fix round change when collatorset is empty + log in runtime

Cargo.toml

@@ -9,6 +9,9 @@ resolver = "2"
 
 [profile.production]
 codegen-units = 1
+features = [
+  "on-chain-release-build",
+]
 inherits = "release"
 lto = true
 strip = "symbols"

pallets/parachain-staking/src/lib.rs

@@ -1711,7 +1711,7 @@ pub mod pallet {
             // choose the top TotalSelected qualified candidates, ordered by stake
             let collators = Self::compute_top_candidates();
             if collators.is_empty() {
-                // SELECTION FAILED TO SELECT >=1 COLLATOR => select collators from previous round
+                log::error!("FAILED TO SELECT >=1 COLLATOR => using collators from previous round");
                 let last_round = now.saturating_sub(1u32);
                 let mut total_per_candidate: BTreeMap<T::AccountId, BalanceOf<T>> = BTreeMap::new();
                 // set this round AtStake to last round AtStake

runtime/calamari/Cargo.toml

@@ -269,3 +269,9 @@ std = [
   'pallet-manta-sbt/std',
   'manta-support/std',
 ]
+# A feature that should be enabled when the runtime should be build for on-chain
+# deployment. This will disable stuff that shouldn't be part of the on-chain wasm
+# to make it smaller like logging for example.
+on-chain-release-build = [
+  "sp-api/disable-logging",
+]

runtime/manta/Cargo.toml

@@ -248,3 +248,9 @@ std = [
   'orml-traits/std',
   'orml-xtokens/std',
 ]
+# A feature that should be enabled when the runtime should be build for on-chain
+# deployment. This will disable stuff that shouldn't be part of the on-chain wasm
+# to make it smaller like logging for example.
+on-chain-release-build = [
+  "sp-api/disable-logging",
+]

runtime/manta/src/lib.rs

@@ -1034,7 +1034,15 @@ impl_runtime_apis! {
                 // manually check aura eligibility (in the new round)
                 // mirrors logic in `aura_style_filter`
                 let truncated_half_slot = (slot >> 1) as usize;
-                let active: Vec<AccountId> = pallet_parachain_staking::Pallet::<Self>::compute_top_candidates();
+                let mut active: Vec<AccountId> = pallet_parachain_staking::Pallet::<Self>::compute_top_candidates();
+                if active.is_empty() {
+                    // `SelectedCandidates` remains unchanged from last round (fallback)
+                    active = pallet_parachain_staking::Pallet::<Self>::selected_candidates();
+                    if active.is_empty() {
+                        log::error!("NimbusApi::can_author found no valid authors");
+                        return false;
+                    }
+                }
                 account == active[truncated_half_slot % active.len()]
             } else {
                 // We're not changing rounds, `PotentialAuthors` is not changing, just use can_author