Make Validate.isAssignableFrom() check null inputs.

src/changes/changes.xml

@@ -75,6 +75,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action issue="LANG-1679" type="fix" dev="ggregory" due-to="clover">Improve performance of StringUtils.unwrap(String, String) #844.</action>
     <action issue="LANG-1675" type="fix" dev="ggregory" due-to="clover">Improve performance of StringUtils.join for primitives #812.</action>
     <action issue="LANG-1675" type="fix" dev="ggregory" due-to="Arturo Bernal">Fixed NPE getting Stack Trace if Throwable is null #733.</action>
+    <action                   type="fix" dev="ggregory" due-to="Gary Gregory, Arturo Bernal">Make Validate.isAssignableFrom() check null inputs.</action>
     <!-- ADD -->
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add EnumUtils.getEnumSystemProperty(...).</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add TriConsumer.</action>

src/main/java/org/apache/commons/lang3/Validate.java

@@ -1278,9 +1278,6 @@ public class Validate {
         }
     }
 
-    // isAssignableFrom
-    //---------------------------------------------------------------------------------
-
     /**
      * Validates that the argument can be converted to the specified class, if not, throws an exception.
      *
@@ -1299,9 +1296,9 @@ public class Validate {
      */
     public static void isAssignableFrom(final Class<?> superType, final Class<?> type) {
         // TODO when breaking BC, consider returning type
-        if (!superType.isAssignableFrom(type)) {
+        if (type == null || superType == null || !superType.isAssignableFrom(type)) {
-            throw new IllegalArgumentException(String.format(DEFAULT_IS_ASSIGNABLE_EX_MESSAGE, type == null ? "null" : type.getName(),
+            throw new IllegalArgumentException(
-                    superType.getName()));
+                String.format(DEFAULT_IS_ASSIGNABLE_EX_MESSAGE, ClassUtils.getName(type, "null type"), ClassUtils.getName(superType, "null type")));
         }
     }
 

src/test/java/org/apache/commons/lang3/ValidateTest.java

@@ -1849,7 +1849,34 @@ class ValidateTest {
 
                 assertEquals("Cannot assign a java.lang.String to a java.util.List", ex.getMessage());
             }
-        }
+
+            @Test
+            void shouldThrowIllegalArgumentExceptionWithNullSuperType() {
+                final IllegalArgumentException ex = assertThrows(
+                        IllegalArgumentException.class,
+                        () -> Validate.isAssignableFrom(null, String.class));
+
+                assertEquals("Cannot assign a java.lang.String to a null type", ex.getMessage());
+            }
+
+            @Test
+            void shouldThrowIllegalArgumentExceptionWithNullType() {
+                final IllegalArgumentException ex = assertThrows(
+                        IllegalArgumentException.class,
+                        () -> Validate.isAssignableFrom(List.class, null));
+
+                assertEquals("Cannot assign a null type to a java.util.List", ex.getMessage());
+            }
+
+            @Test
+            void shouldThrowIllegalArgumentExceptionWithNullTypes() {
+                final IllegalArgumentException ex = assertThrows(
+                        IllegalArgumentException.class,
+                        () -> Validate.isAssignableFrom(null, null));
+
+                assertEquals("Cannot assign a null type to a null type", ex.getMessage());
+            }
+}
 
         @Nested
         class WithMessage {