throw error for missing attribute value

src/compiler/parse/errors.ts

@@ -157,6 +157,10 @@ export default {
 		code: 'missing-component-definition',
 		message: '<svelte:component> must have a \'this\' attribute'
 	},
+	missing_attribute_value: {
+		code: 'missing-attribute-value',
+		message: 'Expected value for the attribute'
+	},
 	unclosed_script: {
 		code: 'unclosed-script',
 		message: '<script> must have a closing tag'

src/compiler/parse/state/tag.ts

@@ -454,6 +454,10 @@ function read_attribute_value(parser: Parser) {
 		throw error;
 	}
 
+	if (value.length === 0 && !quote_mark) {
+		parser.error(parser_errors.missing_attribute_value);
+	}
+
 	if (quote_mark) parser.index += 1;
 	return value;
 }

test/parser/samples/attribute-empty-error/error.json

@@ -0,0 +1,10 @@
+{
+  "code": "missing-attribute-value",
+  "message": "Expected value for the attribute",
+  "pos": 12,
+  "start": {
+    "character": 12,
+    "column": 12,
+    "line": 1
+  }
+}

test/parser/samples/attribute-empty-error/input.svelte

@@ -0,0 +1 @@
+<div class= ></div>

test/parser/samples/attribute-empty/input.svelte

@@ -0,0 +1 @@
+<div a="" b={''} c='' d="{''}" ></div>

test/parser/samples/attribute-empty/output.json

@@ -0,0 +1,108 @@
+{
+	"html": {
+		"start": 0,
+		"end": 38,
+		"type": "Fragment",
+		"children": [
+			{
+				"start": 0,
+				"end": 38,
+				"type": "Element",
+				"name": "div",
+				"attributes": [
+					{
+						"start": 5,
+						"end": 9,
+						"type": "Attribute",
+						"name": "a",
+						"value": [
+							{
+								"start": 8,
+								"end": 8,
+								"type": "Text",
+								"raw": "",
+								"data": ""
+							}
+						]
+					},
+					{
+						"start": 10,
+						"end": 16,
+						"type": "Attribute",
+						"name": "b",
+						"value": [
+							{
+								"start": 12,
+								"end": 16,
+								"type": "MustacheTag",
+								"expression": {
+									"type": "Literal",
+									"start": 13,
+									"end": 15,
+									"loc": {
+										"start": {
+											"line": 1,
+											"column": 13
+										},
+										"end": {
+											"line": 1,
+											"column": 15
+										}
+									},
+									"value": "",
+									"raw": "''"
+								}
+							}
+						]
+					},
+					{
+						"start": 17,
+						"end": 21,
+						"type": "Attribute",
+						"name": "c",
+						"value": [
+							{
+								"start": 20,
+								"end": 20,
+								"type": "Text",
+								"raw": "",
+								"data": ""
+							}
+						]
+					},
+					{
+						"start": 22,
+						"end": 30,
+						"type": "Attribute",
+						"name": "d",
+						"value": [
+							{
+								"start": 25,
+								"end": 29,
+								"type": "MustacheTag",
+								"expression": {
+									"type": "Literal",
+									"start": 26,
+									"end": 28,
+									"loc": {
+										"start": {
+											"line": 1,
+											"column": 26
+										},
+										"end": {
+											"line": 1,
+											"column": 28
+										}
+									},
+									"value": "",
+									"raw": "''"
+								}
+							}
+						]
+					}
+				],
+				"children": []
+			}
+		]
+	}
+}