Adds support for `LC_MESSAGES` and `LC_ALL`

pkg/kubectl/util/i18n/i18n.go

@@ -50,9 +50,18 @@ var knownTranslations = map[string][]string{
 }
 
 func loadSystemLanguage() string {
-	langStr := os.Getenv("LANG")
+	// Implements the following locale priority order: LC_ALL, LC_MESSAGES, LANG
+	// Similarly to: https://www.gnu.org/software/gettext/manual/html_node/Locale-Environment-Variables.html
+	langStr := os.Getenv("LC_ALL")
 	if langStr == "" {
-		glog.V(3).Infof("Couldn't find the LANG environment variable, defaulting to en_US")
+		langStr = os.Getenv("LC_MESSAGES")
+	}
+	if langStr == "" {
+		langStr = os.Getenv("LANG")
+	}
+
+	if langStr == "" {
+		glog.V(3).Infof("Couldn't find the LC_ALL, LC_MESSAGES or LANG environment variables, defaulting to en_US")
 		return "default"
 	}
 	pieces := strings.Split(langStr, ".")

pkg/kubectl/util/i18n/i18n_test.go

@@ -21,6 +21,8 @@ import (
 	"testing"
 )
 
+var knownTestLocale = "en_US.UTF-8"
+
 func TestTranslation(t *testing.T) {
 	err := LoadTranslations("test", func() string { return "default" })
 	if err != nil {
@@ -50,15 +52,106 @@ func TestTranslationPlural(t *testing.T) {
 	}
 }
 
-func TestTranslationEnUSEnv(t *testing.T) {
-	os.Setenv("LANG", "en_US.UTF-8")
+func TestTranslationUsingEnvVar(t *testing.T) {
+	// We must backup and restore env vars before setting test values in tests
+	// othervise we are risking to break other tests/test cases
+	// which rely on the same env vars
+	envVarsToBackup := []string{"LC_MESSAGES", "LANG", "LC_ALL"}
+	expectedStrEnUSLocale := "baz"
+	expectedStrFallback := "foo"
+
+	testCases := []struct {
+		name        string
+		setenvFn    func()
+		expectedStr string
+	}{
+		{
+			name:        "Only LC_ALL is set",
+			setenvFn:    func() { os.Setenv("LC_ALL", knownTestLocale) },
+			expectedStr: expectedStrEnUSLocale,
+		},
+		{
+			name:        "Only LC_MESSAGES is set",
+			setenvFn:    func() { os.Setenv("LC_MESSAGES", knownTestLocale) },
+			expectedStr: expectedStrEnUSLocale,
+		},
+		{
+			name:        "Only LANG",
+			setenvFn:    func() { os.Setenv("LANG", knownTestLocale) },
+			expectedStr: expectedStrEnUSLocale,
+		},
+		{
+			name: "LC_MESSAGES overrides LANG",
+			setenvFn: func() {
+				os.Setenv("LANG", "be_BY.UTF-8") // Unknown locale
+				os.Setenv("LC_MESSAGES", knownTestLocale)
+			},
+			expectedStr: expectedStrEnUSLocale,
+		},
+		{
+			name: "LC_ALL overrides LANG",
+			setenvFn: func() {
+				os.Setenv("LANG", "be_BY.UTF-8") // Unknown locale
+				os.Setenv("LC_ALL", knownTestLocale)
+			},
+			expectedStr: expectedStrEnUSLocale,
+		},
+		{
+			name: "LC_ALL overrides LC_MESSAGES",
+			setenvFn: func() {
+				os.Setenv("LC_MESSAGES", "be_BY.UTF-8") // Unknown locale
+				os.Setenv("LC_ALL", knownTestLocale)
+			},
+			expectedStr: expectedStrEnUSLocale,
+		},
+		{
+			name:        "Unknown locale in LANG",
+			setenvFn:    func() { os.Setenv("LANG", "be_BY.UTF-8") },
+			expectedStr: expectedStrFallback,
+		},
+		{
+			name:        "Unknown locale in LC_MESSAGES",
+			setenvFn:    func() { os.Setenv("LC_MESSAGES", "be_BY.UTF-8") },
+			expectedStr: expectedStrFallback,
+		},
+		{
+			name:        "Unknown locale in LC_ALL",
+			setenvFn:    func() { os.Setenv("LC_ALL", "be_BY.UTF-8") },
+			expectedStr: expectedStrFallback,
+		},
+		{
+			name:        "Invalid env var",
+			setenvFn:    func() { os.Setenv("LC_MESSAGES", "fake.locale.UTF-8") },
+			expectedStr: expectedStrFallback,
+		},
+		{
+			name:        "No env vars",
+			setenvFn:    func() {},
+			expectedStr: expectedStrFallback,
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.name, func(t *testing.T) {
+			for _, envVar := range envVarsToBackup {
+				if envVarValue := os.Getenv(envVar); envVarValue != "" {
+					os.Unsetenv(envVar)
+					// Restore env var at the end
+					defer func() { os.Setenv(envVar, envVarValue) }()
+				}
+			}
+
+			test.setenvFn()
+
 			err := LoadTranslations("test", nil)
 			if err != nil {
 				t.Errorf("Unexpected error: %v", err)
 			}
 
 			result := T("test_string")
-	if result != "baz" {
-		t.Errorf("expected: %s, saw: %s", "baz", result)
+			if result != test.expectedStr {
+				t.Errorf("expected: %s, saw: %s", test.expectedStr, result)
+			}
+		})
 	}
 }