Minor reversion wrt #3110: limit changes to SimpleModule registration id handling

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/databind/module/SimpleModule.java

@@ -115,8 +115,8 @@ public class SimpleModule
     public SimpleModule() {
         // can't chain when making reference to 'this'
         // note: generate different name for direct instantiation, sub-classing
-        _name = (getClass() == SimpleModule.class) ?
-                "SimpleModule-"+System.identityHashCode(this)
+        _name = (getClass() == SimpleModule.class)
+                ? "SimpleModule-"+System.identityHashCode(this)
                 : getClass().getName();
         _version = Version.unknownVersion();
         // 07-Jun-2021, tatu: [databind#3110] Not passed explicitly so...
@@ -198,14 +198,22 @@ public SimpleModule(String name, Version version,
     @Override
     public Object getTypeId()
     {
-        // 07-Jun-2021, tatu: [databind#3110] Only return Type Id if name
-        //    was explicitly given
+        // 07-Jun-2021, tatu: [databind#3110] Return Type Id if name was
+        //    explicitly given
         if (_hasExplicitName) {
             return _name;
         }
-        // ...otherwise give no type id, even for sub-classes (sub-classes are
-        // welcome to override this method of course)
-        return null;
+        // Otherwise behavior same as with 2.12: no registration id for "throw-away"
+        // instances (to avoid bogus conflicts if user just instantiates SimpleModule)
+
+        // Note: actually... always returning `supet.getTypeId()` should be fine since
+        // that would return generated id? Let's do that actually.
+        if (getClass() == SimpleModule.class) {
+            return _name;
+        }
+        // And for what it is worth, this should usually do the same and we could
+        // in fact always just return `_name`. But leaving as-is for now.
+        return super.getTypeId();
     }
 
     /*

src/test/java/com/fasterxml/jackson/databind/module/SimpleModuleTest.java

@@ -334,14 +334,20 @@ public void testGetRegisteredModules()
         mapper = new ObjectMapper();
         assertEquals(0, mapper.getRegisteredModuleIds().size());
 
-        // 07-Jun-2021, tatu [databind#3110] Casual SimpleModules not returned
-        //     as registered
+        // 07-Jun-2021, tatu [databind#3110] Casual SimpleModules ARE returned
+        //    too!
         mapper = JsonMapper.builder()
                 .addModule(new SimpleModule())
                 .build();
-        assertEquals(0, mapper.getRegisteredModuleIds().size());
+        assertEquals(1, mapper.getRegisteredModuleIds().size());
+        Object id = mapper.getRegisteredModuleIds().iterator().next();
+        assertTrue(id instanceof String);
+        if (!id.toString().startsWith("SimpleModule-")) {
+            fail("SimpleModule registration id should start with 'SimpleModule-', does not: ["
+                    +id+"]");
+        }
 
-        // But named ones are
+        // And named ones retain their name
         mapper = JsonMapper.builder()
                 .addModule(new SimpleModule("VerySpecialModule"))
                 .build();