feat: improve ssr html mismatch validation

.changeset/hungry-singers-share.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+feat: improve ssr html mismatch validation

packages/svelte/src/compiler/phases/1-parse/utils/html.js

@@ -1,3 +1,4 @@
+import { interactive_elements } from '../../../../constants.js';
 import entities from './entities.js';
 
 const windows_1252 = [
@@ -121,16 +122,6 @@ function validate_code(code) {
 
 // based on http://developers.whatwg.org/syntax.html#syntax-tag-omission
 
-// while `input` is also an interactive element, it is never moved by the browser, so we don't need to check for it
-export const interactive_elements = new Set([
-	'a',
-	'button',
-	'iframe',
-	'embed',
-	'select',
-	'textarea'
-]);
-
 /** @type {Record<string, Set<string>>} */
 const disallowed_contents = {
 	li: new Set(['li']),
@@ -153,36 +144,6 @@ const disallowed_contents = {
 	th: new Set(['td', 'th', 'tr'])
 };
 
-export const disallowed_parapgraph_contents = [
-	'address',
-	'article',
-	'aside',
-	'blockquote',
-	'details',
-	'div',
-	'dl',
-	'fieldset',
-	'figcapture',
-	'figure',
-	'footer',
-	'form',
-	'h1',
-	'h2',
-	'h3',
-	'h4',
-	'h5',
-	'h6',
-	'header',
-	'hr',
-	'menu',
-	'nav',
-	'ol',
-	'pre',
-	'section',
-	'table',
-	'ul'
-];
-
 for (const interactive_element of interactive_elements) {
 	disallowed_contents[interactive_element] = interactive_elements;
 }

packages/svelte/src/compiler/phases/2-analyze/validation.js

@@ -1,3 +1,8 @@
+import {
+	disallowed_parapgraph_contents,
+	interactive_elements,
+	is_tag_valid_with_parent
+} from '../../../constants.js';
 import { error } from '../../errors.js';
 import {
 	extract_identifiers,
@@ -8,7 +13,6 @@ import {
 } from '../../utils/ast.js';
 import { warn } from '../../warnings.js';
 import fuzzymatch from '../1-parse/utils/fuzzymatch.js';
-import { disallowed_parapgraph_contents, interactive_elements } from '../1-parse/utils/html.js';
 import { binding_properties } from '../bindings.js';
 import { ContentEditableBindings, EventModifiers, SVGElements } from '../constants.js';
 import { is_custom_element_node } from '../nodes.js';
@@ -226,127 +230,6 @@ function validate_slot_attribute(context, attribute) {
 	}
 }
 
