Implement detailed logging for XCM failures

cumulus/pallets/xcmp-queue/src/lib.rs

@@ -557,8 +557,11 @@ impl<T: Config> Pallet<T> {
 			new_page.extend_from_slice(&encoded_fragment[..]);
 			let last_page_size = new_page.len();
 			let number_of_pages = (channel_details.last_index - channel_details.first_index) as u32;
-			let bounded_page = BoundedVec::<u8, T::MaxPageSize>::try_from(new_page)
-				.map_err(|_| MessageSendError::TooBig)?;
+			let bounded_page =
+				BoundedVec::<u8, T::MaxPageSize>::try_from(new_page).map_err(|error| {
+					log::debug!(target: LOG_TARGET, "Failed to create bounded message page: {error:?}");
+					MessageSendError::TooBig
+				})?;
 			let bounded_page = WeakBoundedVec::force_from(bounded_page.into_inner(), None);
 			<OutboundXcmpMessages<T>>::insert(recipient, page_index, bounded_page);
 			<OutboundXcmpStatus<T>>::put(all_channels);
@@ -585,14 +588,19 @@ impl<T: Config> Pallet<T> {
 		if let Some(details) = s.iter_mut().find(|item| item.recipient == dest) {
 			details.signals_exist = true;
 		} else {
-			s.try_push(OutboundChannelDetails::new(dest).with_signals())
-				.map_err(|_| Error::<T>::TooManyActiveOutboundChannels)?;
+			s.try_push(OutboundChannelDetails::new(dest).with_signals()).map_err(|error| {
+				log::debug!(target: LOG_TARGET, "Failed to activate XCMP channel: {error:?}");
+				Error::<T>::TooManyActiveOutboundChannels
+			})?;
 		}
 
 		let page = BoundedVec::<u8, T::MaxPageSize>::try_from(
 			(XcmpMessageFormat::Signals, signal).encode(),
 		)
-		.map_err(|_| Error::<T>::TooBig)?;
+		.map_err(|error| {
+			log::debug!(target: LOG_TARGET, "Failed to encode signal message: {error:?}");
+			Error::<T>::TooBig
+		})?;
 		let page = WeakBoundedVec::force_from(page.into_inner(), None);
 
 		<SignalMessages<T>>::insert(dest, page);
@@ -699,9 +707,16 @@ impl<T: Config> Pallet<T> {
 			return Err(())
 		}
 
-		let xcm = VersionedXcm::<()>::decode_with_depth_limit(MAX_XCM_DECODE_DEPTH, data)
-			.map_err(|_| ())?;
-		Ok(Some(xcm.encode().try_into().map_err(|_| ())?))
+		let xcm = VersionedXcm::<()>::decode_with_depth_limit(MAX_XCM_DECODE_DEPTH, data).map_err(
+			|error| {
+				log::debug!(target: LOG_TARGET, "Failed to decode XCM with depth limit: {error:?}");
+				()
+			},
+		)?;
+		Ok(Some(xcm.encode().try_into().map_err(|error| {
+			log::debug!(target: LOG_TARGET, "Failed to encode XCM after decoding: {error:?}");
+			()
+		})?))
 	}
 
 	/// Split concatenated encoded `VersionedXcm`s or `MaybeDoubleEncodedVersionedXcm`s into

cumulus/parachains/common/src/xcm_config.rs

@@ -45,6 +45,11 @@ where
 		<Runtime as pallet_assets::Config<AssetInstance>>::AssetId,
 		<Runtime as pallet_assets::Config<AssetInstance>>::Balance,
 	>,
+	<BalanceConverter as ConversionToAssetBalance<
+		CurrencyBalance,
+		<Runtime as pallet_assets::Config<AssetInstance>>::AssetId,
+		<Runtime as pallet_assets::Config<AssetInstance>>::Balance,
+	>>::Error: core::fmt::Debug,
 {
 	fn charge_weight_in_fungibles(
 		asset_id: <pallet_assets::Pallet<Runtime, AssetInstance> as Inspect<
@@ -59,7 +64,10 @@ where
 		// If the amount gotten is not at least the ED, then make it be the ED of the asset
 		// This is to avoid burning assets and decreasing the supply
 		let asset_amount = BalanceConverter::to_asset_balance(amount, asset_id)
-			.map_err(|_| XcmError::TooExpensive)?;
+			.map_err(|error| {
+				log::debug!(target: "xcm::charge_weight_in_fungibles", "AssetFeeAsExistentialDepositMultiplier cannot convert to valid balance (possibly below ED): {error:?}");
+				XcmError::TooExpensive
+			})?;
 		Ok(asset_amount)
 	}
 }

polkadot/runtime/common/src/xcm_sender.rs

@@ -136,7 +136,13 @@ where
 		let hash = sp_io::hashing::blake2_256(&blob[..]);
 		dmp::Pallet::<T>::queue_downward_message(&config, para, blob)
 			.map(|()| hash)
-			.map_err(|_| SendError::Transport(&"Error placing into DMP queue"))
+			.map_err(|error| {
+				log::debug!(
+					target: "xcm::xcm_sender::deliver",
+					"Failed to place into DMP queue: error: {error:?}, id: {hash:?}",
+				);
+				SendError::Transport(&"Error placing into DMP queue")
+			})
 	}
 
 	#[cfg(feature = "runtime-benchmarks")]

polkadot/runtime/parachains/src/dmp.rs

@@ -66,7 +66,7 @@ mod tests;
 const THRESHOLD_FACTOR: u32 = 2;
 
 /// An error sending a downward message.
-#[cfg_attr(test, derive(Debug))]
+#[derive(Debug)]
 pub enum QueueDownwardMessageError {
 	/// The message being sent exceeds the configured max message size.
 	ExceedsMaxMessageSize,