From aff0445b247e02869453220f433339ca5971fc10 Mon Sep 17 00:00:00 2001
From: Gavin Wood <gavin@parity.io>
Date: Mon, 10 Feb 2020 14:04:50 +0100
Subject: [PATCH] Avoid challenging those that can't be suspended anyway
 (#4804)

* Merge branch 'gav-split-balanecs-vesting' into gav-upsub

# Conflicts:
#	Cargo.lock
#	cli/Cargo.toml
#	collator/Cargo.toml
#	primitives/Cargo.toml
#	runtime/common/Cargo.toml
#	runtime/common/src/claims.rs
#	runtime/kusama/Cargo.toml
#	runtime/polkadot/Cargo.toml
#	service/Cargo.toml

* Fix tests
---
 substrate/frame/society/src/lib.rs   | 30 +++++++++++++++++-----------
 substrate/frame/society/src/tests.rs | 14 ++++++-------
 2 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/substrate/frame/society/src/lib.rs b/substrate/frame/society/src/lib.rs
index c1e1803c64..28220f1063 100644
--- a/substrate/frame/society/src/lib.rs
+++ b/substrate/frame/society/src/lib.rs
@@ -1536,18 +1536,24 @@ impl<T: Trait<I>, I: Instance> Module<T, I> {
 				<DefenderVotes<T, I>>::remove_all();
 			}
 
-			// Start a new defender rotation
-			let phrase = b"society_challenge";
-			// we'll need a random seed here.
-			let seed = T::Randomness::random(phrase);
-			// seed needs to be guaranteed to be 32 bytes.
-			let seed = <[u8; 32]>::decode(&mut TrailingZeroInput::new(seed.as_ref()))
-				.expect("input is padded with zeroes; qed");
-			let mut rng = ChaChaRng::from_seed(seed);
-			let chosen = pick_item(&mut rng, &members).expect("exited if members empty; qed");
-
-			<Defender<T, I>>::put(&chosen);
-			Self::deposit_event(RawEvent::Challenged(chosen.clone()));
+			// Avoid challenging if there's only two members since we never challenge the Head or
+			// the Founder.
+			if members.len() > 2 {
+				// Start a new defender rotation
+				let phrase = b"society_challenge";
+				// we'll need a random seed here.
+				let seed = T::Randomness::random(phrase);
+				// seed needs to be guaranteed to be 32 bytes.
+				let seed = <[u8; 32]>::decode(&mut TrailingZeroInput::new(seed.as_ref()))
+					.expect("input is padded with zeroes; qed");
+				let mut rng = ChaChaRng::from_seed(seed);
+				let chosen = pick_item(&mut rng, &members[1..members.len() - 1])
+					.expect("exited if members empty; qed");
+				<Defender<T, I>>::put(&chosen);
+				Self::deposit_event(RawEvent::Challenged(chosen.clone()));
+			} else {
+				<Defender<T, I>>::kill();
+			}
 		}
 	}
 
diff --git a/substrate/frame/society/src/tests.rs b/substrate/frame/society/src/tests.rs
index 3e5afc47f5..47d13d8361 100644
--- a/substrate/frame/society/src/tests.rs
+++ b/substrate/frame/society/src/tests.rs
@@ -577,14 +577,14 @@ fn challenges_work() {
 		assert_eq!(Society::defender(), None);
 		// 20 will be challenged during the challenge rotation
 		run_to_block(8);
-		assert_eq!(Society::defender(), Some(20));
+		assert_eq!(Society::defender(), Some(30));
 		// They can always free vote for themselves
-		assert_ok!(Society::defender_vote(Origin::signed(20), true));
+		assert_ok!(Society::defender_vote(Origin::signed(30), true));
 		// If no one else votes, nothing happens
 		run_to_block(16);
 		assert_eq!(Society::members(), vec![10, 20, 30, 40]);
 		// New challenge period
-		assert_eq!(Society::defender(), Some(20));
+		assert_eq!(Society::defender(), Some(30));
 		// Non-member cannot challenge
 		assert_noop!(Society::defender_vote(Origin::signed(1), true), Error::<Test, _>::NotMember);
 		// 3 people say accept, 1 reject
@@ -601,7 +601,7 @@ fn challenges_work() {
 		assert_eq!(<DefenderVotes<Test>>::get(30), None);
 		assert_eq!(<DefenderVotes<Test>>::get(40), None);
 		// One more time
-		assert_eq!(Society::defender(), Some(20));
+		assert_eq!(Society::defender(), Some(30));
 		// 2 people say accept, 2 reject
 		assert_ok!(Society::defender_vote(Origin::signed(10), true));
 		assert_ok!(Society::defender_vote(Origin::signed(20), true));
@@ -609,10 +609,10 @@ fn challenges_work() {
 		assert_ok!(Society::defender_vote(Origin::signed(40), false));
 		run_to_block(32);
 		// 20 is suspended
-		assert_eq!(Society::members(), vec![10, 30, 40]);
-		assert_eq!(Society::suspended_member(20), true);
+		assert_eq!(Society::members(), vec![10, 20, 40]);
+		assert_eq!(Society::suspended_member(30), true);
 		// New defender is chosen
-		assert_eq!(Society::defender(), Some(40));
+		assert_eq!(Society::defender(), Some(20));
 		// Votes are reset
 		assert_eq!(<DefenderVotes<Test>>::get(10), None);
 		assert_eq!(<DefenderVotes<Test>>::get(20), None);