-// https://html.spec.whatwg.org/multipage/syntax.html#generate-implied-end-tags
-const implied_end_tags = ['dd', 'dt', 'li', 'option', 'optgroup', 'p', 'rp', 'rt'];
-
-/**
- * @param {string} tag
- * @param {string} parent_tag
- * @returns {boolean}
- */
-function is_tag_valid_with_parent(tag, parent_tag) {
-	// First, let's check if we're in an unusual parsing mode...
-	switch (parent_tag) {
-		// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-inselect
-		case 'select':
-			return tag === 'option' || tag === 'optgroup' || tag === '#text';
-		case 'optgroup':
-			return tag === 'option' || tag === '#text';
-		// Strictly speaking, seeing an <option> doesn't mean we're in a <select>
-		// but
-		case 'option':
-			return tag === '#text';
-		// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-intd
-		// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-incaption
-		// No special behavior since these rules fall back to "in body" mode for
-		// all except special table nodes which cause bad parsing behavior anyway.
-
-		// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-intr
-		case 'tr':
-			return (
-				tag === 'th' || tag === 'td' || tag === 'style' || tag === 'script' || tag === 'template'
-			);
-		// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-intbody
-		case 'tbody':
-		case 'thead':
-		case 'tfoot':
-			return tag === 'tr' || tag === 'style' || tag === 'script' || tag === 'template';
-		// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-incolgroup
-		case 'colgroup':
-			return tag === 'col' || tag === 'template';
-		// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-intable
-		case 'table':
-			return (
-				tag === 'caption' ||
-				tag === 'colgroup' ||
-				tag === 'tbody' ||
-				tag === 'tfoot' ||
-				tag === 'thead' ||
-				tag === 'style' ||
-				tag === 'script' ||
-				tag === 'template'
-			);
-		// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-inhead
-		case 'head':
-			return (
-				tag === 'base' ||
-				tag === 'basefont' ||
-				tag === 'bgsound' ||
-				tag === 'link' ||
-				tag === 'meta' ||
-				tag === 'title' ||
-				tag === 'noscript' ||
-				tag === 'noframes' ||
-				tag === 'style' ||
-				tag === 'script' ||
-				tag === 'template'
-			);
-		// https://html.spec.whatwg.org/multipage/semantics.html#the-html-element
-		case 'html':
-			return tag === 'head' || tag === 'body' || tag === 'frameset';
-		case 'frameset':
-			return tag === 'frame';
-		case '#document':
-			return tag === 'html';
-	}
-
-	// Probably in the "in body" parsing mode, so we outlaw only tag combos
-	// where the parsing rules cause implicit opens or closes to be added.
-	// https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-inbody
-	switch (tag) {
-		case 'h1':
-		case 'h2':
-		case 'h3':
-		case 'h4':
-		case 'h5':
-		case 'h6':
-			return (
-				parent_tag !== 'h1' &&
-				parent_tag !== 'h2' &&
-				parent_tag !== 'h3' &&
-				parent_tag !== 'h4' &&
-				parent_tag !== 'h5' &&
-				parent_tag !== 'h6'
-			);
-
-		case 'rp':
-		case 'rt':
-			return implied_end_tags.indexOf(parent_tag) === -1;
-
-		case 'body':
-		case 'caption':
-		case 'col':
-		case 'colgroup':
-		case 'frameset':
-		case 'frame':
-		case 'head':
-		case 'html':
-		case 'tbody':
-		case 'td':
-		case 'tfoot':
-		case 'th':
-		case 'thead':
-		case 'tr':
-			// These tags are only valid with a few parents that have special child
-			// parsing rules -- if we're down here, then none of those matched and
-			// so we allow it only if we don't know what the parent is, as all other
-			// cases are invalid.
-			return parent_tag == null;
-	}
-
-	return true;
-}
-
 /**
  * @type {import('zimmerframe').Visitors<import('#compiler').SvelteNode, import('./types.js').AnalysisState>}
  */

packages/svelte/src/compiler/phases/3-transform/server/transform-server.js

@@ -1207,6 +1207,12 @@ const template_visitors = {
 			inner_context.visit(node, state);
 		}
 
+		if (context.state.options.dev) {
+			context.state.template.push(
+				t_statement(b.stmt(b.call('$.push_element', b.literal(node.name), b.id('$$payload'))))
+			);
+		}
+
 		process_children(trimmed, node, inner_context);
 
 		if (body_expression !== null) {
@@ -1239,6 +1245,9 @@ const template_visitors = {
 		if (!VoidElements.includes(node.name) && metadata.namespace !== 'foreign') {
 			context.state.template.push(t_string(`</${node.name}>`));
 		}
+		if (context.state.options.dev) {
+			context.state.template.push(t_statement(b.stmt(b.call('$.pop_element'))));
+		}
 	},
 	SvelteElement(node, context) {
 		let tag = /** @type {import('estree').Expression} */ (context.visit(node.tag));
@@ -1281,6 +1290,12 @@ const template_visitors = {
 
 		serialize_element_attributes(node, inner_context);
 
+		if (context.state.options.dev) {
+			context.state.template.push(
+				t_statement(b.stmt(b.call('$.push_element', tag, b.id('$$payload'))))
+			);
+		}
+
 		context.state.template.push(
 			t_statement(
 				b.if(
@@ -1304,6 +1319,9 @@ const template_visitors = {
 			),
 			t_expression(anchor_id)
 		);
+		if (context.state.options.dev) {
+			context.state.template.push(t_statement(b.stmt(b.call('$.pop_element'))));
+		}
 	},
 	EachBlock(node, context) {
 		const state = context.state;