Fix #2632

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -1089,6 +1089,10 @@ Oleksandr Poslavskyi (alevskyi@github)
     property name if `MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES` is enabled
  (2.11.0)
 
+Simone D'Avico (simonedavico@github)
+  * Reported #2632: Failure to resolve generic type parameters on serialization
+ (2.11.0)
+ 
 Robin Roos (robinroos@github)
   * Contributed #2636: ObjectReader readValue lacks Class<T> argument
  (2.11.0)

release-notes/VERSION-2.x

@@ -42,6 +42,8 @@ Project: jackson-databind
  (reported by Bartosz B)
 #2592: `ObjectMapper.setSerializationInclusion()` is ignored for `JsonAnyGetter`
  (reported by Oleksii K)
+#2632: Failure to resolve generic type parameters on serialization
+ (reported by Simone D)
 #2636: ObjectReader readValue lacks Class<T> argument
  (contributed by Robin R)
 #2643: Change default textual serialization of `java.util.Date`/`Calendar`

src/main/java/com/fasterxml/jackson/databind/type/TypeFactory.java

@@ -449,7 +449,8 @@ public JavaType constructSpecializedType(JavaType baseType, Class<?> subclass,
                 break;
             }
             // (4) If all else fails, do the full traversal using placeholders
-            TypeBindings tb = _bindingsForSubtype(baseType, typeParamCount, subclass);
+            TypeBindings tb = _bindingsForSubtype(baseType, typeParamCount,
+                    subclass, relaxedCompatibilityCheck);
             newType = _fromClass(null, subclass, tb);
 
         } while (false);
@@ -460,7 +461,8 @@ public JavaType constructSpecializedType(JavaType baseType, Class<?> subclass,
         return newType;
     }
 
-    private TypeBindings _bindingsForSubtype(JavaType baseType, int typeParamCount, Class<?> subclass)
+    private TypeBindings _bindingsForSubtype(JavaType baseType, int typeParamCount,
+            Class<?> subclass, boolean relaxedCompatibilityCheck)
     {
         PlaceholderForType[] placeholders = new PlaceholderForType[typeParamCount];
         for (int i = 0; i < typeParamCount; ++i) {
@@ -479,8 +481,12 @@ private TypeBindings _bindingsForSubtype(JavaType baseType, int typeParamCount,
         // and traverse type hierarchies to both verify and to resolve placeholders
         String error = _resolveTypePlaceholders(baseType, baseWithPlaceholders);
         if (error != null) {
-            throw new IllegalArgumentException("Failed to specialize base type "+baseType.toCanonical()+" as "
-                    +subclass.getName()+", problem: "+error);
+            // 28-Mar-2020, tatu: As per [databind#2632], need to ignore the issue in
+            //   some cases. For now, just fully ignore; may need to refine in future
+            if (!relaxedCompatibilityCheck) {
+                throw new IllegalArgumentException("Failed to specialize base type "+baseType.toCanonical()+" as "
+                        +subclass.getName()+", problem: "+error);
+            }
         }
 
         final JavaType[] typeParams = new JavaType[typeParamCount];

src/test/java/com/fasterxml/jackson/databind/jsontype/SubTypeResolutionTest.java

@@ -129,17 +129,7 @@ public void testTypeSpecialization2034() throws Exception
     // [databind#2632]: fail to specialize type-erased
     public void testSpecializeIncompatibleRawType() throws Exception
     {
-        // 27-Feb-2020, tatu: First things first; incompatible typing should
-        //     cause reasonable exception
-        //  ... although since it's writing, perhaps should NOT fail at all?
-        String json;
-
-        try {
-            json = MAPPER.writeValueAsString(new Foo());
-            assertNotNull(json);
-            fail("Should not (yet?) pass");
-        } catch (JsonMappingException e) {
-                verifyException(e, "Failed to specialize base type ");
-        }
+        String json = MAPPER.writeValueAsString(new Foo());
+        assertNotNull(json);
     }
 }