fix(help): ArgsRequiredElseHelp should ignore defaults

Fixes clap-rs#1264

src/parse/arg_matcher.rs

@@ -101,10 +101,6 @@ impl ArgMatcher {
         self.0.args.contains_key(arg)
     }
 
-    pub(crate) fn is_empty(&self) -> bool {
-        self.0.args.is_empty()
-    }
-
     pub(crate) fn arg_names(&self) -> indexmap::map::Keys<Id, MatchedArg> {
         self.0.args.keys()
     }

src/parse/validator.rs

@@ -54,7 +54,11 @@ impl<'help, 'app, 'parser> Validator<'help, 'app, 'parser> {
             }
         }
 
-        if matcher.is_empty()
+        let num_user_values = matcher
+            .arg_names()
+            .filter(|arg_id| matcher.check_explicit(arg_id, ArgPredicate::IsPresent))
+            .count();
+        if num_user_values == 0
             && matcher.subcommand_name().is_none()
             && self.p.is_set(AS::ArgRequiredElseHelp)
         {

tests/builder/app_settings.rs

@@ -259,6 +259,21 @@ fn arg_required_else_help_over_reqs() {
     );
 }
 
+#[test]
+fn arg_required_else_help_with_default() {
+    let result = App::new("arg_required")
+        .setting(AppSettings::ArgRequiredElseHelp)
+        .arg(arg!(--input <PATH>).required(false).default_value("-"))
+        .try_get_matches_from(vec![""]);
+
+    assert!(result.is_err());
+    let err = result.err().unwrap();
+    assert_eq!(
+        err.kind(),
+        ErrorKind::DisplayHelpOnMissingArgumentOrSubcommand
+    );
+}
+
 #[test]
 fn arg_required_else_help_error_message() {
     let app = App::new("test")