Added special handling for Collection.contains(Object) throwing NullPointerException because the collection does not permit null elements.

Author: cowwoc

docs/Changelog.md

@@ -7,6 +7,8 @@ See https://github.com/cowwoc/requirements.java/commits/master for a full list.
 * Improvements
     * When referencing to a variable number of elements, always use the plural form of a type (e.g.
       `actual must contain X entries` even if `X` is one).
+    * Added special handling for `Collection.contains(Object)` throwing `NullPointerException` because the
+      collection does not permit null elements.
 
 ## Version 10.0 - 2024/10/31
 

java/src/main/java/com/github/cowwoc/requirements10/java/internal/validator/AbstractCollectionValidator.java

@@ -95,9 +95,26 @@ public S contains(E expected, String name)
 		return containsImpl(expected, name);
 	}
 
+	@SuppressWarnings("PMD.AvoidCatchingNPE")
 	private S containsImpl(E expected, String name)
 	{
-		if (value.validationFailed(v -> v.contains(expected)))
+		if (value.validationFailed(v ->
+		{
+			try
+			{
+				return v.contains(expected);
+			}
+			catch (NullPointerException e)
+			{
+				if (expected == null)
+				{
+					// The specified element is null, and this collection does not permit null elements
+					assert (v != null);
+					return false;
+				}
+				throw e;
+			}
+		}))
 		{
 			failOnNull();
 			addIllegalArgumentException(CollectionMessages.containsFailed(this, name, expected).toString());
@@ -119,9 +136,22 @@ public S doesNotContain(E unwanted, String name)
 		return doesNotContainImpl(unwanted, name);
 	}
 
+	@SuppressWarnings("PMD.AvoidCatchingNPE")
 	private S doesNotContainImpl(E unwanted, String name)
 	{
-		if (value.validationFailed(v -> !v.contains(unwanted)))
+		if (value.validationFailed(v ->
+		{
+			try
+			{
+				return !v.contains(unwanted);
+			}
+			catch (NullPointerException e)
+			{
+				// The specified element is null, and this collection does not permit null elements
+				assert (v != null);
+				return true;
+			}
+		}))
 		{
 			failOnNull();
 			addIllegalArgumentException(

test/src/test/java/com/github/cowwoc/requirements10/test/java/CollectionTest.java

@@ -13,9 +13,7 @@
 
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 
 import static com.github.cowwoc.requirements10.java.TerminalEncoding.NONE;
 
@@ -102,6 +100,20 @@ public void contains_False()
 		}
 	}
 
+	@Test
+	public void containsNull_collectionDoesNotPermitNull()
+	{
+		try (ApplicationScope scope = new TestApplicationScope(NONE))
+		{
+			Collection<String> actual = List.of("element");
+			List<String> expectedMessages = List.of("\"actual\" must contain null");
+			List<String> actualMessages = new TestValidatorsImpl(scope).checkIf(actual, "actual").
+				contains(null).elseGetFailures().getMessages();
+			new TestValidatorsImpl(scope).requireThat(actualMessages, "actualMessages").
+				isEqualTo(expectedMessages);
+		}
+	}
+
 	@Test
 	public void containsVariable()
 	{
@@ -331,6 +343,17 @@ public void doesNotContain_False()
 		}
 	}
 
+	@Test
+	public void doesNotContainNull_collectionDoesNotPermitNull()
+	{
+		try (ApplicationScope scope = new TestApplicationScope(NONE))
+		{
+			Collection<String> actual = List.of("element");
+			new TestValidatorsImpl(scope).requireThat(actual, "actual").
+				doesNotContain(null);
+		}
+	}
+
 	@Test
 	public void doesNotContainVariable()
 	{