fix(parser): Don't report conflicting arguments in usage

Fixes #6236

Author: epage

clap_builder/src/parser/validator.rs

@@ -132,8 +132,7 @@ impl<'cmd> Validator<'cmd> {
         }
 
         debug!("Validator::build_conflict_err: name={name:?}");
-        let mut seen = FlatSet::new();
-        let conflicts = conflict_ids
+        let conflict_ids = conflict_ids
             .iter()
             .flat_map(|c_id| {
                 if self.cmd.find_group(c_id).is_some() {
@@ -142,16 +141,18 @@ impl<'cmd> Validator<'cmd> {
                     vec![c_id.clone()]
                 }
             })
-            .filter_map(|c_id| {
-                seen.insert(c_id.clone()).then(|| {
-                    let c_arg = self.cmd.find(&c_id).expect(INTERNAL_ERROR_MSG);
-                    c_arg.to_string()
-                })
+            .collect::<FlatSet<_>>()
+            .into_vec();
+        let conflicts = conflict_ids
+            .iter()
+            .map(|c_id| {
+                let c_arg = self.cmd.find(&c_id).expect(INTERNAL_ERROR_MSG);
+                c_arg.to_string()
             })
             .collect();
 
         let former_arg = self.cmd.find(name).expect(INTERNAL_ERROR_MSG);
-        let usg = self.build_conflict_err_usage(matcher, conflict_ids);
+        let usg = self.build_conflict_err_usage(matcher, &conflict_ids);
         Err(Error::argument_conflict(
             self.cmd,
             former_arg.to_string(),

clap_builder/src/util/flat_set.rs

@@ -60,6 +60,10 @@ impl<T: PartialEq + Eq> FlatSet<T> {
     {
         self.inner.sort_by_key(f);
     }
+
+    pub(crate) fn into_vec(self) -> Vec<T> {
+        self.inner
+    }
 }
 
 impl<T: PartialEq + Eq> Default for FlatSet<T> {

tests/builder/groups.rs

@@ -232,7 +232,7 @@ error: the argument '--conflict' cannot be used with:
   --a
   --b
 
-Usage: prog --a --conflict
+Usage: prog --conflict
 
 For more information, try '--help'.