From d83ae60650a8f7ea6e33e19ae6b3b1ad5366de1b Mon Sep 17 00:00:00 2001
From: Justin Van Patten <jvp@justinvp.com>
Date: Thu, 27 Jun 2019 13:20:28 -0700
Subject: [PATCH] Fix bug in lang chooser

If I've previously viewed a page in our docs with the language tabs,
such as the Get Started guide, and I click the Python tab, that language
choice will be persisted to a cookie.

If I then visit our Node.js API docs, the lang chooser will see the
saved value of "Python" and try to select that tab, hiding all other
language snippets. But our Node.js API docs only contain JavaScript and
TypeScript snippets, so the end result is that all snippets are hidden
and no tab is selected.

This change fixes that. If the value in the cookie does not exist in any
of the tabs on the page, fallback to the default (JavaScript), otherwise
fallback to the first tab that is available on the page.
---
 assets/js/langchoose.js | 58 ++++++++++++++++++++++-------------------
 1 file changed, 31 insertions(+), 27 deletions(-)

diff --git a/assets/js/langchoose.js b/assets/js/langchoose.js
index a292a37743f7..2eea21080d3b 100644
--- a/assets/js/langchoose.js
+++ b/assets/js/langchoose.js
@@ -13,18 +13,12 @@ function selectLanguage(lang) {
 
         // Change the active tab.
         var langTabs = 0;
-        $("a").each(function (i, e) {
-            var classes = getElemClasses(e);
-            for (var i = 0; i < classes.length; i++) {
-                if (classes[i] === "langtab") {
-                    langTabs++;
-                    if (e.innerText.toLowerCase() === lang) {
-                        $(e).addClass("is-active");
-                    } else {
-                        $(e).removeClass("is-active");
-                    }
-                    break;
-                }
+        $("a.langtab").each(function (i, e) {
+            langTabs++;
+            if (e.innerText.toLowerCase() === lang) {
+                $(e).addClass("is-active");
+            } else {
+                $(e).removeClass("is-active");
             }
         });
 
@@ -87,26 +81,36 @@ function selectLanguage(lang) {
 // The first time the DOM is finished loading, select the right language.  If no language is set as the preferred
 // language yet, then JavaScript is chosen as the preferred language as a default.
 $(function() {
-    // For every language tab, inject a handler and make the correct one hidden.
-    $("a").each(function (i, e) {
-        var classes = getElemClasses(e);
-        for (var i = 0; i < classes.length; i++) {
-            if (classes[i] === "langtab") {
-                var lang = e.innerText.toLowerCase();
-                e.addEventListener("click", function() {
-                    selectLanguage(lang);
-                });
-                break;
-            }
-        }
+    var tabLangsOnPage = {};
+    $("a.langtab").each(function (i, e) {
+        var lang = e.innerText.toLowerCase();
+
+        // Save the languages we've seen.
+        tabLangsOnPage[lang] = true;
+
+        // For every language tab, inject a handler and make the correct one hidden.
+        e.addEventListener("click", function() {
+            selectLanguage(lang);
+        });
     });
 
-    // Now select the right language based on whether there's a cookie (defaulting to JavaScript).
+    var tabLangsOnPageKeys = Object.keys(tabLangsOnPage);
+
+    // If we didn't find any lang tabs, there's nothing else to do.
+    if (tabLangsOnPageKeys.length === 0) {
+        return;
+    }
+
+    // Now select the right language based on whether there's a cookie, defaulting to JavaScript,
+    // if it's among the tabs, otherwise falling back to the first lang we find.
     var langCookie = decodeURIComponent(
         document.cookie.replace(/(?:(?:^|.*;\s*)pulumi_language\s*\=\s*([^;]*).*$)|^.*$/, "$1"));
-    if (langCookie) {
+
+    if (langCookie && tabLangsOnPage.hasOwnProperty(langCookie)) {
         selectLanguage(langCookie);
-    } else {
+    } else if (tabLangsOnPage.hasOwnProperty("javascript")) {
         selectLanguage("javascript");
+    } else if (tabLangsOnPageKeys.length > 0) {
+        selectLanguage(tabLangsOnPageKeys[0]);
     }
 });