From 07720dd1208e31f45cb20317cb15aa789428508b Mon Sep 17 00:00:00 2001
From: Andrei Sandu <54316454+sandreim@users.noreply.github.com>
Date: Mon, 1 Apr 2024 12:23:44 +0300
Subject: [PATCH] Improve `HostConfiguration` consistency check (#3897)

fixes https://github.com/paritytech/polkadot-sdk/issues/3886

---------

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>
---
 polkadot/runtime/parachains/src/configuration.rs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/polkadot/runtime/parachains/src/configuration.rs b/polkadot/runtime/parachains/src/configuration.rs
index b7635dcd7b..17022272c0 100644
--- a/polkadot/runtime/parachains/src/configuration.rs
+++ b/polkadot/runtime/parachains/src/configuration.rs
@@ -187,7 +187,7 @@ pub struct HostConfiguration<BlockNumber> {
 	///
 	/// Must be at least 1.
 	pub no_show_slots: u32,
-	/// The number of delay tranches in total.
+	/// The number of delay tranches in total. Must be at least 1.
 	pub n_delay_tranches: u32,
 	/// The width of the zeroth delay tranche for approval assignments. This many delay tranches
 	/// beyond 0 are all consolidated to form a wide 0 tranche.
@@ -247,7 +247,7 @@ impl<BlockNumber: Default + From<u32>> Default for HostConfiguration<BlockNumber
 			max_validators: None,
 			dispute_period: 6,
 			dispute_post_conclusion_acceptance_period: 100.into(),
-			n_delay_tranches: Default::default(),
+			n_delay_tranches: 1,
 			zeroth_delay_tranche_width: Default::default(),
 			needed_approvals: Default::default(),
 			relay_vrf_modulo_samples: Default::default(),
@@ -315,6 +315,8 @@ pub enum InconsistentError<BlockNumber> {
 	LookaheadExceedsTTL,
 	/// Passed in queue size for on-demand was too large.
 	OnDemandQueueSizeTooLarge,
+	/// Number of delay tranches cannot be 0.
+	ZeroDelayTranches,
 }
 
 impl<BlockNumber> HostConfiguration<BlockNumber>
@@ -412,6 +414,10 @@ where
 			return Err(OnDemandQueueSizeTooLarge)
 		}
 
+		if self.n_delay_tranches.is_zero() {
+			return Err(ZeroDelayTranches)
+		}
+
 		Ok(())
 	}