Backport fix #2374

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -843,6 +843,10 @@ Cyril Martin ([email protected])
     does not provide "Type(Type(null))"
    (2.9.9)
 
-Daniil Barvitsky (dbarvitsky@github(
+Daniil Barvitsky (dbarvitsky@github)
   * Reported #2324: `StringCollectionDeserializer` fails with custom collection
    (2.9.9)
+
+Edgar Asatryan (nstdio@github)
+  * Reported #2374: `ObjectMapper. getRegisteredModuleIds()` throws NPE if no modules registered
+   (2.9.9.1)

release-notes/VERSION-2.x

@@ -8,6 +8,8 @@ Project: jackson-databind
 
 #2326: Block one more gadget type (CVE-2019-12384)
 #2341: Block one more gadget type (CVE-2019-12814)
+#2374: `ObjectMapper. getRegisteredModuleIds()` throws NPE if no modules registered
+ (reported by Edgar A)
 
 2.9.9 (16-May-2019)
 

src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java

@@ -962,7 +962,8 @@ public ObjectMapper registerModules(Iterable<? extends Module> modules)
      */
     public Set<Object> getRegisteredModuleIds()
     {
-        return Collections.unmodifiableSet(_registeredModuleTypes);
+        return (_registeredModuleTypes == null) ?
+                Collections.emptySet() : Collections.unmodifiableSet(_registeredModuleTypes);
     }
 
     /**

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

@@ -319,13 +319,18 @@ public void testGetRegisteredModules()
         AnotherSimpleModule mod2 = new AnotherSimpleModule("test2", Version.unknownVersion());
 
         ObjectMapper mapper = new ObjectMapper();
+
         mapper.registerModule(mod1);
         mapper.registerModule(mod2);
 
         Set<Object> registeredModuleIds = mapper.getRegisteredModuleIds();
         assertEquals(2, registeredModuleIds.size());
         assertTrue(registeredModuleIds.contains(mod1.getTypeId()));
         assertTrue(registeredModuleIds.contains(mod2.getTypeId()));
+
+        // 01-Jul-2019, [databind#2374]: verify empty list is fine
+        mapper = new ObjectMapper();
+        assertEquals(0, mapper.getRegisteredModuleIds().size());
     }
 
     /*