Convert frontend code to typescript (#31559)

None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
61105d0618
because of a deprecation that was not showing before the rename).

`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.

Everything appears to work fine.

web_src/js/modules/tippy.ts

@@ -0,0 +1,197 @@
+import tippy, {followCursor} from 'tippy.js';
+import {isDocumentFragmentOrElementNode} from '../utils/dom.ts';
+import {formatDatetime} from '../utils/time.ts';
+
+const visibleInstances = new Set();
+const arrowSvg = `<svg width="16" height="7"><path d="m0 7 8-7 8 7Z" class="tippy-svg-arrow-outer"/><path d="m0 8 8-7 8 7Z" class="tippy-svg-arrow-inner"/></svg>`;
+
+export function createTippy(target, opts = {}) {
+  // the callback functions should be destructured from opts,
+  // because we should use our own wrapper functions to handle them, do not let the user override them
+  const {onHide, onShow, onDestroy, role, theme, arrow, ...other} = opts;
+
+  const instance = tippy(target, {
+    appendTo: document.body,
+    animation: false,
+    allowHTML: false,
+    hideOnClick: false,
+    interactiveBorder: 20,
+    ignoreAttributes: true,
+    maxWidth: 500, // increase over default 350px
+    onHide: (instance) => {
+      visibleInstances.delete(instance);
+      return onHide?.(instance);
+    },
+    onDestroy: (instance) => {
+      visibleInstances.delete(instance);
+      return onDestroy?.(instance);
+    },
+    onShow: (instance) => {
+      // hide other tooltip instances so only one tooltip shows at a time
+      for (const visibleInstance of visibleInstances) {
+        if (visibleInstance.props.role === 'tooltip') {
+          visibleInstance.hide();
+        }
+      }
+      visibleInstances.add(instance);
+      return onShow?.(instance);
+    },
+    arrow: arrow || (theme === 'bare' ? false : arrowSvg),
+    // HTML role attribute, ideally the default role would be "popover" but it does not exist
+    role: role || 'menu',
+    // CSS theme, either "default", "tooltip", "menu", "box-with-header" or "bare"
+    theme: theme || role || 'default',
+    plugins: [followCursor],
+    ...other,
+  });
+
+  if (role === 'menu') {
+    target.setAttribute('aria-haspopup', 'true');
+  }
+
+  return instance;
+}
+
+/**
+ * Attach a tooltip tippy to the given target element.
+ * If the target element already has a tooltip tippy attached, the tooltip will be updated with the new content.
+ * If the target element has no content, then no tooltip will be attached, and it returns null.
+ *
+ * Note: "tooltip" doesn't equal to "tippy". "tooltip" means a auto-popup content, it just uses tippy as the implementation.
+ *
+ * @param target {HTMLElement}
+ * @param content {null|string}
+ * @returns {null|tippy}
+ */
+function attachTooltip(target, content = null) {
+  switchTitleToTooltip(target);
+
+  content = content ?? target.getAttribute('data-tooltip-content');
+  if (!content) return null;
+
+  // when element has a clipboard target, we update the tooltip after copy
+  // in which case it is undesirable to automatically hide it on click as
+  // it would momentarily flash the tooltip out and in.
+  const hasClipboardTarget = target.hasAttribute('data-clipboard-target');
+  const hideOnClick = !hasClipboardTarget;
+
+  const props = {
+    content,
+    delay: 100,
+    role: 'tooltip',
+    theme: 'tooltip',
+    hideOnClick,
+    placement: target.getAttribute('data-tooltip-placement') || 'top-start',
+    followCursor: target.getAttribute('data-tooltip-follow-cursor') || false,
+    ...(target.getAttribute('data-tooltip-interactive') === 'true' ? {interactive: true, aria: {content: 'describedby', expanded: false}} : {}),
+  };
+
+  if (!target._tippy) {
+    createTippy(target, props);
+  } else {
+    target._tippy.setProps(props);
+  }
+  return target._tippy;
+}
+
+function switchTitleToTooltip(target) {
