fix(usage): Remove redundant duplicate parameters when there is a conflict error

src/parse/validator.rs

@@ -285,6 +285,12 @@ impl<'help, 'cmd> Validator<'help, 'cmd> {
         let used_filtered: Vec<Id> = matcher
             .arg_names()
             .filter(|arg_id| matcher.check_explicit(arg_id, ArgPredicate::IsPresent))
+            .filter(|n| {
+                // Filter out the args we don't want to specify.
+                self.cmd
+                    .find(n)
+                    .map_or(true, |a| !a.is_hide_set() && !self.required.contains(&a.id))
+            })
             .filter(|key| !conflicting_keys.contains(key))
             .cloned()
             .collect();

tests/builder/main.rs

@@ -42,6 +42,7 @@ mod tests;
 mod unicode;
 mod unique_args;
 mod utf16;
+mod usage;
 mod utf8;
 mod utils;
 mod validators;

tests/builder/usage.rs

@@ -0,0 +1,37 @@
+use clap::{Arg, Command, ErrorKind};
+
+fn cmd() -> Command<'static> {
+    Command::new("prog")
+        .arg(Arg::new("a").required(true))
+        .arg(Arg::new("b").short('b').takes_value(true).group("debug"))
+        .arg(Arg::new("c").short('c').takes_value(true).group("debug"))
+}
+
+#[test]
+fn valid_cases() {
+    let res = cmd().try_get_matches_from(vec!["prog", "aaa"]);
+    assert!(res.is_ok(), "{}", res.unwrap_err());
+    let res = cmd().try_get_matches_from(vec!["prog", "aaa", "-b", "bbb"]);
+    assert!(res.is_ok(), "{}", res.unwrap_err());
+    let res = cmd().try_get_matches_from(vec!["prog", "aaa", "-c", "ccc"]);
+    assert!(res.is_ok(), "{}", res.unwrap_err());
+}
+
+/// https://github.com/clap-rs/clap/issues/3665 and https://github.com/clap-rs/clap/issues/3556
+#[test]
+fn no_duplicate_required_argument_a_when_conflict() {
+    let res = cmd().try_get_matches_from(vec!["prog", "aaa", "-b", "bbb", "-c", "ccc"]);
+    assert!(res.is_err());
+    let err = res.unwrap_err();
+    assert_eq!(err.kind(), ErrorKind::ArgumentConflict);
+    assert_eq!(
+        err.to_string(),
+        "error: The argument '-b <b>' cannot be used with '-c <c>'
+
+USAGE:
+    prog -b <b> <a>
+
+For more information try --help
+"
+    );
+}