tabindex-no-positive

src/validate/html/a11y.ts

@@ -78,6 +78,14 @@ export default function a11y(
 			validator.warn(`A11y: The scope attribute should only be used with <th> elements`, attribute.start);
 		}
 
+		// tabindex-no-positive
+		if (name === 'tabindex') {
+			const value = getStaticAttributeValue(node, 'tabindex');
+			if (!isNaN(value) && +value > 0) {
+				validator.warn(`A11y: avoid tabindex values above zero`, attribute.start);
+			}
+		}
+
 		attributeMap.set(attribute.name, attribute);
 	});
 

test/validator/samples/a11y-tabindex-no-positive/input.html

@@ -0,0 +1,4 @@
+<div tabindex='-1'/>
+<div tabindex='0'/>
+<div tabindex='1'/>
+<div tabindex='{{foo}}'/>

test/validator/samples/a11y-tabindex-no-positive/warnings.json

@@ -0,0 +1,10 @@
+[
+	{
+		"message": "A11y: avoid tabindex values above zero",
+		"loc": {
+			"line": 3,
+			"column": 5
+		},
+		"pos": 46
+	}
+]