[fix] create AST node of empty string for empty attribute values (#6539)

Co-authored-by: Conduitry <git@chor.date>

src/compiler/parse/state/tag.ts

@@ -422,6 +422,15 @@ function get_directive_type(name: string): DirectiveType {
 
 function read_attribute_value(parser: Parser) {
 	const quote_mark = parser.eat("'") ? "'" : parser.eat('"') ? '"' : null;
+	if (quote_mark && parser.eat(quote_mark)) {
+		return [{
+			start: parser.index - 1,
+			end: parser.index - 1,
+			type: 'Text',
+			raw: '',
+			data: ''
+		}];
+	}
 
 	const regex = (
 		quote_mark === "'" ? /'/ :

test/parser/samples/element-with-attribute-empty-string/input.svelte

@@ -0,0 +1,2 @@
+<span attr=""></span>
+<span attr=''></span>

test/parser/samples/element-with-attribute-empty-string/output.json

@@ -0,0 +1,64 @@
+{
+	"html": {
+		"start": 0,
+		"end": 43,
+		"type": "Fragment",
+		"children": [
+			{
+				"start": 0,
+				"end": 21,
+				"type": "Element",
+				"name": "span",
+				"attributes": [
+					{
+						"start": 6,
+						"end": 13,
+						"type": "Attribute",
+						"name": "attr",
+						"value": [
+							{
+								"start": 12,
+								"end": 12,
+								"type": "Text",
+								"raw": "",
+								"data": ""
+							}
+						]
+					}
+				],
+				"children": []
+			},
+			{
+				"start": 21,
+				"end": 22,
+				"type": "Text",
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"start": 22,
+				"end": 43,
+				"type": "Element",
+				"name": "span",
+				"attributes": [
+					{
+						"start": 28,
+						"end": 35,
+						"type": "Attribute",
+						"name": "attr",
+						"value": [
+							{
+								"start": 34,
+								"end": 34,
+								"type": "Text",
+								"raw": "",
+								"data": ""
+							}
+						]
+					}
+				],
+				"children": []
+			}
+		]
+	}
+}

test/parser/samples/element-with-attribute/input.svelte

@@ -0,0 +1,2 @@
+<span attr="foo"></span>
+<span attr='bar'></span>

test/parser/samples/element-with-attribute/output.json

@@ -0,0 +1,64 @@
+{
+	"html": {
+		"start": 0,
+		"end": 49,
+		"type": "Fragment",
+		"children": [
+			{
+				"start": 0,
+				"end": 24,
+				"type": "Element",
+				"name": "span",
+				"attributes": [
+					{
+						"start": 6,
+						"end": 16,
+						"type": "Attribute",
+						"name": "attr",
+						"value": [
+							{
+								"start": 12,
+								"end": 15,
+								"type": "Text",
+								"raw": "foo",
+								"data": "foo"
+							}
+						]
+					}
+				],
+				"children": []
+			},
+			{
+				"start": 24,
+				"end": 25,
+				"type": "Text",
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"start": 25,
+				"end": 49,
+				"type": "Element",
+				"name": "span",
+				"attributes": [
+					{
+						"start": 31,
+						"end": 41,
+						"type": "Attribute",
+						"name": "attr",
+						"value": [
+							{
+								"start": 37,
+								"end": 40,
+								"type": "Text",
+								"raw": "bar",
+								"data": "bar"
+							}
+						]
+					}
+				],
+				"children": []
+			}
+		]
+	}
+}