Fix #2725

src/main/java/com/fasterxml/jackson/databind/deser/BasicDeserializerFactory.java

@@ -1702,7 +1702,8 @@ private KeyDeserializer _createEnumKeyDeserializer(DeserializationContext ctxt,
             }
         }
         EnumResolver enumRes = constructEnumResolver(enumClass, config, beanDesc.findJsonValueAccessor());
-        // May have @JsonCreator for static factory method:
+
+        // May have @JsonCreator for static factory method
         for (AnnotatedMethod factory : beanDesc.getFactoryMethods()) {
             if (_hasCreatorAnnotation(ctxt, factory)) {
                 int argCount = factory.getParameterCount();
@@ -1712,7 +1713,11 @@ private KeyDeserializer _createEnumKeyDeserializer(DeserializationContext ctxt,
                     if (returnType.isAssignableFrom(enumClass)) {
                         // note: mostly copied from 'EnumDeserializer.deserializerForCreator(...)'
                         if (factory.getRawParameterType(0) != String.class) {
-                            throw new IllegalArgumentException("Parameter #0 type for factory method ("+factory+") not suitable, must be java.lang.String");
+                            // [databind#2725]: Should not error out because (1) there may be good creator
+                            //   method and (2) this method may be valid for "regular" enum value deserialization
+                            // (leaving aside potential for multiple conflicting creators)
+//                            throw new IllegalArgumentException("Parameter #0 type for factory method ("+factory+") not suitable, must be java.lang.String");
+                            continue;
                         }
                         if (config.canOverrideAccessModifiers()) {
                             ClassUtil.checkAndFixAccess(factory.getMember(),

src/test/java/com/fasterxml/jackson/databind/deser/jdk/MapKeyDeserializationTest.java

@@ -1,11 +1,14 @@
 package com.fasterxml.jackson.databind.deser.jdk;
 
+import java.util.Collections;
 import java.util.Map;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonValue;
+
 import com.fasterxml.jackson.core.Base64Variants;
 import com.fasterxml.jackson.core.type.TypeReference;
+
 import com.fasterxml.jackson.databind.*;
 
 import org.junit.Assert;
@@ -37,6 +40,31 @@ public String toString() {
         }
     }
 
+    // [databind#2725]
+    enum TestEnum2725 {
+        FOO(1);
+
+        private final int i;
+
+        TestEnum2725(final int i) {
+            this.i = i;
+        }
+
+        @JsonValue
+        public int getI() {
+            return i;
+        }
+
+        @JsonCreator
+        public static TestEnum2725 getByIntegerId(final Integer id) {
+            return id == FOO.i ? FOO : null;
+        }
+
+        @JsonCreator
+        public static TestEnum2725 getByStringId(final String id) {
+            return Integer.parseInt(id) == FOO.i ? FOO : null;
+        }
+    }    
     /*
     /**********************************************************
     /* Test methods, wrapper keys
@@ -138,4 +166,16 @@ public void testByteArrayMapKeyDeserialization() throws Exception
         byte[] key = entry.getKey();
         Assert.assertArrayEquals(binary, key);
     }
+
+    // [databind#2725]
+    public void testEnumWithCreatorMapKeyDeserialization() throws Exception
+    {
+        final Map<TestEnum2725, String> input = Collections.singletonMap(TestEnum2725.FOO, "Hello");
+        final String json = MAPPER.writeValueAsString(input);
+        final Map<TestEnum2725, String> output = MAPPER.readValue(json,
+                new TypeReference<Map<TestEnum2725, String>>() { });
+
+        assertNotNull(output);
+        assertEquals(1, output.size());
+    }
 }