Unnecessary computing of message witness when no new certificate and last certified height

[mitsuaki-u]

Expected behavior

In chain connector plugin => newBlockHandler => computeCCUParams method, when no new certificate and last certified height === 0, there is an early return.

Actual behavior

Currently on every new block received we execute the following logic to calculate message witness:

const lastSentCCM = (await this._chainConnectorStore.getLastSentCCM()) ?? {
			nonce: DEFAULT_LAST_CCM_SENT_NONCE,
			height: this._lastCertificate.height,
		};

		let activeValidatorsUpdate: ActiveValidatorsUpdate = {
			blsKeysUpdate: [],
			bftWeightsUpdate: [],
			bftWeightsUpdateBitmap: EMPTY_BYTES,
		};
		let certificate = EMPTY_BYTES;
		let certificateThreshold;
		let outboxRootWitness;

		// Take range from lastSentCCM height until new or last certificate height
		const ccmsToBeIncluded = ccmsFromEvents.filter(
			record =>
				record.height >= lastSentCCM.height &&
				// If no newCertificate then use lastCertificate height
				record.height <= (newCertificate ? newCertificate.height : this._lastCertificate.height),
		);
		// Calculate messageWitnessHashes for pending CCMs if any
		const channelDataOnReceivingChain = await this._receivingChainClient.invoke<ChannelDataJSON>(
			'interoperability_getChannel',
			{ chainID: this._ownChainID.toString('hex') },
		);
		if (!channelDataOnReceivingChain?.inbox) {
			this.logger.info('Receiving chain is not registered yet on the sending chain.');
			return;
		}
		const inboxSizeOnReceivingChain = channelDataJSONToObj(channelDataOnReceivingChain).inbox.size;

		const receivingChainChannelDataJSON = await this._sendingChainClient.invoke<ChannelDataJSON>(
			'interoperability_getChannel',
			{ chainID: this._receivingChainID.toString('hex') },
		);

		if (!receivingChainChannelDataJSON?.outbox) {
			this.logger.info('Sending chain is not registered yet on the receiving chain.');
			return;
		}
		const outboxSizeOnSendingChain = channelDataJSONToObj(receivingChainChannelDataJSON).outbox
			.size;
		const messageWitnessHashesForCCMs = calculateMessageWitnesses(
			inboxSizeOnReceivingChain,
			outboxSizeOnSendingChain,
			lastSentCCM,
			ccmsToBeIncluded,
			this._maxCCUSize,
		);

However, we can avoid unnecessarily executing this logic upon every new bloc received when there is no new certificate and last certified height === 0 since we have this information earlier on in the logic.

Steps to reproduce

Check chain connector newBlockHandler logic

Which version(s) does this affect? (Environment, OS, etc...)

v6.0