fix: correctly backport `svelte:element` to old AST (#11917)

Both `<svelte:element this="div">` and `<svelte:element this={"div"}>` were backported as `tag: "div"` for the old AST. That's wrong because the latter should result in `tag: { type: 'Literal', .. }`. Fixing this makes all the tests in prettier-plugin-svelte pass with Svelte 5.

Also cleaned up a bit of code in the parser.

.changeset/thin-colts-yawn.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: correctly backport `svelte:element` to old AST

packages/svelte/src/compiler/legacy.js

@@ -478,7 +478,11 @@ export function convert(source, ast) {
 			SvelteElement(node, { visit }) {
 				/** @type {import('estree').Expression | string} */
 				let tag = node.tag;
-				if (tag.type === 'Literal' && typeof tag.value === 'string') {
+				if (
+					tag.type === 'Literal' &&
+					typeof tag.value === 'string' &&
+					source[/** @type {number} */ (node.tag.start) - 1] !== '{'
+				) {
 					tag = tag.value;
 				}
 

packages/svelte/src/compiler/phases/1-parse/index.js

@@ -7,7 +7,6 @@ import full_char_code_at from './utils/full_char_code_at.js';
 import * as e from '../../errors.js';
 import { create_fragment } from './utils/create.js';
 import read_options from './read/options.js';
-import { locator } from '../../state.js';
 
 const regex_position_indicator = / \(\d+:\d+\)$/;
 

packages/svelte/src/compiler/phases/1-parse/state/element.js

@@ -14,7 +14,7 @@ const valid_tag_name = /^\!?[a-zA-Z]{1,}:?[a-zA-Z0-9\-]*/;
 /** Invalid attribute characters if the attribute is not surrounded by quotes */
 const regex_starts_with_invalid_attr_value = /^(\/>|[\s"'=<>`])/;
 
-/** @type {Map<string, import('#compiler').SvelteNode['type']>} */
+/** @type {Map<string, import('#compiler').ElementLike['type']>} */
 const root_only_meta_tags = new Map([
 	['svelte:head', 'SvelteHead'],
 	['svelte:options', 'SvelteOptions'],
@@ -23,7 +23,7 @@ const root_only_meta_tags = new Map([
 	['svelte:body', 'SvelteBody']
 ]);
 
-/** @type {Map<string, import('#compiler').SvelteNode['type']>} */
+/** @type {Map<string, import('#compiler').ElementLike['type']>} */
 const meta_tags = new Map([
 	...root_only_meta_tags,
 	['svelte:element', 'SvelteElement'],
@@ -132,11 +132,10 @@ export default function tag(parser) {
 					: 'RegularElement';
 
 	/** @type {import('#compiler').ElementLike} */
-	// @ts-expect-error TODO can't figure out this error
 	const element =
 		type === 'RegularElement'
 			? {
-					type: /** @type {import('#compiler').ElementLike['type']} */ (type),
+					type: type,
 					start,
 					end: -1,
 					name,
@@ -144,12 +143,14 @@ export default function tag(parser) {
 					fragment: create_fragment(true),
 					metadata: {
 						svg: false,
+						mathml: false,
+						scoped: false,
 						has_spread: false
 					},
 					parent: null
 				}
-			: {
+			: /** @type {import('#compiler').ElementLike} */ ({
-					type: /** @type {import('#compiler').ElementLike['type']} */ (type),
+					type,
 					start,
 					end: -1,
 					name,
@@ -159,7 +160,7 @@ export default function tag(parser) {
 					metadata: {
 						svg: false
 					}
-				};
+				});
 
 	parser.allow_whitespace();
 

packages/svelte/tests/parser-legacy/samples/dynamic-element-string/input.svelte

@@ -1,2 +1,7 @@
+<svelte:element this="div"></svelte:element>
+<!-- prettier-ignore -->
+<svelte:element this='div'></svelte:element>
 <svelte:element this={"div"}></svelte:element>
+<!-- prettier-ignore -->
+<svelte:element this={'div'}></svelte:element>
 <svelte:element this={"div"} class="foo"></svelte:element>

packages/svelte/tests/parser-legacy/samples/dynamic-element-string/output.json

@@ -2,40 +2,164 @@
 	"html": {
 		"type": "Fragment",
 		"start": 0,
-		"end": 105,
+		"end": 292,
 		"children": [
 			{
 				"type": "Element",
 				"name": "svelte:element",
 				"start": 0,
-				"end": 46,
+				"end": 44,
 				"tag": "div",
 				"attributes": [],
 				"children": []
 			},
 			{
 				"type": "Text",
-				"start": 46,
+				"start": 44,
-				"end": 47,
+				"end": 45,
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"type": "Comment",
+				"start": 45,
+				"end": 69,
+				"data": " prettier-ignore ",
+				"ignores": []
+			},
+			{
+				"type": "Text",
+				"start": 69,
+				"end": 70,
 				"raw": "\n",
 				"data": "\n"
 			},
 			{
 				"type": "Element",
 				"name": "svelte:element",
-				"start": 47,
+				"start": 70,
-				"end": 105,
+				"end": 114,
 				"tag": "div",
+				"attributes": [],
+				"children": []
+			},
+			{
+				"type": "Text",
+				"start": 114,
+				"end": 115,
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"type": "Element",
+				"name": "svelte:element",
+				"start": 115,
+				"end": 161,
+				"tag": {
+					"type": "Literal",
+					"start": 137,
+					"end": 142,
+					"loc": {
+						"start": {
+							"line": 4,
+							"column": 22
+						},
+						"end": {
+							"line": 4,
+							"column": 27
+						}
+					},
+					"value": "div",
+					"raw": "\"div\""
+				},
+				"attributes": [],
+				"children": []
+			},
+			{
+				"type": "Text",
+				"start": 161,
+				"end": 162,
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"type": "Comment",
+				"start": 162,
+				"end": 186,
+				"data": " prettier-ignore ",
+				"ignores": []
+			},
+			{
+				"type": "Text",
+				"start": 186,
+				"end": 187,
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"type": "Element",
+				"name": "svelte:element",
+				"start": 187,
+				"end": 233,
+				"tag": {
+					"type": "Literal",
+					"start": 209,
+					"end": 214,
+					"loc": {
+						"start": {
+							"line": 6,
+							"column": 22
+						},
+						"end": {
+							"line": 6,
+							"column": 27
+						}
+					},
+					"value": "div",
+					"raw": "'div'"
+				},
+				"attributes": [],
+				"children": []
+			},
+			{
+				"type": "Text",
+				"start": 233,
+				"end": 234,
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"type": "Element",
+				"name": "svelte:element",
+				"start": 234,
+				"end": 292,
+				"tag": {
+					"type": "Literal",
+					"start": 256,
+					"end": 261,
+					"loc": {
+						"start": {
+							"line": 7,
+							"column": 22
+						},
+						"end": {
+							"line": 7,
+							"column": 27
+						}
+					},
+					"value": "div",
+					"raw": "\"div\""
+				},
 				"attributes": [
 					{
 						"type": "Attribute",
-						"start": 76,
+						"start": 263,
-						"end": 87,
+						"end": 274,
 						"name": "class",
 						"value": [
 							{
-								"start": 83,
+								"start": 270,
-								"end": 86,
+								"end": 273,
 								"type": "Text",
 								"raw": "foo",
 								"data": "foo"