chore: consolidate checks for never-static attributes (#14372)

We're using string checks in various places, better to have it encapsulated in one function

Author: dummdidumm

packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js

@@ -1,6 +1,6 @@
 /** @import { AST } from '#compiler' */
 /** @import { Context } from '../types' */
-import { is_mathml, is_svg, is_void } from '../../../../utils.js';
+import { cannot_be_set_statically, is_mathml, is_svg, is_void } from '../../../../utils.js';
 import {
 	is_tag_valid_with_ancestor,
 	is_tag_valid_with_parent
@@ -77,9 +77,7 @@ export function RegularElement(node, context) {
 
 	if (
 		node.attributes.some(
-			(attribute) =>
-				attribute.type === 'Attribute' &&
-				(attribute.name === 'autofocus' || attribute.name === 'muted')
+			(attribute) => attribute.type === 'Attribute' && cannot_be_set_statically(attribute.name)
 		)
 	) {
 		mark_subtree_dynamic(context.path);

packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js

@@ -5,6 +5,7 @@
 /** @import { Scope } from '../../../scope' */
 import { escape_html } from '../../../../../escaping.js';
 import {
+	cannot_be_set_statically,
 	is_boolean_attribute,
 	is_dom_property,
 	is_load_error_element,
@@ -262,8 +263,7 @@ export function RegularElement(node, context) {
 
 			if (
 				!is_custom_element &&
-				attribute.name !== 'autofocus' &&
-				attribute.name !== 'muted' &&
+				!cannot_be_set_statically(attribute.name) &&
 				(attribute.value === true || is_text_attribute(attribute))
 			) {
 				const name = get_attribute_name(node, attribute);

packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/fragment.js

@@ -3,6 +3,7 @@
 /** @import { Scope } from '../../../../scope.js' */
 /** @import { ComponentContext } from '../../types' */
 import { escape_html } from '../../../../../../escaping.js';
+import { cannot_be_set_statically } from '../../../../../../utils.js';
 import { is_event_attribute } from '../../../../../utils/ast.js';
 import * as b from '../../../../../utils/builders.js';
 import { build_template_chunk, build_update } from './utils.js';
@@ -142,7 +143,7 @@ function is_static_element(node) {
 			return false;
 		}
 
-		if (attribute.name === 'autofocus' || attribute.name === 'muted') {
+		if (cannot_be_set_statically(attribute.name)) {
 			return false;
 		}
 

packages/svelte/src/utils.js

@@ -222,6 +222,17 @@ export function is_dom_property(name) {
 	return DOM_PROPERTIES.includes(name);
 }
 
+const NON_STATIC_PROPERTIES = ['autofocus', 'muted'];
+
+/**
+ * Returns `true` if the given attribute cannot be set through the template
+ * string, i.e. needs some kind of JavaScript handling to work.
+ * @param {string} name
+ */
+export function cannot_be_set_statically(name) {
+	return NON_STATIC_PROPERTIES.includes(name);
+}
+
 /**
  * Subset of delegated events which should be passive by default.
  * These two are already passive via browser defaults on window, document and body.