Also get previous "system-preference" setting

Author: GuillaumeGomez

src/librustdoc/html/static/js/settings.js

@@ -2,6 +2,7 @@
 /* global getSettingValue, getVirtualKey, updateLocalStorage, updateSystemTheme */
 /* global addClass, removeClass, onEach, onEachLazy, blurHandler, elemIsInParent */
 /* global MAIN_ID, getVar, getSettingsButton, isUsingSystemTheme, CURRENT_THEME_SETTING_VERSION */
+/* global getTheme, getPreferredDarkTheme, getPreferredLightTheme */
 
 "use strict";
 
@@ -159,19 +160,19 @@
                 "name": "Theme",
                 "js_name": "theme",
                 "js_name_version": CURRENT_THEME_SETTING_VERSION,
-                "default": "system-preference",
+                "default": getTheme(),
                 "options": themes.concat("system preference"),
             },
             {
                 "name": "Preferred light theme",
                 "js_name": "preferred-light-theme",
-                "default": "light",
+                "default": getPreferredLightTheme(),
                 "options": themes,
             },
             {
                 "name": "Preferred dark theme",
                 "js_name": "preferred-dark-theme",
-                "default": "dark",
+                "default": getPreferredDarkTheme(),
                 "options": themes,
             },
             {

src/librustdoc/html/static/js/storage.js

@@ -47,15 +47,34 @@ function isUsingSystemTheme() {
     return current === null || current === "system-preference";
 }
 
+function valueOr(value, or) {
+    if (value !== null) {
+        return value;
+    }
+    return or;
+}
+
 function getTheme() {
     const current = getSettingValue(`theme${CURRENT_THEME_SETTING_VERSION}`);
     if (current === null) {
         // We try to get what's being used in the previous version.
-        return getSettingValue("theme");
+        const isUsingSystemTheme = getSettingValue("use-system-theme");
+        if (isUsingSystemTheme === "true") {
+            return "system-preference";
+        }
+        return valueOr(getSettingValue("theme"), "system-preference");
     }
     return current;
 }
 
+function getPreferredDarkTheme() {
+    return valueOr(getSettingValue("preferred-dark-theme"), "dark");
+}
+
+function getPreferredLightTheme() {
+    return valueOr(getSettingValue("preferred-light-theme"), "light");
+}
+
 const savedHref = [];
 
 // eslint-disable-next-line no-unused-vars
@@ -194,8 +213,8 @@ const updateSystemTheme = (function() {
         };
         // maybe the user has disabled the setting in the meantime!
         if (isUsingSystemTheme()) {
-            const lightTheme = getSettingValue("preferred-light-theme") || "light";
-            const darkTheme = getSettingValue("preferred-dark-theme") || "dark";
+            const lightTheme = getPreferredLightTheme();
+            const darkTheme = getPreferredDarkTheme();
 
             if (mql.matches) {
                 use(darkTheme, false);

src/test/rustdoc-gui/settings.goml

@@ -29,6 +29,16 @@ wait-for-css: ("#settings", {"display": "block"})
 wait-for: "#alternative-display #search"
 assert: "#main-content.hidden"
 
+// Checking the default values of the themes:
+// * default: system
+// * default preferred dark: dark
+// * default preferred light: light
+assert-property: ("#theme-system-preference", {"checked": "true"})
+assert-property: ("#preferred-dark-theme-dark", {"checked": "true"})
+assert-property: ("#preferred-light-theme-light", {"checked": "true"})
+assert: ".setting-line:not(.hidden) #preferred-dark-theme"
+assert: ".setting-line:not(.hidden) #preferred-light-theme"
+
 // Now let's check the content of the settings menu.
 local-storage: {"rustdoc-theme2": "dark"}
 reload: