From 609cf063932b07c6c87ec256136c321e2be654ef Mon Sep 17 00:00:00 2001
From: Luke Parker <lukeparker5132@gmail.com>
Date: Sat, 15 Nov 2025 14:59:33 -0500
Subject: [PATCH] Update `SetDecided` to include the validators

Necessary for light-client protocols to follow along with consensus. Arguably,
anyone handling GRANDPA's consensus could peek at this through the consensus
commit anyways, but we shouldn't so defer that.
---
 substrate/abi/src/validator_sets.rs            |  4 ++++
 substrate/client/serai/Cargo.toml              |  1 +
 substrate/client/serai/tests/validator_sets.rs | 15 +++++++++++++--
 substrate/validator-sets/src/sessions.rs       | 12 +++++++++---
 4 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/substrate/abi/src/validator_sets.rs b/substrate/abi/src/validator_sets.rs
index 42576328..40b30e16 100644
--- a/substrate/abi/src/validator_sets.rs
+++ b/substrate/abi/src/validator_sets.rs
@@ -1,3 +1,5 @@
+use alloc::vec::Vec;
+
 use borsh::{BorshSerialize, BorshDeserialize};
 
 use serai_primitives::{
@@ -96,6 +98,8 @@ pub enum Event {
   SetDecided {
     /// The set decided.
     set: ValidatorSet,
+    /// The validators decided to be included in the set.
+    validators: Vec<(SeraiAddress, KeyShares)>,
   },
   /// A validator set has set their keys.
   SetKeys {
diff --git a/substrate/client/serai/Cargo.toml b/substrate/client/serai/Cargo.toml
index d5ff35eb..48fb0611 100644
--- a/substrate/client/serai/Cargo.toml
+++ b/substrate/client/serai/Cargo.toml
@@ -30,6 +30,7 @@ async-lock = "3"
 
 [dev-dependencies]
 blake2 = { version = "0.11.0-rc.3", default-features = false }
+sp-core = { git = "https://github.com/serai-dex/patch-polkadot-sdk", rev = "e01101b68c5b0f588dd4cdee48f801a2c1f75b84" }
 
 tokio = { version = "1", default-features = false, features = ["rt", "macros"] }
 dockertest = "0.5"
diff --git a/substrate/client/serai/tests/validator_sets.rs b/substrate/client/serai/tests/validator_sets.rs
index be0000d6..cc9ca300 100644
--- a/substrate/client/serai/tests/validator_sets.rs
+++ b/substrate/client/serai/tests/validator_sets.rs
@@ -1,8 +1,9 @@
 use serai_abi::{
   primitives::{
+    address::SeraiAddress,
     network_id::{ExternalNetworkId, NetworkId},
     balance::Amount,
-    validator_sets::{Session, ExternalValidatorSet, ValidatorSet},
+    validator_sets::{Session, ExternalValidatorSet, ValidatorSet, KeyShares},
   },
   validator_sets::Event,
 };
@@ -43,8 +44,13 @@ async fn validator_sets() {
         panic!("finalized block remained the genesis block for over five minutes");
       };
 
-      // The genesis block should have the expected events
       {
+        use sp_core::{Pair as _, sr25519::Pair};
+        let genesis_validators = vec![(
+          SeraiAddress::from(Pair::from_string("//Alice", None).unwrap().public()),
+          KeyShares(1),
+        )];
+        // The genesis block should have the expected events
         {
           let mut events = serai
             .as_of(serai.block_by_number(0).await.unwrap().header.hash())
@@ -58,27 +64,32 @@ async fn validator_sets() {
           let mut expected = vec![
             Event::SetDecided {
               set: ValidatorSet { network: NetworkId::Serai, session: Session(0) },
+              validators: genesis_validators.clone(),
             },
             Event::SetDecided {
               set: ValidatorSet { network: NetworkId::Serai, session: Session(1) },
+              validators: genesis_validators.clone(),
             },
             Event::SetDecided {
               set: ValidatorSet {
                 network: NetworkId::External(ExternalNetworkId::Bitcoin),
                 session: Session(0),
               },
+              validators: genesis_validators.clone(),
             },
             Event::SetDecided {
               set: ValidatorSet {
                 network: NetworkId::External(ExternalNetworkId::Ethereum),
                 session: Session(0),
               },
+              validators: genesis_validators.clone(),
             },
             Event::SetDecided {
               set: ValidatorSet {
                 network: NetworkId::External(ExternalNetworkId::Monero),
                 session: Session(0),
               },
+              validators: genesis_validators.clone(),
             },
           ];
           expected.sort_by_key(|event| borsh::to_vec(event).unwrap());
diff --git a/substrate/validator-sets/src/sessions.rs b/substrate/validator-sets/src/sessions.rs
index 0f1121e8..ed54029d 100644
--- a/substrate/validator-sets/src/sessions.rs
+++ b/substrate/validator-sets/src/sessions.rs
@@ -326,14 +326,20 @@ impl<Storage: SessionsStorage> Sessions for Storage {
       latest_decided_set,
       KeySharesStruct::try_from(total_key_shares).expect("amortization failure"),
     );
-    for (key, key_shares) in selected_validators {
+    for (key, key_shares) in &selected_validators {
       Storage::SelectedValidators::insert(
-        selected_validators_key(latest_decided_set, key),
+        selected_validators_key(latest_decided_set, *key),
         key_shares,
       );
     }
 
-    Core::<Storage::Config>::emit_event(Event::SetDecided { set: latest_decided_set });
+    Core::<Storage::Config>::emit_event(Event::SetDecided {
+      set: latest_decided_set,
+      validators: selected_validators
+        .into_iter()
+        .map(|(key, key_shares)| (key.into(), key_shares))
+        .collect(),
+    });
 
     true
   }