all: set GoogleTagManagerID using environment variable

The Google Tag Manager ID is now set using an environment variable,
instead of hardcoding in our templates. This prevent users from sending
traffic data. to the GTM for pkg.go.dev by default, when they fork the
repository.

Change-Id: I5a1f985db20fd19378612593bde3f640b2b40d09
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/241742
Reviewed-by: Andrew Bonventre <andybons@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>

cmd/frontend/main.go

@@ -107,6 +107,7 @@ func main() {
 		ThirdPartyPath:       *thirdPartyPath,
 		DevMode:              *devMode,
 		AppVersionLabel:      cfg.AppVersionLabel(),
+		GoogleTagManagerID:   cfg.GoogleTagManagerID,
 	})
 	if err != nil {
 		log.Fatalf(ctx, "frontend.NewServer: %v", err)

content/static/html/base.tmpl

@@ -10,6 +10,7 @@
 <meta http-equiv="X-UA-Compatible" content="IE=edge">
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <meta name="Description" content="Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.">
+<meta class="js-gtmID" data-gtmID="{{.GoogleTagManagerID}}">
 <link href="https://fonts.googleapis.com/css?family=Work+Sans:600|Roboto:400,500,700|Source+Code+Pro" rel="stylesheet">
 <link href="/static/css/stylesheet.css?version={{.AppVersionLabel}}" rel="stylesheet">
 {{if (.Experiments.IsActive "sidenav")}}
@@ -194,8 +195,8 @@
 
 {{if not .DevMode}}
 <script async>
-  var gtmURL = "https://www.googletagmanager.com/gtm.js?id=GTM-W8MVQXG";
-  loadScript(gtmURL);
+  const gtmID = document.querySelector('.js-gtmID');
+  loadScript(`https://www.googletagmanager.com/gtm.js?id=${gtmID.dataset.path}`);
 
   f = document.createElement("iframe")
   f.src = gtmURL;

internal/config/config.go

@@ -76,6 +76,10 @@ type Config struct {
 
 	GaeEnv string
 
+	// GoogleTagManagerID is the ID used for GoogleTagManager. It has the
+	// structure GTM-XXXX.
+	GoogleTagManagerID string
+
 	// AppMonitoredResource is the resource for the current GAE app.
 	// See https://cloud.google.com/monitoring/api/resources#tag_gae_app for more
 	// details:
@@ -221,12 +225,13 @@ func Init(ctx context.Context) (_ *Config, err error) {
 		Port:      os.Getenv("PORT"),
 		DebugPort: os.Getenv("DEBUG_PORT"),
 		// Resolve AppEngine identifiers
-		ProjectID:    os.Getenv("GOOGLE_CLOUD_PROJECT"),
-		ServiceID:    os.Getenv("GAE_SERVICE"),
-		VersionID:    os.Getenv("GAE_VERSION"),
-		InstanceID:   os.Getenv("GAE_INSTANCE"),
-		GaeEnv:       os.Getenv("GAE_ENV"),
-		QueueService: GetEnv("GO_DISCOVERY_QUEUE_SERVICE", os.Getenv("GAE_SERVICE")),
+		ProjectID:          os.Getenv("GOOGLE_CLOUD_PROJECT"),
+		ServiceID:          os.Getenv("GAE_SERVICE"),
+		VersionID:          os.Getenv("GAE_VERSION"),
+		InstanceID:         os.Getenv("GAE_INSTANCE"),
+		GaeEnv:             os.Getenv("GAE_ENV"),
+		GoogleTagManagerID: os.Getenv("GO_DISCOVERY_GOOGLE_TAG_MANAGER_ID"),
+		QueueService:       GetEnv("GO_DISCOVERY_QUEUE_SERVICE", os.Getenv("GAE_SERVICE")),
 		// LocationID is essentially hard-coded until we figure out a good way to
 		// determine it programmatically, but we check an environment variable in
 		// case it needs to be overridden.

internal/frontend/server.go

@@ -40,6 +40,7 @@ type Server struct {
 	devMode              bool
 	errorPage            []byte
 	appVersionLabel      string
+	googleTagManagerID   string
 
 	mu        sync.Mutex // Protects all fields below
 	templates map[string]*template.Template
@@ -55,6 +56,7 @@ type ServerConfig struct {
 	ThirdPartyPath       string
 	DevMode              bool
 	AppVersionLabel      string
+	GoogleTagManagerID   string
 }
 
