Fix language switcher to handle previews

Author: goanpeca

.gitignore

@@ -145,6 +145,7 @@ doc/source/savefig/
 
 # Web & Translations #
 ##############################
+web/preview/
 web/translations/
 web/pandas/es/
 web/pandas/pt/

web/pandas/static/js/language_switcher.js

@@ -1,4 +1,5 @@
 window.addEventListener("DOMContentLoaded", function() {
+  var absBaseUrl = document.baseURI;
   var baseUrl = location.protocol + "//" + location.hostname
   if (location.port) {
      baseUrl = baseUrl + ":" + location.port
@@ -12,6 +13,15 @@ window.addEventListener("DOMContentLoaded", function() {
         'pt': 'Português'
       }
 
+  // Handle preview URLs on github
+  // If preview URL changes, this regex will need to be updated
+  const re = /preview\/pandas-dev\/pandas\/(?<pr>[0-9]*)\//g;
+  var previewUrl = '';
+  for (const match of absBaseUrl.matchAll(re)) {
+    previewUrl = `/preview/pandas-dev/pandas/${match.groups.pr}`;
+  }
+  var pathName = location.pathname.replace(previewUrl, '')
+
   // Create dropdown menu
   function makeDropdown(options) {
     var dropdown = document.createElement("li");
@@ -41,8 +51,8 @@ window.addEventListener("DOMContentLoaded", function() {
         if (i !== 'en') {
           urlLanguage = '/' + i;
         }
-        var pathName = location.pathname.replace('/' + currentLanguage + '/', '/')
-        var newUrl = baseUrl + urlLanguage + pathName
+        pathName = pathName.replace('/' + currentLanguage + '/', '/')
+        var newUrl = baseUrl + previewUrl + urlLanguage + pathName
         window.location.href = newUrl;
       });
       dropdownMenu.appendChild(dropdownItem);

web/pandas_web.py

@@ -87,10 +87,13 @@ def navbar_add_info(context):
         ``has_subitems`` that tells which one of them every element is. It
         also adds a ``slug`` field to be used as a CSS id.
         """
+        lang = context["selected_language"]
         ignore = context["translations"]["ignore"]
+        default_language = context["translations"]["default_language"]
         for i, item in enumerate(context["navbar"]):
             if item["target"] in ignore:
-                item["target"] = "/" + item["target"]
+                if lang != default_language:
+                    item["target"] = "../" + item["target"]
 
             context["navbar"][i] = dict(
                 item,