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eewing
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/**
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* Map of elements that have certain elements that are not allowed inside them, in the sense that they will auto-close the parent/ancestor element.
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* Theoretically one could take advantage of it but most of the time it will just result in confusing behavior and break when SSR'd.
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* There are more elements that are invalid inside other elements, but they're not auto-closed and so don't break SSR and are therefore not listed here.
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* @type {Record<string, { direct: string[]} | { descendant: string[]; reset_by?: string[] }>}
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*/
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const autoclosing_children = {
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// based on http://developers.whatwg.org/syntax.html#syntax-tag-omission
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li: { direct: ['li'] },
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// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dt#technical_summary
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dt: { descendant: ['dt', 'dd'], reset_by: ['dl'] },
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dd: { descendant: ['dt', 'dd'], reset_by: ['dl'] },
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p: {
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descendant: [
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'address',
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'article',
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'aside',
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'blockquote',
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'div',
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'dl',
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'fieldset',
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'footer',
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'form',
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'h1',
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'h2',
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'h3',
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'h4',
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'h5',
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'h6',
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'header',
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'hgroup',
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'hr',
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'main',
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'menu',
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'nav',
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'ol',
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'p',
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'pre',
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'section',
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'table',
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'ul'
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]
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},
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rt: { descendant: ['rt', 'rp'] },
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rp: { descendant: ['rt', 'rp'] },
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optgroup: { descendant: ['optgroup'] },
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option: { descendant: ['option', 'optgroup'] },
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thead: { direct: ['tbody', 'tfoot'] },
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tbody: { direct: ['tbody', 'tfoot'] },
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tfoot: { direct: ['tbody'] },
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tr: { direct: ['tr', 'tbody'] },
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td: { direct: ['td', 'th', 'tr'] },
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th: { direct: ['td', 'th', 'tr'] }
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};
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/**
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* Returns true if the tag is either the last in the list of siblings and will be autoclosed,
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* or not allowed inside the parent tag such that it will auto-close it. The latter results
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* in the browser repairing the HTML, which will likely result in an error during hydration.
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* @param {string} current
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* @param {string} [next]
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*/
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export function closing_tag_omitted(current, next) {
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const disallowed = autoclosing_children[current];
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if (disallowed) {
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if (
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!next ||
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('direct' in disallowed ? disallowed.direct : disallowed.descendant).includes(next)
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) {
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return true;
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}
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}
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return false;
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}
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/**
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* Map of elements that have certain elements that are not allowed inside them, in the sense that the browser will somehow repair the HTML.
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* There are more elements that are invalid inside other elements, but they're not repaired and so don't break SSR and are therefore not listed here.
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* @type {Record<string, { direct: string[]} | { descendant: string[]; reset_by?: string[]; only?: string[] } | { only: string[] }>}
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*/
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const disallowed_children = {
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...autoclosing_children,
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// Strictly speaking, seeing an <option> doesn't mean we're in a <select>, but we assume it here
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// option or optgroup does not have an `only` restriction because newer browsers support rich HTML content
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// inside option elements. For older browsers, hydration will handle the mismatch.
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form: { descendant: ['form'] },
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a: { descendant: ['a'] },
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button: { descendant: ['button'] },
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h1: { descendant: ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'] },
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h2: { descendant: ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'] },
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h3: { descendant: ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'] },
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h4: { descendant: ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'] },
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h5: { descendant: ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'] },
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h6: { descendant: ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'] },
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// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-intd
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// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-incaption
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// No special behavior since these rules fall back to "in body" mode for
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// all except special table nodes which cause bad parsing behavior anyway.
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// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-intd
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tr: { only: ['th', 'td', 'style', 'script', 'template'] },
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// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-intbody
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tbody: { only: ['tr', 'style', 'script', 'template'] },
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thead: { only: ['tr', 'style', 'script', 'template'] },
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tfoot: { only: ['tr', 'style', 'script', 'template'] },
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// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-incolgroup
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colgroup: { only: ['col', 'template'] },
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// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-intable
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table: {
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only: ['caption', 'colgroup', 'tbody', 'thead', 'tfoot', 'style', 'script', 'template']
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},
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// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-inhead
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head: {
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only: [
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'base',
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'basefont',
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'bgsound',
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'link',
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'meta',
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'title',
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'noscript',
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'noframes',
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'style',
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'script',
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'template'
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]
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},
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// https://html.spec.whatwg.org/multipage/semantics.html#the-html-element
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html: { only: ['head', 'body', 'frameset'] },
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frameset: { only: ['frame'] },
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'#document': { only: ['html'] }
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};
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/**
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* Returns an error message if the tag is not allowed inside the ancestor tag (which is grandparent and above) such that it will result
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* in the browser repairing the HTML, which will likely result in an error during hydration.
