lncli: strip prefix from pay_req flag

cmd/lncli/arg_parse.go

@@ -3,6 +3,7 @@ package main
 import (
 	"regexp"
 	"strconv"
+	"strings"
 	"time"
 )
 
@@ -38,3 +39,10 @@ func parseTime(s string, base time.Time) (uint64, error) {
 
 	return strconv.ParseUint(s, 10, 64)
 }
+
+var lightningPrefix = "lightning:"
+
+// stripPrefix removes accidentally copied 'lightning:' prefix.
+func stripPrefix(s string) string {
+	return strings.TrimSpace(strings.TrimPrefix(s, lightningPrefix))
+}

cmd/lncli/arg_parse_test.go

@@ -3,6 +3,8 @@ package main
 import (
 	"testing"
 	"time"
+
+	"github.com/stretchr/testify/require"
 )
 
 var now = time.Date(2017, 11, 10, 7, 8, 9, 1234, time.UTC)
@@ -86,3 +88,30 @@ func TestParseTime(t *testing.T) {
 		}
 	}
 }
+
+var stripPrefixTests = []struct {
+	in       string
+	expected string
+}{
+	{
+		"lightning:ln123",
+		"ln123",
+	},
+	{
+		"lightning: ln123",
+		"ln123",
+	},
+	{
+		"ln123",
+		"ln123",
+	},
+}
+
+func TestStripPrefix(t *testing.T) {
+	t.Parallel()
+
+	for _, test := range stripPrefixTests {
+		actual := stripPrefix(test.in)
+		require.Equal(t, test.expected, actual)
+	}
+}

cmd/lncli/cmd_invoice.go

@@ -292,7 +292,7 @@ func decodePayReq(ctx *cli.Context) error {
 	}
 
 	resp, err := client.DecodePayReq(ctxc, &lnrpc.PayReqString{
-		PayReq: payreq,
+		PayReq: stripPrefix(payreq),
 	})
 	if err != nil {
 		return err

cmd/lncli/cmd_payments.go

@@ -284,7 +284,7 @@ func sendPayment(ctx *cli.Context) error {
 	// details of the payment are encoded within the request.
 	if ctx.IsSet("pay_req") {
 		req := &routerrpc.SendPaymentRequest{
-			PaymentRequest:    ctx.String("pay_req"),
+			PaymentRequest:    stripPrefix(ctx.String("pay_req")),
 			Amt:               ctx.Int64("amt"),
 			DestCustomRecords: make(map[uint64][]byte),
 		}
@@ -832,7 +832,7 @@ func payInvoice(ctx *cli.Context) error {
 	}
 
 	req := &routerrpc.SendPaymentRequest{
-		PaymentRequest:    payReq,
+		PaymentRequest:    stripPrefix(payReq),
 		Amt:               ctx.Int64("amt"),
 		DestCustomRecords: make(map[uint64][]byte),
 	}

docs/release-notes/release-notes-0.16.0.md

@@ -174,6 +174,13 @@ certain large transactions](https://github.com/lightningnetwork/lnd/pull/7100).
 * [Label the openchannel tx first before notifying the channel open
   event.](https://github.com/lightningnetwork/lnd/pull/7158) 
 
+* [Add check for `pay_req` argument in `sendpayment` and `decodepayreq`
+  commands to trim "lightning:" prefix before processing the request](
+  https://github.com/lightningnetwork/lnd/pull/7150). Invoices may be prefixed
+  with "lightning:" on mobile and web apps and it's likely for users to copy
+  the invoice payment request together with the prefix, which throws checksum
+  error when pasting it to the CLI.
+
 ## Code Health
 
 * [test: use `T.TempDir` to create temporary test