Validate that gui.spinner.frames must all have the same width

The spinner looks weird if they don't. While we're at it, validate that frames
must not be empty, which would have crashed with a division by zero.

pkg/config/user_config_validation.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"reflect"
@@ -8,6 +9,8 @@ import (
 	"strings"
 
 	"github.com/jesseduffield/lazygit/pkg/constants"
+	"github.com/jesseduffield/lazygit/pkg/utils"
+	"github.com/samber/lo"
 )
 
 func (config *UserConfig) Validate() error {
@@ -49,6 +52,22 @@ func (config *UserConfig) Validate() error {
 	if err := validateCustomCommands(config.CustomCommands); err != nil {
 		return err
 	}
+	if err := validateSpinner(config.Gui.Spinner); err != nil {
+		return err
+	}
+	return nil
+}
+
+func validateSpinner(spinner SpinnerConfig) error {
+	if len(spinner.Frames) == 0 {
+		return errors.New("gui.spinner.frames must not be empty.")
+	}
+	firstWidth := utils.StringWidth(spinner.Frames[0])
+	if lo.SomeBy(spinner.Frames, func(frame string) bool {
+		return utils.StringWidth(frame) != firstWidth
+	}) {
+		return errors.New("All gui.spinner.frames entries must have the same width.")
+	}
 	return nil
 }
 

pkg/config/user_config_validation_test.go

@@ -289,3 +289,33 @@ func TestUserConfigValidate_enums(t *testing.T) {
 		})
 	}
 }
+
+func TestUserConfigValidate_spinnerFrames(t *testing.T) {
+	scenarios := []struct {
+		name   string
+		frames []string
+		valid  bool
+	}{
+		{name: "empty", frames: []string{}, valid: false},
+		{name: "single frame", frames: []string{"|"}, valid: true},
+		{name: "all same width", frames: []string{"|", "/", "-", "\\"}, valid: true},
+		{name: "all same width, multi-char", frames: []string{".  ", ".. ", "..."}, valid: true},
+		{name: "all same width, wide runes", frames: []string{"⠋", "⠙", "⠹"}, valid: true},
+		{name: "differing widths", frames: []string{"|", "//"}, valid: false},
+		{name: "first differs from rest", frames: []string{"||", "/", "-"}, valid: false},
+	}
+
+	for _, s := range scenarios {
+		t.Run(s.name, func(t *testing.T) {
+			config := GetDefaultConfig()
+			config.Gui.Spinner.Frames = s.frames
+			err := config.Validate()
+
+			if s.valid {
+				assert.NoError(t, err)
+			} else {
+				assert.Error(t, err)
+			}
+		})
+	}
+}