multi: add decimal display to OpenChannel struct

rfqmsg/custom_channel_data.go

@@ -21,10 +21,11 @@ type JsonAssetGenesis struct {
 // JsonAssetUtxo is a struct that represents the UTXO information of an asset
 // within a channel.
 type JsonAssetUtxo struct {
-	Version      int64            `json:"version"`
-	AssetGenesis JsonAssetGenesis `json:"asset_genesis"`
-	Amount       uint64           `json:"amount"`
-	ScriptKey    string           `json:"script_key"`
+	Version        int64            `json:"version"`
+	AssetGenesis   JsonAssetGenesis `json:"asset_genesis"`
+	Amount         uint64           `json:"amount"`
+	ScriptKey      string           `json:"script_key"`
+	DecimalDisplay uint8            `json:"decimal_display"`
 }
 
 // JsonAssetChanInfo is a struct that represents the channel information of a

tapchannel/aux_funding_controller.go

@@ -541,7 +541,7 @@ func (p *pendingAssetFunding) toAuxFundingDesc(req *bindFundingReq,
 
 	// With all the outputs assembled, we'll now map that to the open
 	// channel wrapper that'll go in the set of TLV blobs.
-	openChanDesc := cmsg.NewOpenChannel(assetOutputs)
+	openChanDesc := cmsg.NewOpenChannel(assetOutputs, decimalDisplay)
 
 	// Now we'll encode the 3 TLV blobs that lnd will store: the main one
 	// for the funding details, and then the blobs for the local and remote

tapchannelmsg/custom_channel_data.go

@@ -81,6 +81,7 @@ func (c *ChannelCustomData) AsJson() ([]byte, error) {
 			ScriptKey: hex.EncodeToString(
 				a.ScriptKey.PubKey.SerializeCompressed(),
 			),
+			DecimalDisplay: c.OpenChan.DecimalDisplay.Val,
 		}
 		resp.Assets = append(resp.Assets, rfqmsg.JsonAssetChanInfo{
 			AssetInfo:     utxo,

tapchannelmsg/records.go

@@ -86,16 +86,28 @@ type OpenChannel struct {
 	// FundedAssets is a list of asset outputs that was committed to the
 	// funding output of a commitment.
 	FundedAssets tlv.RecordT[tlv.TlvType0, AssetOutputListRecord]
+
+	// DecimalDisplay is the asset's unit precision. We place this value on
+	// the channel directly and not into each funding asset balance struct
+	// since even for a channel with multiple tranches of fungible assets,
+	// this value needs to be the same for all assets. Otherwise, they would
+	// not be fungible.
+	DecimalDisplay tlv.RecordT[tlv.TlvType1, uint8]
 }
 
 // NewOpenChannel creates a new OpenChannel record with the given funded assets.
-func NewOpenChannel(fundedAssets []*AssetOutput) *OpenChannel {
+func NewOpenChannel(fundedAssets []*AssetOutput,
+	decimalDisplay uint8) *OpenChannel {
+
 	return &OpenChannel{
 		FundedAssets: tlv.NewRecordT[tlv.TlvType0](
 			AssetOutputListRecord{
 				Outputs: fundedAssets,
 			},
 		),
+		DecimalDisplay: tlv.NewPrimitiveRecord[tlv.TlvType1](
+			decimalDisplay,
+		),
 	}
 }
 
@@ -109,6 +121,7 @@ func (o *OpenChannel) Assets() []*AssetOutput {
 func (o *OpenChannel) records() []tlv.Record {
 	return []tlv.Record{
 		o.FundedAssets.Record(),
+		o.DecimalDisplay.Record(),
 	}
 }
 

tapchannelmsg/records_test.go

@@ -76,14 +76,14 @@ func TestOpenChannel(t *testing.T) {
 			name: "channel with funded asset",
 			channel: NewOpenChannel([]*AssetOutput{
 				NewAssetOutput([32]byte{1}, 1000, *randProof),
-			}),
+			}, 0),
 		},
 		{
 			name: "channel with multiple funded assets",
 			channel: NewOpenChannel([]*AssetOutput{
 				NewAssetOutput([32]byte{1}, 1000, *randProof),
 				NewAssetOutput([32]byte{2}, 2000, *randProof),
-			}),
+			}, 11),
 		},
 	}