cmd/commands: add --qr flag to addinvoice for terminal QR display

Add a `--qr` flag to the `addinvoice` CLI command that renders the
payment request as a QR code directly in the terminal using the
qrterminal library. This makes it convenient to scan invoices from
a mobile wallet without needing to copy-paste the payment request
string.

Author: hieblmi

cmd/commands/cmd_invoice.go

@@ -3,10 +3,12 @@ package commands
 import (
 	"encoding/hex"
 	"fmt"
+	"os"
 	"strconv"
 	"strings"
 
 	"github.com/lightningnetwork/lnd/lnrpc"
+	qrterminal "github.com/mdp/qrterminal/v3"
 	"github.com/urfave/cli"
 	"google.golang.org/protobuf/proto"
 )
@@ -124,6 +126,11 @@ var AddInvoiceCommand = cli.Command{
 				"id (separated by commas), starting from a " +
 				"channel which points to the self node.",
 		},
+		cli.BoolFlag{
+			Name: "qr",
+			Usage: "display a QR code of the payment request " +
+				"in the terminal",
+		},
 	},
 	Action: actionDecorator(addInvoice),
 }
@@ -202,6 +209,15 @@ func addInvoice(ctx *cli.Context) error {
 
 	printRespJSON(resp)
 
+	if ctx.Bool("qr") {
+		// If the user requested it, we'll also print a QR code that
+		// encodes the payment request for easy scanning.
+		fmt.Println()
+		qrterminal.GenerateHalfBlock(
+			resp.PaymentRequest, qrterminal.L, os.Stdout,
+		)
+	}
+
 	return nil
 }
 

go.mod

@@ -130,6 +130,7 @@ require (
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/mattn/go-runewidth v0.0.13 // indirect
 	github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
+	github.com/mdp/qrterminal/v3 v3.2.1
 	github.com/moby/docker-image-spec v1.3.1 // indirect
 	github.com/moby/term v0.5.0 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
@@ -199,6 +200,7 @@ require (
 	modernc.org/sqlite v1.29.10 // indirect
 	modernc.org/strutil v1.2.0 // indirect
 	modernc.org/token v1.1.0 // indirect
+	rsc.io/qr v0.2.0 // indirect
 	sigs.k8s.io/yaml v1.2.0 // indirect
 )
 

go.sum

@@ -405,6 +405,8 @@ github.com/mattn/go-runewidth v0.0.13 h1:lTGmDsbAYt5DmK6OnoV7EuIF1wEIFAcxld6ypU4
 github.com/mattn/go-runewidth v0.0.13/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
 github.com/matttproud/golang_protobuf_extensions v1.0.1 h1:4hp9jkHxhMHkqkrB3Ix0jegS5sx/RkqARlsWZ6pIwiU=
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
+github.com/mdp/qrterminal/v3 v3.2.1 h1:6+yQjiiOsSuXT5n9/m60E54vdgFsw0zhADHhHLrFet4=
+github.com/mdp/qrterminal/v3 v3.2.1/go.mod h1:jOTmXvnBsMy5xqLniO0R++Jmjs2sTm9dFSuQ5kpz/SU=
 github.com/miekg/dns v1.1.43 h1:JKfpVSCB84vrAmHzyrsxB5NAr5kLoMXZArPSw7Qlgyg=
 github.com/miekg/dns v1.1.43/go.mod h1:+evo5L0630/F6ca/Z9+GAqzhjGyn8/c+TBaOyfEl0V4=
 github.com/moby/docker-image-spec v1.3.1 h1:jMKff3w6PgbfSa69GfNg+zN/XLhfXJGnEx3Nl2EsFP0=
@@ -852,5 +854,7 @@ modernc.org/token v1.1.0 h1:Xl7Ap9dKaEs5kLoOQeQmPWevfnk/DM5qcLcYlA8ys6Y=
 modernc.org/token v1.1.0/go.mod h1:UGzOrNV1mAFSEB63lOFHIpNRUVMvYTc6yu1SMY/XTDM=
 pgregory.net/rapid v1.2.0 h1:keKAYRcjm+e1F0oAuU5F5+YPAWcyxNNRK2wud503Gnk=
 pgregory.net/rapid v1.2.0/go.mod h1:PY5XlDGj0+V1FCq0o192FdRhpKHGTRIWBgqjDBTrq04=
+rsc.io/qr v0.2.0 h1:6vBLea5/NRMVTz8V66gipeLycZMl/+UlFmk8DvqQ6WY=
+rsc.io/qr v0.2.0/go.mod h1:IF+uZjkb9fqyeF/4tlBoynqmQxUoPfWEKh921coOuXs=
 sigs.k8s.io/yaml v1.2.0 h1:kr/MCeFWJWTwyaHoR9c8EjH9OumOmoF9YGiZd7lFm/Q=
 sigs.k8s.io/yaml v1.2.0/go.mod h1:yfXDCHCao9+ENCvLSE62v9VSji2MKu5jeNfTrofGhJc=