 // NewServer creates a new Server for the given database and template directory.
@@ -76,6 +78,7 @@ func NewServer(scfg ServerConfig) (_ *Server, err error) {
 		templates:            ts,
 		taskIDChangeInterval: scfg.TaskIDChangeInterval,
 		appVersionLabel:      scfg.AppVersionLabel,
+		googleTagManagerID:   scfg.GoogleTagManagerID,
 	}
 	errorPageBytes, err := s.renderErrorPage(context.Background(), http.StatusInternalServerError, "error.tmpl", nil)
 	if err != nil {
@@ -185,12 +188,13 @@ func (s *Server) staticPageHandler(templateName, title string) http.HandlerFunc
 
 // basePage contains fields shared by all pages when rendering templates.
 type basePage struct {
-	HTMLTitle       string
-	Query           string
-	Experiments     *experiment.Set
-	GodocURL        string
-	DevMode         bool
-	AppVersionLabel string
+	HTMLTitle          string
+	Query              string
+	Experiments        *experiment.Set
+	GodocURL           string
+	DevMode            bool
+	AppVersionLabel    string
+	GoogleTagManagerID string
 }
 
 // licensePolicyPage is used to generate the static license policy page.
@@ -215,12 +219,13 @@ func (s *Server) licensePolicyHandler() http.HandlerFunc {
 // newBasePage returns a base page for the given request and title.
 func (s *Server) newBasePage(r *http.Request, title string) basePage {
 	return basePage{
-		HTMLTitle:       title,
-		Query:           searchQuery(r),
-		Experiments:     experiment.FromContext(r.Context()),
-		GodocURL:        middleware.GodocURLPlaceholder,
-		DevMode:         s.devMode,
-		AppVersionLabel: s.appVersionLabel,
+		HTMLTitle:          title,
+		Query:              searchQuery(r),
+		Experiments:        experiment.FromContext(r.Context()),
+		GodocURL:           middleware.GodocURLPlaceholder,
+		DevMode:            s.devMode,
+		AppVersionLabel:    s.appVersionLabel,
+		GoogleTagManagerID: s.googleTagManagerID,
 	}
 }
 

internal/middleware/secureheaders.go

@@ -11,19 +11,19 @@ import (
 )
 
 var scriptHashes = []string{
-	// From content/static/html/pages/base.tmpl
+	// From content/static/html/base.tmpl
+	"'sha256-Ajmr6RIM6VV5w/AraBIyO4/XRyuqJlFVukc7TL6feog='",
 	"'sha256-d6W7MwuGWbguTHRzQhf5QN1jXmNo9Ao218saZkWLWZI='",
-	"'sha256-CCu0fuIQFBHSCEpfR6ZRzzcczJIS/VGMGrez8LR49WY='",
 	"'sha256-qPGTOKPn+niRiNKQIEX0Ktwuj+D+iPQWIxnlhPicw58='",
 	// From content/static/html/pages/details.tmpl
 	"'sha256-s16e7aT7Gsajq5UH1DbaEFEnNx2VjvS5Xixcxwm4+F8='",
+	// From content/static/html/pages/fetch.tmpl
+	"'sha256-1J6DWwTWs/QDZ2+ORDuUQCibmFnXXaNXYOtc0Jk6VU4='",
 	// From content/static/html/pages/pkg_doc.tmpl
 	"'sha256-gBtJYPzfgw/0FIACORDIAD08i5rxTQ5J0rhIU656A2U='",
 	"'sha256-91GG/273d2LdEV//lJMbTodGN501OuKZKYYphui+wDQ='",
 	// From content/static/html/worker/index.tmpl
 	"'sha256-5EpitFYSzGNQNUsqi5gAaLqnI3ZWfcRo/6gLTO0oCoE='",
-	// From content/static/html/pages/fetch.tmpl
-	"'sha256-1J6DWwTWs/QDZ2+ORDuUQCibmFnXXaNXYOtc0Jk6VU4='",
 }
 
 // SecureHeaders adds a content-security-policy and other security-related