[walletrpc]: add sat_per_kw fee option to FundPsbt RPC

cmd/lncli/walletrpc_active.go

@@ -1160,7 +1160,8 @@ var fundPsbtCommand = cli.Command{
 	Name:  "fund",
 	Usage: "Fund a Partially Signed Bitcoin Transaction (PSBT).",
 	ArgsUsage: "[--template_psbt=T | [--outputs=O [--inputs=I]]] " +
-		"[--conf_target=C | --sat_per_vbyte=S] [--change_type=A]",
+		"[--conf_target=C | --sat_per_vbyte=S | --sat_per_kw=K] " +
+		"[--change_type=A]",
 	Description: `
 	The fund command creates a fully populated PSBT that contains enough
 	inputs to fund the outputs specified in either the PSBT or the
@@ -1222,6 +1223,11 @@ var fundPsbtCommand = cli.Command{
 			Usage: "a manual fee expressed in sat/vbyte that " +
 				"should be used when creating the transaction",
 		},
+		cli.Uint64Flag{
+			Name: "sat_per_kw",
+			Usage: "a manual fee expressed in sat/kw that " +
+				"should be used when creating the transaction",
+		},
 		cli.StringFlag{
 			Name: "account",
 			Usage: "(optional) the name of the account to use to " +
@@ -1302,10 +1308,11 @@ func fundPsbt(ctx *cli.Context) error {
 		)
 
 		if len(ctx.String("outputs")) > 0 {
-			// Parse the address to amount map as JSON now. At least one
-			// entry must be present.
+			// Parse the address to amount map as JSON now. At least
+			// one entry must be present.
 			jsonMap := []byte(ctx.String("outputs"))
-			if err := json.Unmarshal(jsonMap, &amountToAddr); err != nil {
+			err := json.Unmarshal(jsonMap, &amountToAddr)
+			if err != nil {
 				return fmt.Errorf("error parsing outputs "+
 					"JSON: %w", err)
 			}
@@ -1317,7 +1324,8 @@ func fundPsbt(ctx *cli.Context) error {
 			var inputs []string
 
 			jsonList := []byte(ctx.String("inputs"))
-			if err := json.Unmarshal(jsonList, &inputs); err != nil {
+			err := json.Unmarshal(jsonList, &inputs)
+			if err != nil {
 				return fmt.Errorf("error parsing inputs JSON: "+
 					"%v", err)
 			}
@@ -1344,15 +1352,23 @@ func fundPsbt(ctx *cli.Context) error {
 
 	// Parse fee flags.
 	switch {
-	case ctx.IsSet("conf_target") && ctx.IsSet("sat_per_vbyte"):
-		return fmt.Errorf("cannot set conf_target and sat_per_vbyte " +
-			"at the same time")
+	case ctx.IsSet("conf_target") && ctx.IsSet("sat_per_vbyte") ||
+		ctx.IsSet("conf_target") && ctx.IsSet("sat_per_kw") ||
+		ctx.IsSet("sat_per_vbyte") && ctx.IsSet("sat_per_kw"):
+
+		return fmt.Errorf("only one of conf_target, sat_per_vbyte, " +
+			"or sat_per_kw can be set at the same time")
 
 	case ctx.Uint64("sat_per_vbyte") > 0:
 		req.Fees = &walletrpc.FundPsbtRequest_SatPerVbyte{
 			SatPerVbyte: ctx.Uint64("sat_per_vbyte"),
 		}
 
+	case ctx.Uint64("sat_per_kw") > 0:
+		req.Fees = &walletrpc.FundPsbtRequest_SatPerKw{
+			SatPerKw: ctx.Uint64("sat_per_kw"),
+		}
+
 	// Check conf_target last because it has a default value.
 	case ctx.Uint64("conf_target") > 0:
 		req.Fees = &walletrpc.FundPsbtRequest_TargetConf{

docs/release-notes/release-notes-0.19.0.md

@@ -31,8 +31,16 @@
   `BumpForceCloseFee` which moves the functionality soley available in the
   `lncli` to LND hence making it more universal.
 
+* [The `walletrpc.FundPsbt` RPC method now has an option to specify the fee as
+  `sat_per_kw` which allows for more precise
+  fees](https://github.com/lightningnetwork/lnd/pull/9013).
+
 ## lncli Additions
 
+* [The `lncli wallet fundpsbt` sub command now has a `--sat_per_kw` flag to
+  specify more precise fee
+  rates](https://github.com/lightningnetwork/lnd/pull/9013).
+
 # Improvements
 ## Functional Updates
 

lnrpc/walletrpc/walletkit.proto

@@ -1388,6 +1388,12 @@ message FundPsbtRequest {
         input with.
         */
         uint64 sat_per_vbyte = 4;
+
+        /*
+        The fee rate, expressed in sat/kWU, that should be used to spend the
+        input with.
+        */
+        uint64 sat_per_kw = 11;
     }
 
     /*

lnrpc/walletrpc/walletkit.swagger.json

@@ -1564,6 +1564,11 @@
           "format": "uint64",
           "description": "The fee rate, expressed in sat/vbyte, that should be used to spend the\ninput with."
         },
+        "sat_per_kw": {
+          "type": "string",
+          "format": "uint64",
+          "description": "The fee rate, expressed in sat/kWU, that should be used to spend the\ninput with."
+        },
         "account": {
           "type": "string",
           "description": "The name of the account to fund the PSBT with. If empty, the default wallet\naccount is used."

lnrpc/walletrpc/walletkit_server.go

@@ -1502,9 +1502,13 @@ func (w *WalletKit) FundPsbt(_ context.Context,
 			req.GetSatPerVbyte() * 1000,
 		).FeePerKWeight()
 
+	case req.GetSatPerKw() != 0:
+		feeSatPerKW = chainfee.SatPerKWeight(req.GetSatPerKw())
+
 	default:
 		return nil, fmt.Errorf("fee definition missing, need to " +
-			"specify either target_conf or sat_per_vbyte")
+			"specify either target_conf, sat_per_vbyte or " +
+			"sat_per_kw")
 	}
 
 	// Then, we'll extract the minimum number of confirmations that each