Connect EVM with EVM: Add support for skipping FQ v2 config if already configured during migration

Author: HelloKashif

deployment/ccip/changeset/v1_6/cs_update_bidirectional_lanes.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/Masterminds/semver/v3"
 
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
 
 	fqv2ops "github.com/smartcontractkit/chainlink-ccip/chains/evm/deployment/v2_0_0/operations/fee_quoter"
@@ -308,6 +309,10 @@ func UpdateLanesLogic(e cldf.Environment, mcmsConfig *proposalutils.TimelockConf
 			if err != nil {
 				return cldf.ChangesetOutput{}, fmt.Errorf("failed to convert v1.6 fee quoter destination updates for chain %d: %w", chainSel, err)
 			}
+			destCfgs, err = FilterOutExistingDestChainConfigs(e, dests.Address, chainSel, destCfgs)
+			if err != nil {
+				return cldf.ChangesetOutput{}, err
+			}
 			fqUpdate.DestChainConfigs = destCfgs
 		}
 		if prices, ok := feeQuoterPricesInput.UpdatesByChain[chainSel]; ok {
@@ -349,6 +354,38 @@ func UpdateLanesLogic(e cldf.Environment, mcmsConfig *proposalutils.TimelockConf
 	return output, nil
 }
 
+// FilterOutExistingDestChainConfigs queries the on-chain v2 FeeQuoter and removes
+// destination chain configs that are already enabled. This prevents overwriting existing
+// configurations during lane updates when a destination was previously configured.
+func FilterOutExistingDestChainConfigs(
+	e cldf.Environment,
+	fqAddr common.Address,
+	chainSel uint64,
+	destCfgs []fqv2ops.DestChainConfigArgs,
+) ([]fqv2ops.DestChainConfigArgs, error) {
+	fqContract, err := fqv2ops.NewFeeQuoterContract(fqAddr, e.BlockChains.EVMChains()[chainSel].Client)
+	if err != nil {
+		return nil, fmt.Errorf("failed to bind v2 FeeQuoter on chain %d: %w", chainSel, err)
+	}
+	filtered := make([]fqv2ops.DestChainConfigArgs, 0, len(destCfgs))
+	for _, destCfg := range destCfgs {
+		existing, err := fqContract.GetDestChainConfig(&bind.CallOpts{Context: e.GetContext()}, destCfg.DestChainSelector)
+		if err != nil {
+			return nil, fmt.Errorf("failed to query existing dest chain config on chain %d for dest %d: %w",
+				chainSel, destCfg.DestChainSelector, err)
+		}
+		if existing.IsEnabled {
+			e.Logger.Infow("skipping dest chain config already present on v2 FeeQuoter",
+				"sourceChain", chainSel,
+				"destChain", destCfg.DestChainSelector,
+			)
+			continue
+		}
+		filtered = append(filtered, destCfg)
+	}
+	return filtered, nil
+}
+
 func ConvertV16FeeQuoterDestUpdatesToV2(in []fee_quoter.FeeQuoterDestChainConfigArgs) ([]fqv2ops.DestChainConfigArgs, error) {
 	out := make([]fqv2ops.DestChainConfigArgs, 0, len(in))
 	for _, cfg := range in {

deployment/ccip/changeset/v1_6/cs_update_bidirectional_lanes_test.go

@@ -543,6 +543,78 @@ func TestUpdateBidirectionalLanesChangesetWithV2FeeQuoter(t *testing.T) {
 	}
 }
 
+func TestFilterOutExistingDestChainConfigs(t *testing.T) {
+	t.Parallel()
+
+	deployedEnvironment, _ := testhelpers.NewMemoryEnvironment(t, func(testCfg *testhelpers.TestConfigs) {
+		testCfg.Chains = 2
+	})
+	e := deployedEnvironment.Env
+
+	state, err := stateview.LoadOnchainState(e)
+	require.NoError(t, err, "must load onchain state")
+
+	selectors := e.BlockChains.ListChainSelectors(cldf_chain.WithFamily(chain_selectors.FamilyEVM))
+	require.Len(t, selectors, 2, "must have 2 chains")
+
+	chainSel := selectors[0]
+	otherChainSel := selectors[1]
+	evmChain := e.BlockChains.EVMChains()[chainSel]
+
+	parsedABI, err := abi.JSON(strings.NewReader(fqv2ops.FeeQuoterABI))
+	require.NoError(t, err, "must parse v2 FeeQuoter ABI")
+
+	// Deploy a v2 FeeQuoter with one destination already configured (otherChainSel)
+	preConfiguredDest := fqv2ops.DestChainConfigArgs{
+		DestChainSelector: otherChainSel,
+		DestChainConfig: fqv2ops.DestChainConfig{
+			IsEnabled:    true,
+			MaxDataBytes: 30_000,
+		},
+	}
+	fqV2Addr, tx, _, err := bind.DeployContract(
+		evmChain.DeployerKey,
+		parsedABI,
+		common.FromHex(fqv2ops.FeeQuoterBin),
+		evmChain.Client,
+		fqv2ops.StaticConfig{
+			MaxFeeJuelsPerMsg: big.NewInt(1e18),
+			LinkToken:         state.Chains[chainSel].LinkToken.Address(),
+		},
+		[]common.Address{evmChain.DeployerKey.From},
+		[]fqv2ops.TokenTransferFeeConfigArgs{},
+		[]fqv2ops.DestChainConfigArgs{preConfiguredDest},
+	)
+	require.NoError(t, err, "must deploy v2 FeeQuoter")
+
+	_, err = evmChain.Confirm(tx)
+	require.NoError(t, err, "must confirm v2 FeeQuoter deployment")
+
+	unconfiguredChainSel := uint64(999)
+
+	// Call FilterOutExistingDestChainConfigs with both destinations
+	input := []fqv2ops.DestChainConfigArgs{
+		{
+			DestChainSelector: otherChainSel,
+			DestChainConfig:   fqv2ops.DestChainConfig{IsEnabled: true, MaxDataBytes: 50_000},
+		},
+		{
+			DestChainSelector: unconfiguredChainSel,
+			DestChainConfig:   fqv2ops.DestChainConfig{IsEnabled: true, MaxDataBytes: 60_000},
+		},
+	}
+
+	filtered, err := v1_6.FilterOutExistingDestChainConfigs(e, fqV2Addr, chainSel, input)
+	require.NoError(t, err, "FilterOutExistingDestChainConfigs must not error")
+
+	// Only the unconfigured chain should remain
+	require.Len(t, filtered, 1, "must filter out the already-enabled destination")
+	assert.Equal(t, unconfiguredChainSel, filtered[0].DestChainSelector,
+		"remaining entry must be the unconfigured chain")
+	assert.Equal(t, uint32(60_000), filtered[0].DestChainConfig.MaxDataBytes,
+		"remaining entry must preserve original config")
+}
+
 func TestUpdateBidirectionalLanesChangesetWithV2FeeQuoterWithMCMS(t *testing.T) {
 	t.Parallel()