Fix slot-based collator panic during warp sync (#11072)

cumulus/polkadot-omni-node/lib/src/nodes/aura.rs

@@ -666,9 +666,16 @@ where
 			max_pov_percentage: node_extra_args.max_pov_percentage,
 		};
 
-		// We have a separate function only to be able to use `docify::export` on this piece of
-		// code.
-		Self::launch_slot_based_collator(params);
+		let wait_client = client.clone();
+		let fut = async move {
+			wait_for_aura::<Block, RuntimeApi, AuraId>(wait_client).await;
+			// We have a separate function only to be able to use `docify::export` on this
+			// piece of code.
+			Self::launch_slot_based_collator(params);
+		};
+		task_manager
+			.spawn_essential_handle()
+			.spawn("slot-based-collator-init", None, fut);
 
 		Ok(())
 	}

prdoc/pr_11381.prdoc

@@ -0,0 +1,23 @@
+title: Fix slot-based collator panic during warp sync (#11072)
+doc:
+- audience: Node Dev
+  description: |-
+    When a parachain collator starts with `--authoring=slot-based` and performs warp sync, the `slot-based-block-builder` essential task immediately calls `slot_duration()` which requires `AuraApi_slot_duration`. During warp sync the runtime isn't ready, so this fails and the task returns, shutting down the node.
+
+    The lookahead collator avoids this by calling `wait_for_aura()` before starting. This PR adds an equivalent guard to the slot-based collator.
+
+    ### Manual test
+    Before the fix the collator panicked after the relay chain warp sync with AuraApi_slot_duration not available, which does not occur anymore now.
+    ```
+     ./target/release/polkadot-parachain \
+        --chain asset-hub-polkadot \
+        --sync warp \
+        --authoring=slot-based \
+        --tmp -- --sync warp
+    ```
+    Closes #11072.
+crates:
+- name: cumulus-client-consensus-aura
+  bump: patch
+- name: polkadot-omni-node-lib
+  bump: patch