Fix SpyStatic() with an interaction closure throws NullPointerException

The usage of SpyStaticImpl(Type){

}
had thrown an NullPointerException,
because the closure got converted into IMockMakerSettings.

Author: AndreasTu

docs/release_notes.adoc

@@ -112,6 +112,7 @@ spockPull:2112[]
 * Fix filter blocks with shared fields and derived data variables spockPull:2088[]
 * Fix combined labels with comments being ignored spockPull:2121[]
 * Fix boxed Boolean `is` getter methods not properly mocked in Groovy <= 3 spockIssue:2131[]
+* Fix `SpyStatic()` with an interaction closure throws NullPointerException spockPull:xxx[]
 
 Thanks to all the contributors to this release: Andreas Turban, Björn Kautler, Christoph Loy, Marcin Zajączkowski, Pavlo Shevchenko
 

spock-core/src/main/java/org/spockframework/mock/runtime/MockMakerRegistry.java

@@ -16,18 +16,21 @@
 
 package org.spockframework.mock.runtime;
 
+import groovy.lang.Closure;
 import org.spockframework.mock.CannotCreateMockException;
 import org.spockframework.mock.IMockObject;
 import org.spockframework.mock.ISpockMockObject;
 import org.spockframework.mock.runtime.IMockMaker.IStaticMock;
 import org.spockframework.mock.runtime.IMockMaker.MockMakerCapability;
+import org.spockframework.runtime.GroovyRuntimeUtil;
 import org.spockframework.util.InternalSpockError;
 import org.spockframework.util.Nullable;
 import org.spockframework.util.ThreadSafe;
 import spock.mock.IMockMakerSettings;
 import spock.mock.MockMakerId;
 
 import java.lang.reflect.Modifier;
+import java.lang.reflect.Proxy;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
@@ -145,6 +148,10 @@ public <T> T makeMockInternal(IMockCreationSettings settings, BiFunction<IMockMa
       MockMakerId mockMakerId = mockMakerSettings.getMockMakerId();
       IMockMaker mockMaker = makerMap.get(mockMakerId);
       if (mockMaker == null) {
+        if (mockMakerId == null && (mockMakerSettings instanceof Proxy || mockMakerSettings instanceof Closure)) {
+          throw new CannotCreateMockException(settings.getMockType(), " because the MockMakerSettings returned the invalid ID 'null'. Please check that a closure did not get accidentally casted to IMockMakerSettings."
+            + " The settings object was '" + GroovyRuntimeUtil.toString(mockMakerSettings) + "'.");
+        }
         throw new CannotCreateMockException(settings.getMockType(), " because MockMaker with ID '" + mockMakerId + "' does not exist.");
       }
       verifyIsMockable(mockMaker, settings);

spock-core/src/main/java/org/spockframework/runtime/SpecInternals.java

@@ -333,14 +333,18 @@ private static <T> T createMockImpl(Specification specification, String inferred
   }
 
   public static void SpyStaticImpl(Specification specification, String inferredName, Type inferredType, Class<?> specifiedType) {
-    createStaticMockImpl(specification, MockNature.SPY, specifiedType, null);
+    createStaticMockImpl(specification, MockNature.SPY, specifiedType, null, null);
+  }
+
+  public static void SpyStaticImpl(Specification specification, String inferredName, Type inferredType, Class<?> specifiedType, Closure<?> closure) {
+    createStaticMockImpl(specification, MockNature.SPY, specifiedType, null, closure);
   }
 
   public static void SpyStaticImpl(Specification specification, String inferredName, Type inferredType, Class<?> specifiedType, IMockMakerSettings mockMakerSettings) {
-    createStaticMockImpl(specification, MockNature.SPY, specifiedType, mockMakerSettings);
+    createStaticMockImpl(specification, MockNature.SPY, specifiedType, mockMakerSettings, null);
   }
 
-  private static void createStaticMockImpl(Specification specification, MockNature nature, Class<?> specifiedType, @Nullable IMockMakerSettings mockMakerSettings) {
+  private static void createStaticMockImpl(Specification specification, MockNature nature, Class<?> specifiedType, @Nullable IMockMakerSettings mockMakerSettings, @Nullable Closure<?> closure) {
     if (specifiedType == null) {
       throw new InvalidSpecException("The type must not be null.");
     }
@@ -349,5 +353,8 @@ private static void createStaticMockImpl(Specification specification, MockNature
       options = Collections.singletonMap("mockMaker", mockMakerSettings);
     }
     createStaticMock(specification, specifiedType, nature, options);
+    if (closure != null) {
+      GroovyRuntimeUtil.invokeClosure(closure, specifiedType);
+    }
   }
 }

spock-core/src/main/java/spock/mock/IMockMakerSettings.java

@@ -16,6 +16,7 @@
  * <p>If you provide a method, you can define your settings in a typesafe manner for the user,
  * e.g. with a {@link Closure} parameter to configure the mock.
  *
+ * @author Andreas Turban
  * @since 2.4
  */
 @Beta
@@ -41,5 +42,8 @@ public String toString() {
     };
   }
 
