zapcore: add warning as Level

Some packages set their value for WarnLevel to "warning". For easier integration
add "warning" as accepted WarnLevel.

Example for a package that is using "warning":
https://github.com/sirupsen/logrus/blob/dd1b4c2e81afc5c255f216a722b012ed26be57df/logrus.go#L68

Signed-off-by: Florian Lehner <florian.lehner@elastic.co>

zapcore/level.go

@@ -183,7 +183,7 @@ func (l *Level) unmarshalText(text []byte) bool {
 		*l = DebugLevel
 	case "info", "INFO", "": // make the zero value useful
 		*l = InfoLevel
-	case "warn", "WARN":
+	case "warn", "warning", "WARN":
 		*l = WarnLevel
 	case "error", "ERROR":
 		*l = ErrorLevel

zapcore/level_test.go

@@ -57,13 +57,14 @@ func TestLevelText(t *testing.T) {
 		{"info", InfoLevel},
 		{"", InfoLevel}, // make the zero value useful
 		{"warn", WarnLevel},
+		{"warning", WarnLevel}, // compatibility handling for packages that emit "warning" instead of "warn"
 		{"error", ErrorLevel},
 		{"dpanic", DPanicLevel},
 		{"panic", PanicLevel},
 		{"fatal", FatalLevel},
 	}
 	for _, tt := range tests {
-		if tt.text != "" {
+		if tt.text != "" && tt.text != "warning" {
 			lvl := tt.level
 			marshaled, err := lvl.MarshalText()
 			assert.NoError(t, err, "Unexpected error marshaling level %v to text.", &lvl)