refactor: improve invalid subcommand handling (#335)

src/matcher.rs

@@ -798,7 +798,9 @@ impl<'a, 'b, T: Runtime> Matcher<'a, 'b, T> {
                 if self.positional_args.is_empty() && last_args.is_empty() {
                     return Some(MatchError::DisplayHelp);
                 } else {
-                    return Some(MatchError::InvalidSubcommand(None));
+                    return Some(MatchError::InvalidSubcommand(
+                        self.positional_args.first().map(|v| v.to_string()),
+                    ));
                 }
             } else if last_cmd.positional_params.is_empty() && !self.positional_args.is_empty() {
                 return Some(MatchError::InvalidSubcommand(
@@ -982,13 +984,13 @@ impl<'a, 'b, T: Runtime> Matcher<'a, 'b, T> {
                 let cmd = self.last_cmd();
                 cmd.render_version()
             }
-            MatchError::InvalidSubcommand(name) => {
+            MatchError::InvalidSubcommand(arg) => {
                 exit = 1;
                 let cmd = self.last_cmd();
                 let cmd_str = cmd.cmd_paths().join("-");
                 let names = cmd.list_subcommand_names().join(", ");
-                let details = match name {
-                    Some(name) => format!("but '{name}' is not one of them"),
+                let details = match arg {
+                    Some(arg) => format!("but '{arg}' is not one of them"),
                     None => "but one was not provided".to_string(),
                 };
                 format!(

tests/snapshots/integration__validate__arg_invalid_subcmd.snap

@@ -7,13 +7,11 @@ prog foo
 
 # OUTPUT
 command cat >&2 <<-'EOF' 
-error: `prog` requires a subcommand but one was not provided
+error: `prog` requires a subcommand but 'foo' is not one of them
   [subcommands: cmda, cmdb]
 EOF
 exit 1
 
 # BUILD_OUTPUT
 error: `prog` requires a subcommand but one was not provided
   [subcommands: cmda, cmdb]
-
-