Prevent duplicate data if snippet is inserted twice

JavaScript/JavaScriptSDK.Tests/E2ETests/PostBuild.ps1

@@ -35,7 +35,7 @@ $content | out-file "$($projectDir)\E2ETests\ai.js"
 $aiPath = "ai.js"
 
 # test the queue
-$queueTest = "var i = 100; while(i--){appInsights.queue.push(function() {window.queueTest('from the queue')})};"
+$queueTest = "var i = 100; while(i--){appInsights.queue && appInsights.queue.push(function() {window.queueTest('from the queue')})};"
 
 # copy snippet and convert protocol to file://
 $snippetLatest = gc "$($projectDir)\..\JavaScriptSDK\snippet.js"

JavaScript/JavaScriptSDK.Tests/E2ETests/snippet.tests.ts

@@ -13,9 +13,11 @@ class SnippetTests extends TestClass {
     private queueCallCount = 100;
     private senderMocks;
 
-    private loadSnippet(path) {
+    private loadSnippet(path, resetWindow = true) {
         // load ai via the snippet
-        window[this.aiName] = undefined;
+        if (resetWindow) {
+            window[this.aiName] = undefined;
+        }
         var key = "E2ETests";
         var snippetPath = window.location.href.split(key)[0] + key + path;
         var scriptElement = document.createElement("script");
@@ -144,6 +146,24 @@ class SnippetTests extends TestClass {
                     Assert.equal("upps!", (<any>data.data).baseData.exceptions[0].message, "error has correct message");
                 })
         });
+
+        var trackPageSpy: SinonSpy;
+
+        this.testCaseAsync({
+            name: "SnippetTests: it's safe to initialize the snippet twice, but it should report only one pageView",
+            stepDelay: 250,
+            steps: [
+                () => {
+                    this.loadSnippet(snippet_Latest);
+                },
+                () => {
+                    trackPageSpy = this.sandbox.spy(window["appInsights"], "trackPageView");
+                    this.loadSnippet(snippet_Latest, false);
+                },
+                () => {
+                    Assert.equal(trackPageSpy.callCount, 0);
+                }]
+        });
     }
 
     private testSnippet(snippetPath) {

JavaScript/JavaScriptSDK/snippet.js

@@ -78,4 +78,8 @@
 
 // global instance must be set in this order to mitigate issues in ie8 and lower
 window.appInsights = appInsights;
-appInsights.trackPageView();
+
+// if somebody calls the snippet twice, don't report page view again
+if (appInsights.queue && appInsights.queue.length === 0) {
+    appInsights.trackPageView();
+}