Fix #550

src/main/java/com/beust/jcommander/converters/EnumConverter.java

@@ -27,16 +27,14 @@ public EnumConverter(String optionName, Class<T> clazz) {
 
   @Override
   public T convert(String value) {
-    try {
-      try {
-        return Enum.valueOf(clazz, value);
-      } catch (IllegalArgumentException e) {
-        return Enum.valueOf(clazz, value.toUpperCase());
+    for (T constant : EnumSet.allOf(clazz)) {
+      // the toString method may be overridden, causing what is printed (or what user types) is different from it's declared name
+      if (constant.name().equals(value) || constant.name().equals(value.toUpperCase())
+          || constant.toString().equals(value) || constant.toString().equals(value.toUpperCase())) {
+        return constant;
       }
-    } catch (Exception e) {
-      throw new ParameterException("Invalid value for " + optionName + " parameter. Allowed values:" +
-          EnumSet.allOf(clazz));
-
     }
+    throw new ParameterException("Invalid value for " + optionName + " parameter. Allowed values:" +
+            EnumSet.allOf(clazz));
   }
 }

src/test/java/com/beust/jcommander/converters/EnumConverterTest.java

@@ -0,0 +1,69 @@
+/**
+ * Copyright (C) 2024 the original author or authors.
+ * See the notice.md file distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.beust.jcommander.converters;
+
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+@Test
+public class EnumConverterTest {
+    private static final EnumConverter<Season> SEASON_ENUM_CONVERTER = new EnumConverter<>("", Season.class);
+
+    private static final EnumConverter<Resolution> RESOLUTION_ENUM_CONVERTER = new EnumConverter<>("", Resolution.class);
+
+    @Test
+    public void testMatch() {
+        Assert.assertEquals(Season.AUTUMN, SEASON_ENUM_CONVERTER.convert("AUTUMN"));
+    }
+
+    @Test
+    public void testMatchLowerCase() {
+        Assert.assertEquals(Season.AUTUMN, SEASON_ENUM_CONVERTER.convert("autumn"));
+    }
+
+    @Test
+    public void testMatchWithToString() {
+        Assert.assertEquals(Resolution.R_4K, RESOLUTION_ENUM_CONVERTER.convert("4k"));
+        Assert.assertEquals(Resolution.R_1080P, RESOLUTION_ENUM_CONVERTER.convert("1080P"));
+    }
+
+    @Test
+    public void testNoMatch() {
+        Assert.assertThrows(() -> SEASON_ENUM_CONVERTER.convert("XXX"));
+        Assert.assertThrows(() -> RESOLUTION_ENUM_CONVERTER.convert("XXX"));
+    }
+
+    private enum Season {
+        SPRING,
+        SUMMER,
+        AUTUMN,
+        WINTER
+    }
+
+    private enum Resolution {
+        R_4K, // can not start with a number
+        R_1080P,
+        R_480P;
+
+        @Override
+        public String toString() {
+            return name().substring(2); // removes the prefix for user-friendly reading
+        }
+    }
+}