Fix a bug in the Go code of the CSI key event parser

Fixes #6189

docs/changelog.rst

@@ -40,6 +40,8 @@ Detailed list of changes
 
 - Fix a regression in the previous release that broke the remote file kitten (:iss:`6186`)
 
+- Fix a regression in the previous release that broke handling of some key board shortcuts in some kittens on some keyboard layouts (:iss:`6189`)
+
 0.28.0 [2023-04-15]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

tools/tui/loop/key-encoding.go

@@ -140,26 +140,30 @@ func KeyEventFromCSI(csi string) *KeyEvent {
 	csi = csi[:len(csi)-1]
 	sections := strings.Split(csi, ";")
 
-	get_sub_sections := func(section string) []int {
+	get_sub_sections := func(section string, missing int) []int {
 		p := strings.Split(section, ":")
 		ans := make([]int, len(p))
 		for i, x := range p {
-			q, err := strconv.Atoi(x)
-			if err != nil {
-				return nil
+			if x == "" {
+				ans[i] = missing
+			} else {
+				q, err := strconv.Atoi(x)
+				if err != nil {
+					return nil
+				}
+				ans[i] = q
 			}
-			ans[i] = q
 		}
 		return ans
 	}
-	first_section := get_sub_sections(sections[0])
-	second_section := make([]int, 0)
-	third_section := make([]int, 0)
+	first_section := get_sub_sections(sections[0], 0)
+	second_section := []int{}
+	third_section := []int{}
 	if len(sections) > 1 {
-		second_section = get_sub_sections(sections[1])
+		second_section = get_sub_sections(sections[1], 1)
 	}
 	if len(sections) > 2 {
-		third_section = get_sub_sections(sections[2])
+		third_section = get_sub_sections(sections[2], 0)
 	}
 	var ans = KeyEvent{Type: PRESS}
 	var keynum int

tools/tui/loop/key-encoding_test.go

@@ -0,0 +1,30 @@
+// License: GPLv3 Copyright: 2023, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package loop
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+var _ = fmt.Print
+
+func TestKeyEventFromCSI(t *testing.T) {
+
+	test_text := func(csi string, expected, alternate string) {
+		ev := KeyEventFromCSI(csi)
+		if ev == nil {
+			t.Fatalf("Failed to get parse %#v", csi)
+		}
+		if diff := cmp.Diff(expected, ev.Text); diff != "" {
+			t.Fatalf("Failed to get text from %#v:\n%s", csi, diff)
+		}
+		if diff := cmp.Diff(alternate, ev.AlternateKey); diff != "" {
+			t.Fatalf("Failed to get alternate from %#v:\n%s", csi, diff)
+		}
+	}
+	test_text("121;;121u", "y", "")
+	test_text("121::122;;121u", "y", "z")
+}