Auto merge of #108934 - matthiaskrgr:rollup-vm414p5, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #106915 (Only load one CSS theme by default)
 - #108294 (Place binder correctly for arbitrary trait bound suggestion)
 - #108778 (x fmt: Don't print all modified files if there's more than 10)
 - #108854 (feat/refactor: improve errors in case of ident with number at start)
 - #108870 (Fix invalid inlining of reexport of reexport of private item)
 - #108917 (Consider target_family as pal)
 - #108922 (Add auto notification for changes to stable mir)
 - #108929 (Fix typo in span_map.rs)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

2 files changed, 53 insertions, 33 deletions

diff --git a/src/librustdoc/html/static/js/main.js b/src/librustdoc/html/static/js/main.js
index 5e8c0e8d10c..403b5004d65 100644
--- a/src/librustdoc/html/static/js/main.js
+++ b/src/librustdoc/html/static/js/main.js
@@ -1,20 +1,9 @@
 // Local js definitions:
 /* global addClass, getSettingValue, hasClass, searchState */
-/* global onEach, onEachLazy, removeClass */
+/* global onEach, onEachLazy, removeClass, getVar */
 
 "use strict";
 
-// Get a value from the rustdoc-vars div, which is used to convey data from
-// Rust to the JS. If there is no such element, return null.
-function getVar(name) {
-    const el = document.getElementById("rustdoc-vars");
-    if (el) {
-        return el.attributes["data-" + name].value;
-    } else {
-        return null;
-    }
-}
-
 // Given a basename (e.g. "storage") and an extension (e.g. ".js"), return a URL
 // for a resource under the root-path, with the resource-suffix.
 function resourcePath(basename, extension) {
@@ -187,6 +176,15 @@ function loadCss(cssUrl) {
     document.getElementsByTagName("head")[0].appendChild(link);
 }
 
+function preLoadCss(cssUrl) {
+    // https://developer.mozilla.org/en-US/docs/Web/HTML/Link_types/preload
+    const link = document.createElement("link");
+    link.href = cssUrl;
+    link.rel = "preload";
+    link.as = "style";
+    document.getElementsByTagName("head")[0].appendChild(link);
+}
+
 (function() {
     const isHelpPage = window.location.pathname.endsWith("/help.html");
 
@@ -207,6 +205,23 @@ function loadCss(cssUrl) {
         // hopefully be loaded when the JS will generate the settings content.
         loadCss(getVar("static-root-path") + getVar("settings-css"));
         loadScript(getVar("static-root-path") + getVar("settings-js"));
+        preLoadCss(getVar("static-root-path") + getVar("theme-light-css"));
+        preLoadCss(getVar("static-root-path") + getVar("theme-dark-css"));
+        preLoadCss(getVar("static-root-path") + getVar("theme-ayu-css"));
+        // Pre-load all theme CSS files, so that switching feels seamless.
+        //
+        // When loading settings.html as a standalone page, the equivalent HTML is
+        // generated in context.rs.
+        setTimeout(() => {
+            const themes = getVar("themes").split(",");
+            for (const theme of themes) {
+                // if there are no themes, do nothing
+                // "".split(",") == [""]
+                if (theme !== "") {
+                    preLoadCss(getVar("root-path") + theme + ".css");
+                }
+            }
+        }, 0);
     };
 
     window.searchState = {
diff --git a/src/librustdoc/html/static/js/storage.js b/src/librustdoc/html/static/js/storage.js
index c72ac254fc0..c3fed9a72d4 100644
--- a/src/librustdoc/html/static/js/storage.js
+++ b/src/librustdoc/html/static/js/storage.js
@@ -7,7 +7,6 @@
 
 const darkThemes = ["dark", "ayu"];
 window.currentTheme = document.getElementById("themeStyle");
-window.mainTheme = document.getElementById("mainThemeStyle");
 
 // WARNING: RUSTDOC_MOBILE_BREAKPOINT MEDIA QUERY
 // If you update this line, then you also need to update the media query with the same
@@ -44,8 +43,6 @@ function getSettingValue(settingName) {
 
 const localStoredTheme = getSettingValue("theme");
 
-const savedHref = [];
-
 // eslint-disable-next-line no-unused-vars
 function hasClass(elem, className) {
     return elem && elem.classList && elem.classList.contains(className);
@@ -102,6 +99,7 @@ function onEach(arr, func, reversed) {
  * @param {function(?)}                   func       - The callback
  * @param {boolean}                       [reversed] - Whether to iterate in reverse
  */
+// eslint-disable-next-line no-unused-vars
 function onEachLazy(lazyArray, func, reversed) {
     return onEach(
         Array.prototype.slice.call(lazyArray),
@@ -125,30 +123,37 @@ function getCurrentValue(name) {
     }
 }
 
-function switchTheme(styleElem, mainStyleElem, newThemeName, saveTheme) {
+// Get a value from the rustdoc-vars div, which is used to convey data from
+// Rust to the JS. If there is no such element, return null.
+const getVar = (function getVar(name) {
+    const el = document.getElementById("rustdoc-vars");
+    if (el) {
+        return el.attributes["data-" + name].value;
+    } else {
+        return null;
+    }
+});
+
+function switchTheme(newThemeName, saveTheme) {
     // If this new value comes from a system setting or from the previously
     // saved theme, no need to save it.
     if (saveTheme) {
         updateLocalStorage("theme", newThemeName);
     }
 
-    if (savedHref.length === 0) {
-        onEachLazy(document.getElementsByTagName("link"), el => {
-            savedHref.push(el.href);
-        });
+    let newHref;
+
+    if (newThemeName === "light" || newThemeName === "dark" || newThemeName === "ayu") {
+        newHref = getVar("static-root-path") + getVar("theme-" + newThemeName + "-css");
+    } else {
+        newHref = getVar("root-path") + newThemeName + getVar("resource-suffix") + ".css";
     }
-    const newHref = savedHref.find(url => {
-        const m = url.match(/static\.files\/(.*)-[a-f0-9]{16}\.css$/);
-        if (m && m[1] === newThemeName) {
-            return true;
-        }
-        const m2 = url.match(/\/([^/]*)\.css$/);
-        if (m2 && m2[1].startsWith(newThemeName)) {
-            return true;
-        }
-    });
-    if (newHref && newHref !== styleElem.href) {
-        styleElem.href = newHref;
+
+    if (!window.currentTheme) {
+        document.write(`<link rel="stylesheet" id="themeStyle" href="${newHref}">`);
+        window.currentTheme = document.getElementById("themeStyle");
+    } else if (newHref !== window.currentTheme.href) {
+        window.currentTheme.href = newHref;
     }
 }
 
@@ -164,7 +169,7 @@ const updateTheme = (function() {
      */
     function updateTheme() {
         const use = (theme, saveTheme) => {
-            switchTheme(window.currentTheme, window.mainTheme, theme, saveTheme);
+            switchTheme(theme, saveTheme);
         };
 
         // maybe the user has disabled the setting in the meantime!