output, as the output comment will appear in the code.
                 if wholeFile && play == "" {
                         out = ""
@@ skipping 1048 matching lines @@
                         updateIndex()
                 }
                 delay := 60 * time.Second // by default, try every 60s
                 if *testDir != "" {
                         // in test mode, try once a second for fast startup
                         delay = 1 * time.Second
                 }
                 time.Sleep(delay)
         }
 }