fix: wrap unknown args in quotes

lib/validation.ts

@@ -205,7 +205,7 @@ export function validation(
           'Unknown argument: %s',
           'Unknown arguments: %s',
           unknown.length,
-          unknown.join(', ')
+          unknown.map(s => (s.trim() ? s : `"${s}"`)).join(', ')
         )
       );
     }

test/usage.cjs

@@ -1110,6 +1110,27 @@ describe('usage tests', () => {
       r.should.have.property('exit').and.equal(true);
     });
 
+    // Addresses: https://github.com/yargs/yargs/issues/2033
+    it('should wrap whitespace in quotes if provided as an unknown argument', () => {
+      const r = checkUsage(() => {
+        return yargs(['--opt1=hello', ' ', '--opt2=world'])
+          .command({
+            command: '$0',
+            desc: 'default description',
+            builder: yargs =>
+              yargs
+                .option('opt1', {type: 'string'})
+                .option('opt2', {type: 'string'}),
+            handler: noop,
+          })
+          .strict()
+          .wrap(null)
+          .parse();
+      });
+
+      r.errors.should.match(/Unknown argument: " "/);
+    });
+
     it('should fail given multiple option arguments without corresponding descriptions', () => {
       const r = checkUsage(() => {
         const opts = {