Match the updated specification

https://html.spec.whatwg.org/multipage/scripting.html#valid-custom-element-name

See WICG/webcomponents#239 for background.

index.js

@@ -1,6 +1,7 @@
 'use strict';
-var ncname = require('ncname');
+var isPotentialCustomElementName = require('is-potential-custom-element-name');
 
+// https://html.spec.whatwg.org/multipage/scripting.html#valid-custom-element-name
 var reservedNames = [
 	'annotation-xml',
 	'color-profile',
@@ -33,13 +34,13 @@ function hasError(name) {
 		return 'Custom element names must not start with a hyphen.';
 	}
 
-	// http://www.w3.org/TR/custom-elements/#concepts
-	if (!ncname.test(name)) {
+	// https://html.spec.whatwg.org/multipage/scripting.html#prod-potentialcustomelementname
+	if (!isPotentialCustomElementName(name)) {
 		return 'Invalid element name.';
 	}
 
 	if (reservedNames.indexOf(name) !== -1) {
-		return 'The supplied element name is reserved and can\'t be used.\nSee: http://www.w3.org/TR/custom-elements/#concepts';
+		return 'The supplied element name is reserved and can\'t be used.\nSee: https://html.spec.whatwg.org/multipage/scripting.html#valid-custom-element-name';
 	}
 }
 

package.json

@@ -41,9 +41,9 @@
     "components"
   ],
   "dependencies": {
+    "is-potential-custom-element-name": "^1.0.0",
     "log-symbols": "^1.0.0",
-    "meow": "^3.3.0",
-    "ncname": "^1.0.0"
+    "meow": "^3.3.0"
   },
   "devDependencies": {
     "mocha": "*"

test.js

@@ -35,12 +35,13 @@ it('should return true for `isValid` with warnings for not recommended names', f
 	assert(validate('uni--corn').message);
 	assert(validate('uni-----corn').message);
 	assert(validate('uni-co___rn').message);
-	assert(validate('øl-unicorn').isValid);
+	assert(!validate('øl-unicorn').isValid);
 	assert(validate('øl-unicorn').message);
 	assert(validate('uni-co.rn').isValid);
 	assert(validate('uni-co.rn').message);
 	assert(validate('uni-corné').isValid);
 	assert(validate('uni-corné').message);
 	assert(validate('xml-unicorn').isValid);
 	assert(validate('xml-unicorn').message);
+	assert(validate('foo-💩').message);
 });