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* @param {string} child_tag
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* @param {string[]} ancestors All nodes starting with the parent, up until the ancestor, which means two entries minimum
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* @param {string} [child_loc]
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* @param {string} [ancestor_loc]
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* @returns {string | null}
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*/
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export function is_tag_valid_with_ancestor(child_tag, ancestors, child_loc, ancestor_loc) {
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if (child_tag.includes('-')) return null; // custom elements can be anything
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const ancestor_tag = ancestors[ancestors.length - 1];
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const disallowed = disallowed_children[ancestor_tag];
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if (!disallowed) return null;
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if ('reset_by' in disallowed && disallowed.reset_by) {
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for (let i = ancestors.length - 2; i >= 0; i--) {
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const ancestor = ancestors[i];
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if (ancestor.includes('-')) return null; // custom elements can be anything
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// A reset means that forbidden descendants are allowed again
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if (disallowed.reset_by.includes(ancestors[i])) {
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return null;
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}
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}
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}
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if ('descendant' in disallowed && disallowed.descendant.includes(child_tag)) {
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const child = child_loc ? `\`<${child_tag}>\` (${child_loc})` : `\`<${child_tag}>\``;
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const ancestor = ancestor_loc
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? `\`<${ancestor_tag}>\` (${ancestor_loc})`
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: `\`<${ancestor_tag}>\``;
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return `${child} cannot be a descendant of ${ancestor}`;
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}
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return null;
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}
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/**
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* Returns an error message if the tag is not allowed inside the parent tag such that it will result
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* in the browser repairing the HTML, which will likely result in an error during hydration.
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* @param {string} child_tag
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* @param {string} parent_tag
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* @param {string} [child_loc]
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* @param {string} [parent_loc]
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* @returns {string | null}
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*/
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export function is_tag_valid_with_parent(child_tag, parent_tag, child_loc, parent_loc) {
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if (child_tag.includes('-') || parent_tag?.includes('-')) return null; // custom elements can be anything
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if (parent_tag === 'template') return null; // no errors or warning should be thrown in immediate children of template tags
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const disallowed = disallowed_children[parent_tag];
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const child = child_loc ? `\`<${child_tag}>\` (${child_loc})` : `\`<${child_tag}>\``;
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const parent = parent_loc ? `\`<${parent_tag}>\` (${parent_loc})` : `\`<${parent_tag}>\``;
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if (disallowed) {
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if ('direct' in disallowed && disallowed.direct.includes(child_tag)) {
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return `${child} cannot be a direct child of ${parent}`;
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}
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if ('descendant' in disallowed && disallowed.descendant.includes(child_tag)) {
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return `${child} cannot be a child of ${parent}`;
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}
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if ('only' in disallowed && disallowed.only) {
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if (disallowed.only.includes(child_tag)) {
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return null;
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} else {
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return `${child} cannot be a child of ${parent}. \`<${parent_tag}>\` only allows these children: ${disallowed.only.map((d) => `\`<${d}>\``).join(', ')}`;
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}
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}
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}
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// These tags are only valid with a few parents that have special child
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// parsing rules - if we're down here, then none of those matched and
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// so we allow it only if we don't know what the parent is, as all other
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// cases are invalid (and we only get into this function if we know the parent).
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switch (child_tag) {
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case 'body':
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case 'caption':
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case 'col':
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case 'colgroup':
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case 'frameset':
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case 'frame':
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case 'head':
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case 'html':
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return `${child} cannot be a child of ${parent}`;
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case 'thead':
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case 'tbody':
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case 'tfoot':
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return `${child} must be the child of a \`<table>\`, not a ${parent}`;
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case 'td':
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case 'th':
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return `${child} must be the child of a \`<tr>\`, not a ${parent}`;
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case 'tr':
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return `\`<tr>\` must be the child of a \`<thead>\`, \`<tbody>\`, or \`<tfoot>\`, not a ${parent}`;
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}
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return null;
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}
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