+  /**
+   * @return the {@link MockMakerId} to use, must not be {@code null}.
+   */
   MockMakerId getMockMakerId();
 }

spock-core/src/main/java/spock/mock/MockingApi.java

@@ -1643,6 +1643,32 @@ public <T> void SpyStatic(Class<T> type) {
     throw invalidMockCreation();
   }
 
+  /**
+   * Creates a thread-local spy for all static methods of the passed type.
+   * <p>
+   * Example:
+   *
+   * <pre>
+   *   SpyStatic(Person){
+   *      Person.staticMethod() >> "result"
+   *   }
+   * </pre>
+   *
+   * <p>Please use the class name as a prefix, instead of relying on {@code it} from Groovy.</p>
+   *
+   * <p>If you want to activate the static mocks on a different {@code Thread},
+   * please call {@link #runWithThreadAwareMocks(Runnable)} on the different {@code Thread}.
+   *
+   * @param type         the type of which the static methods shall be spied
+   * @param interactions a description of the static spy's interactions
+   */
+  @Beta
+  public <T> void SpyStatic(Class<T> type, Closure<?> interactions //Note: We can't specify here @ClosureParams or @DelegatesTo because there is no syntax to express that it means the Class object
+  ) {
+
+    throw invalidMockCreation();
+  }
+
   /**
    * Creates a thread-local spy for all static methods of the passed type.
    * <p>
@@ -1663,7 +1689,6 @@ public <T> void SpyStatic(Class<T> type, IMockMakerSettings mockMakerSettings) {
     throw invalidMockCreation();
   }
 
-
   /**
    * Runs the code with the thread-aware mocks activated on the current {@link Thread}.
    *

spock-specs/src/test/groovy/org/spockframework/mock/runtime/mockito/MockitoStaticMocksSpec.groovy

@@ -25,6 +25,7 @@ import org.spockframework.runtime.InvalidSpecException
 import spock.lang.Issue
 import spock.lang.Shared
 import spock.lang.Specification
+import spock.mock.IMockMakerSettings
 import spock.mock.MockMakers
 
 import java.util.concurrent.Callable
@@ -491,6 +492,64 @@ class MockitoStaticMocksSpec extends Specification {
     !StaticClass.staticVarargsMethod("test2")
   }
 
+  def "SpyStatic with closure shall not lead an exception"() {
+    when:
+    SpyStatic(StaticClass) {
+
+    }
+
+    then:
+    noExceptionThrown()
+  }
+
+  def "SpyStatic with closure can specify interactions"() {
+    given:
+    SpyStatic(StaticClass) {
+      StaticClass.staticVarargsMethod("test") >> true
+    }
+
+    expect:
+    StaticClass.staticVarargsMethod("test")
+  }
+
+  def "SpyStatic with closure could use it instead of ClassName"() {
+    given:
+    SpyStatic(StaticClass) {
+      //Note: This does not have code completion support.
+      it.staticVarargsMethod("test") >> true
+    }
+
+    expect:
+    StaticClass.staticVarargsMethod("test")
+  }
+
+  def "SpyStatic with closure could use no prefix instead of ClassName"() {
+    given:
+    SpyStatic(StaticClass) {
+      //Note: This does not have code completion support.
+      staticVarargsMethod("test") >> true
+    }
+
+    expect:
+    StaticClass.staticVarargsMethod("test")
+  }
+
+  /**
+   * The IMockMakerSettings has only a single method, so it could be converted from a Groovy closure automatically.
+   * This shall check that the API produces a nice error to the user in such cases.
+   */
+  def "SpyStatic with closure casted as IMockMakerSettings shall produce nice error message"() {
+    when:
+    SpyStatic(StaticClass, {
+
+    } as IMockMakerSettings)
+
+    then:
+    def ex = thrown(CannotCreateMockException)
+    ex.message.startsWith(
+      "Cannot create mock for class $StaticClass.name because the MockMakerSettings returned the invalid ID 'null'. Please check that a closure did not get accidentally casted to IMockMakerSettings. The settings object was ")
+  }
+
   static class StaticClass {
 
     String instanceMethod() {

spock-specs/src/test/groovy/spock/mock/MockingApiInvalidUsageSpec.groovy

@@ -95,6 +95,7 @@ class MockingApiInvalidUsageSpec extends Specification {
     "GroovySpy"  | [CLOSURE]
 
     "SpyStatic"  | [Runnable]
-    "SpyStatic" | [Runnable, MockMakers.mockito]
+    "SpyStatic"  | [Runnable, CLOSURE]
+    "SpyStatic"  | [Runnable, MockMakers.mockito]
   }
 }