Fix #2309 (NPE for Enum.toString()) as suggested by Ben A

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -892,6 +892,10 @@ Pavel Chervakov (pacher@github)
   * Reported #2230: `WRITE_BIGDECIMAL_AS_PLAIN` is ignored if `@JsonFormat` is used
    (2.10.0)
 
+Ben Anderson (andersonbd1@github)
+  * Reported, suggested fix for #2309: READ_ENUMS_USING_TO_STRING doesn't support null values
+   (2.10.0)
+
 Manuel Hegner (manuel-hegner@github)
   * Suggested #2311: Unnecessary MultiView creation for property writers
    (2.10.0)

release-notes/VERSION-2.x

@@ -8,6 +8,8 @@ Project: jackson-databind
 
 #2237: Add "required" methods in `JsonNode`: `required(String | int)`,
   `requiredAt(JsonPointer)`
+#2309: READ_ENUMS_USING_TO_STRING doesn't support null values
+ (reported, fix suggested by Ben A)
 #2331: `JsonMappingException` through nested getter with generic wildcard return type
  (reported by sunchezz89@github)
 #2336: `MapDeserializer` can not merge `Map`s with polymorphic values

src/main/java/com/fasterxml/jackson/databind/util/CompactStringObjectMap.java

@@ -51,6 +51,11 @@ public static CompactStringObjectMap construct(Map<String,?> all)
         for (Map.Entry<String,?> entry : all.entrySet()) {
             String key = entry.getKey();
 
+            // 09-Sep-2019, tatu: [databind#2309] skip `null`s if any included
+            if (key == null) {
+                continue;
+            }
+            
             int slot = key.hashCode() & mask;
             int ix = slot+slot;
 

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

@@ -177,6 +177,25 @@ public void setupModule(SetupContext context) {
         }
     }
 
+    // for [databind#2309]
+    static enum Enum2309 {
+        NON_NULL("NON_NULL"),
+        NULL(null),
+        OTHER("OTHER")
+        ;
+
+        private String value;
+
+        private Enum2309(String value) {
+            this.value = value;
+        }
+
+        @Override
+        public String toString() {
+            return value;
+        }
+    }        
+
     /*
     /**********************************************************
     /* Test methods
@@ -285,12 +304,11 @@ public void testNumbersToEnums() throws Exception
 
     public void testEnumsWithIndex() throws Exception
     {
-        ObjectMapper m = jsonMapperBuilder()
-                .enable(SerializationFeature.WRITE_ENUMS_USING_INDEX)
-                .build();
-        String json = m.writeValueAsString(TestEnum.RULES);
+        String json = MAPPER.writer()
+                .with(SerializationFeature.WRITE_ENUMS_USING_INDEX)
+                .writeValueAsString(TestEnum.RULES);
         assertEquals(String.valueOf(TestEnum.RULES.ordinal()), json);
-        TestEnum result = m.readValue(json, TestEnum.class);
+        TestEnum result = MAPPER.readValue(json, TestEnum.class);
         assertSame(TestEnum.RULES, result);
     }
 
@@ -390,10 +408,10 @@ public void testGenericEnumDeserialization() throws Exception
 
     // [databind#381]
     public void testUnwrappedEnum() throws Exception {
-        final ObjectMapper mapper = jsonMapperBuilder()
-                .enable(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS)
-                .build();
-        assertEquals(TestEnum.JACKSON, mapper.readValue("[" + quote("JACKSON") + "]", TestEnum.class));
+        assertEquals(TestEnum.JACKSON,
+                MAPPER.readerFor(TestEnum.class)
+                    .with(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS)
+                    .readValue("[" + quote("JACKSON") + "]"));
     }
 
     public void testUnwrappedEnumException() throws Exception {
@@ -422,11 +440,10 @@ public void testIndexAsString() throws Exception
         assertSame(TestEnum.values()[1], en);
 
         // [databind#1690]: unless prevented
-        final ObjectMapper mapper = jsonMapperBuilder()
-                .disable(DeserializationFeature.ALLOW_COERCION_OF_SCALARS)
-                .build();
         try {
-            en = mapper.readValue(quote("1"), TestEnum.class);
+            en = MAPPER.readerFor(TestEnum.class)
+                    .without(DeserializationFeature.ALLOW_COERCION_OF_SCALARS)
+                    .readValue(quote("1"));
             fail("Should not pass");
         } catch (MismatchedInputException e) {
             verifyException(e, "Cannot deserialize value of type");
@@ -535,4 +552,13 @@ public void testExceptionFromCustomEnumKeyDeserializer() throws Exception {
             assertTrue(e.getMessage().contains("Undefined AnEnum"));
         }
     }
+
+    // [databind#2309]
+    public void testEnumToStringNull2309() throws Exception
+    {
+        Enum2309 value = MAPPER.readerFor(Enum2309.class)
+                .with(DeserializationFeature.READ_ENUMS_USING_TO_STRING)
+                .readValue(quote("NON_NULL"));
+        assertEquals(Enum2309.NON_NULL, value);
+    }
 }

src/test/java/com/fasterxml/jackson/databind/ser/TestEnumSerialization.java

@@ -108,6 +108,7 @@ static enum OK {
         OK(String key) { this.key = key; }
     }
 
+    @SuppressWarnings("rawtypes")
     static class LowerCasingEnumSerializer extends StdSerializer<Enum>
     {
         public LowerCasingEnumSerializer() { super(Enum.class); }