[grid] Silent fail on invalid log level (SeleniumHQ#15796)

* [grid] Silent fail on invalid log level

Fixing issue where providing an invalid log level to Grid will fail silently.

Since the logger is not yet configured a stacktrace with the exception is printed to console and we continue since the default log level is already configured.

Fixes SeleniumHQ#15790

* [grid] Silent fail on invalid log level

Adding link to logging levels as suggested by @diemol and formatting.

* [grid] Silent fail on invalid log level

Adding hardcoded log levels as suggested by review.

Author: Oxilod

java/src/org/openqa/selenium/grid/log/LoggingOptions.java

@@ -24,6 +24,7 @@
 import java.io.UnsupportedEncodingException;
 import java.util.Arrays;
 import java.util.Enumeration;
+import java.util.List;
 import java.util.Locale;
 import java.util.logging.Handler;
 import java.util.logging.Level;
@@ -49,6 +50,17 @@ public class LoggingOptions {
   private final Config config;
   private Level level = Level.INFO;
   public static final String DEFAULT_LOG_TIMESTAMP_FORMAT = "HH:mm:ss.SSS";
+  private static final List<Level> DEFAULT_LOG_LEVELS =
+      Arrays.asList(
+          Level.ALL,
+          Level.INFO,
+          Level.CONFIG,
+          Level.FINE,
+          Level.FINER,
+          Level.FINEST,
+          Level.OFF,
+          Level.SEVERE,
+          Level.WARNING);
 
   public LoggingOptions(Config config) {
     this.config = Require.nonNull("Config", config);
@@ -76,7 +88,15 @@ public void setLoggingLevel() {
     try {
       level = Level.parse(configLevel.toUpperCase(Locale.ROOT));
     } catch (IllegalArgumentException e) {
-      throw new ConfigException("Unable to determine log level from " + configLevel);
+      // Logger is not configured yet
+      new ConfigException(
+              "Unable to determine log level from "
+                  + configLevel
+                  + ". Using default "
+                  + DEFAULT_LOG_LEVEL
+                  + ". Available log levels are: "
+                  + DEFAULT_LOG_LEVELS)
+          .printStackTrace();
     }
   }