+  let title = target.getAttribute('title');
+  if (title) {
+    // apply custom formatting to relative-time's tooltips
+    if (target.tagName.toLowerCase() === 'relative-time') {
+      const datetime = target.getAttribute('datetime');
+      if (datetime) {
+        title = formatDatetime(new Date(datetime));
+      }
+    }
+    target.setAttribute('data-tooltip-content', title);
+    target.setAttribute('aria-label', title);
+    // keep the attribute, in case there are some other "[title]" selectors
+    // and to prevent infinite loop with <relative-time> which will re-add
+    // title if it is absent
+    target.setAttribute('title', '');
+  }
+}
+
+/**
+ * Creating tooltip tippy instance is expensive, so we only create it when the user hovers over the element
+ * According to https://www.w3.org/TR/DOM-Level-3-Events/#events-mouseevent-event-order , mouseover event is fired before mouseenter event
+ * Some browsers like PaleMoon don't support "addEventListener('mouseenter', capture)"
+ * The tippy by default uses "mouseenter" event to show, so we use "mouseover" event to switch to tippy
+ * @param e {Event}
+ */
+function lazyTooltipOnMouseHover(e) {
+  e.target.removeEventListener('mouseover', lazyTooltipOnMouseHover, true);
+  attachTooltip(this);
+}
+
+// Activate the tooltip for current element.
+// If the element has no aria-label, use the tooltip content as aria-label.
+function attachLazyTooltip(el) {
+  el.addEventListener('mouseover', lazyTooltipOnMouseHover, {capture: true});
+
+  // meanwhile, if the element has no aria-label, use the tooltip content as aria-label
+  if (!el.hasAttribute('aria-label')) {
+    const content = el.getAttribute('data-tooltip-content');
+    if (content) {
+      el.setAttribute('aria-label', content);
+    }
+  }
+}
+
+// Activate the tooltip for all children elements.
+function attachChildrenLazyTooltip(target) {
+  for (const el of target.querySelectorAll('[data-tooltip-content]')) {
+    attachLazyTooltip(el);
+  }
+}
+
+export function initGlobalTooltips() {
+  // use MutationObserver to detect new "data-tooltip-content" elements added to the DOM, or attributes changed
+  const observerConnect = (observer) => observer.observe(document, {
+    subtree: true,
+    childList: true,
+    attributeFilter: ['data-tooltip-content', 'title'],
+  });
+  const observer = new MutationObserver((mutationList, observer) => {
+    const pending = observer.takeRecords();
+    observer.disconnect();
+    for (const mutation of [...mutationList, ...pending]) {
+      if (mutation.type === 'childList') {
+        // mainly for Vue components and AJAX rendered elements
+        for (const el of mutation.addedNodes) {
+          if (!isDocumentFragmentOrElementNode(el)) continue;
+          attachChildrenLazyTooltip(el);
+          if (el.hasAttribute('data-tooltip-content')) {
+            attachLazyTooltip(el);
+          }
+        }
+      } else if (mutation.type === 'attributes') {
+        attachTooltip(mutation.target);
+      }
+    }
+    observerConnect(observer);
+  });
+  observerConnect(observer);
+
+  attachChildrenLazyTooltip(document.documentElement);
+}
+
+export function showTemporaryTooltip(target, content) {
+  // if the target is inside a dropdown, don't show the tooltip because when the dropdown
+  // closes, the tippy would be pushed unsightly to the top-left of the screen like seen
+  // on the issue comment menu.
+  if (target.closest('.ui.dropdown > .menu')) return;
+
+  const tippy = target._tippy ?? attachTooltip(target, content);
+  tippy.setContent(content);
+  if (!tippy.state.isShown) tippy.show();
+  tippy.setProps({
+    onHidden: (tippy) => {
+      // reset the default tooltip content, if no default, then this temporary tooltip could be destroyed
+      if (!attachTooltip(target)) {
+        tippy.destroy();
+      }
+    },
+  });
+}