From 42122787d75cff83a7ce97a7dd2129b9a4d8cd69 Mon Sep 17 00:00:00 2001
From: Ed Page <eopage@gmail.com>
Date: Fri, 30 Sep 2022 12:24:18 -0500
Subject: [PATCH] feat(derive): Report the group id

This will be needed when we support flattening for #3165
---
 clap_derive/src/derives/args.rs | 12 +++++++++++-
 tests/derive/groups.rs          |  9 +++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/clap_derive/src/derives/args.rs b/clap_derive/src/derives/args.rs
index a92d02ee8dc..21786505a82 100644
--- a/clap_derive/src/derives/args.rs
+++ b/clap_derive/src/derives/args.rs
@@ -90,6 +90,13 @@ pub fn gen_for_struct(
     let augmentation = gen_augment(fields, &app_var, item, false);
     let augmentation_update = gen_augment(fields, &app_var, item, true);
 
+    let group_id = if item.skip_group() {
+        quote!(None)
+    } else {
+        let group_id = item.ident().unraw().to_string();
+        quote!(Some(clap::Id::from(#group_id)))
+    };
+
     quote! {
         #[allow(dead_code, unreachable_code, unused_variables, unused_braces)]
         #[allow(
@@ -140,6 +147,9 @@ pub fn gen_for_struct(
         )]
         #[deny(clippy::correctness)]
         impl #impl_generics clap::Args for #item_name #ty_generics #where_clause {
+            fn group_id() -> Option<clap::Id> {
+                #group_id
+            }
             fn augment_args<'b>(#app_var: clap::Command) -> clap::Command {
                 #augmentation
             }
@@ -313,11 +323,11 @@ pub fn gen_augment(
         quote!()
     };
     let initial_app_methods = parent_item.initial_top_level_methods();
-    let group_id = parent_item.ident().unraw().to_string();
     let final_app_methods = parent_item.final_top_level_methods();
     let group_app_methods = if parent_item.skip_group() {
         quote!()
     } else {
+        let group_id = parent_item.ident().unraw().to_string();
         let literal_group_members = fields
             .iter()
             .filter_map(|(_field, item)| {
diff --git a/tests/derive/groups.rs b/tests/derive/groups.rs
index 99cba73ef98..23a9fff3685 100644
--- a/tests/derive/groups.rs
+++ b/tests/derive/groups.rs
@@ -53,6 +53,10 @@ Usage: prog --add <CRATES|--path <PATH>|--git <GIT>>
 For more information try '--help'
 ";
     assert_output::<Opt>("prog --add", OUTPUT, true);
+
+    use clap::Args;
+    assert_eq!(Source::group_id(), Some(clap::Id::from("Source")));
+    assert_eq!(Opt::group_id(), Some(clap::Id::from("Opt")));
 }
 
 #[test]
@@ -80,4 +84,9 @@ fn skip_group_avoids_duplicate_ids() {
 
     use clap::CommandFactory;
     Opt::command().debug_assert();
+
+    use clap::Args;
+    assert_eq!(Empty::group_id(), None);
+    assert_eq!(Compose::<Empty, Empty>::group_id(), None);
+    assert_eq!(Opt::group_id(), Some(clap::Id::from("Opt")));
 }