Fix and rewrite markup anchor processing (#29931) (#29946)

Backport #29931 by @lunny

Fix #29877

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
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@ -1,50 +1,68 @@
import {svg} from '../svg.js';
const headingSelector = '.markup h1, .markup h2, .markup h3, .markup h4, .markup h5, .markup h6';
// scroll to anchor while respecting the `user-content` prefix that exists on the target
function scrollToAnchor(hash, initial) {
function scrollToAnchor(encodedId, initial) {
// abort if the browser has already scrolled to another anchor during page load
if (initial && document.querySelector(':target')) return;
if (hash?.length <= 1) return;
const id = decodeURIComponent(hash.substring(1));
const el = document.getElementById(`user-content-${id}`);
if (el) {
el.scrollIntoView();
} else if (id.startsWith('user-content-')) { // compat for links with old 'user-content-' prefixed hashes
if (!encodedId || (initial && document.querySelector(':target'))) return;
const id = decodeURIComponent(encodedId);
let el = document.getElementById(`user-content-${id}`);
// check for matching user-generated `a[name]`
if (!el) {
const nameAnchors = document.getElementsByName(`user-content-${id}`);
if (nameAnchors.length) {
el = nameAnchors[0];
}
}
// compat for links with old 'user-content-' prefixed hashes
if (!el && id.startsWith('user-content-')) {
const el = document.getElementById(id);
if (el) el.scrollIntoView();
}
if (el) {
el.scrollIntoView();
}
}
export function initMarkupAnchors() {
if (!document.querySelector('.markup')) return;
const markupEls = document.querySelectorAll('.markup');
if (!markupEls.length) return;
// create link icons for markup headings, the resulting link href will remove `user-content-`
for (const heading of document.querySelectorAll(headingSelector)) {
const originalId = heading.id.replace(/^user-content-/, '');
const a = document.createElement('a');
a.classList.add('anchor');
a.setAttribute('href', `#${encodeURIComponent(originalId)}`);
a.innerHTML = svg('octicon-link');
a.addEventListener('click', (e) => {
scrollToAnchor(e.currentTarget.getAttribute('href'), false);
});
heading.prepend(a);
}
for (const markupEl of markupEls) {
// create link icons for markup headings, the resulting link href will remove `user-content-`
for (const heading of markupEl.querySelectorAll(`:is(h1, h2, h3, h4, h5, h6`)) {
const originalId = heading.id.replace(/^user-content-/, '');
const a = document.createElement('a');
a.classList.add('anchor');
a.setAttribute('href', `#${encodeURIComponent(originalId)}`);
a.innerHTML = svg('octicon-link');
heading.prepend(a);
}
// handle user-defined `name` anchors like `[Link](#link)` linking to `<a name="link"></a>Link`
for (const a of document.querySelectorAll('.markup a[href^="#"]')) {
const href = a.getAttribute('href');
if (!href.startsWith('#user-content-')) continue;
const originalId = href.replace(/^#user-content-/, '');
a.setAttribute('href', `#${encodeURIComponent(originalId)}`);
if (a.closest('.markup').querySelectorAll(`a[name="${originalId}"]`).length !== 1) {
// remove `user-content-` prefix from links so they don't show in url bar when clicked
for (const a of markupEl.querySelectorAll('a[href^="#"]')) {
const href = a.getAttribute('href');
if (!href.startsWith('#user-content-')) continue;
const originalId = href.replace(/^#user-content-/, '');
a.setAttribute('href', `#${originalId}`);
}
// add `user-content-` prefix to user-generated `a[name]` link targets
// TODO: this prefix should be added in backend instead
for (const a of markupEl.querySelectorAll('a[name]')) {
const name = a.getAttribute('name');
if (!name) continue;
a.setAttribute('name', `user-content-${a.name}`);
}
for (const a of markupEl.querySelectorAll('a[href^="#"]')) {
a.addEventListener('click', (e) => {
scrollToAnchor(e.currentTarget.getAttribute('href'), false);
scrollToAnchor(e.currentTarget.getAttribute('href')?.substring(1), false);
});
}
}
scrollToAnchor(window.location.hash, true);
scrollToAnchor(window.location.hash.substring(1), true);
}