sort list of languages

internal/app/languages.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"io"
 	"reflect"
+	"slices"
+	"strings"
 
 	gherkin "github.com/cucumber/gherkin/go/v28"
 	"github.com/hedhyw/semerr/pkg/v1/semerr"
@@ -15,6 +17,10 @@ func runListFeatureLanguages(out io.Writer) error {
 		return fmt.Errorf("getting feature languages: %w", err)
 	}
 
+	slices.SortFunc(languages, func(a, b *gherkin.Dialect) int {
+		return strings.Compare(a.Language, b.Language)
+	})
+
 	for _, lang := range languages {
 		fmt.Fprintf(out, "%s\t%s\t%s\n", lang.Language, lang.Name, lang.Native)
 	}

internal/app/languages_private_test.go

@@ -0,0 +1,31 @@
+package app
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRunListFeatureLanguages(t *testing.T) {
+	t.Parallel()
+
+	t.Run("it produces a stable output", func(t *testing.T) {
+		t.Parallel()
+
+		var buf bytes.Buffer
+
+		require.NoError(t, runListFeatureLanguages(&buf))
+
+		out1 := buf.String()
+
+		buf.Reset()
+
+		require.NoError(t, runListFeatureLanguages(&buf))
+
+		out2 := buf.String()
+
+		assert.Equal(t, out1, out2)
+	})
+}