Make giving null to thrown() consistent with mock object creation (#1799

)

Co-authored-by: Leonard Brünings <[email protected]>

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

@@ -64,26 +64,25 @@ <T> T oldImpl(T expression) {
   }
 
   <T extends Throwable> T thrownImpl(String inferredName, Class<T> inferredType) {
-    if (inferredType == null) {
-      throw new InvalidSpecException("Thrown exception type cannot be inferred automatically. " +
-        "Please specify a type explicitly (e.g. 'thrown(MyException)').");
-    }
-
     return inferredType.cast(checkExceptionThrown(inferredType));
   }
 
   Throwable thrownImpl(String inferredName, Class<? extends Throwable> inferredType, Class<? extends Throwable> specifiedType) {
-    return checkExceptionThrown(specifiedType);
+    return checkExceptionThrown(specifiedType == null ? inferredType : specifiedType);
   }
 
   Throwable checkExceptionThrown(Class<? extends Throwable> exceptionType) {
-    Throwable actual = specificationContext.getThrownException();
+    if (exceptionType == null) {
+      throw new InvalidSpecException("Thrown exception type cannot be inferred automatically. " +
+        "Please specify a type explicitly (e.g. 'thrown(MyException)').");
+    }
 
     if (!Throwable.class.isAssignableFrom(exceptionType))
       throw new InvalidSpecException(
         "Invalid exception condition: '%s' is not a (subclass of) java.lang.Throwable"
       ).withArgs(exceptionType.getSimpleName());
 
+    Throwable actual = specificationContext.getThrownException();
     if (exceptionType.isInstance(actual)) return actual;
 
     throw new WrongExceptionThrownError(exceptionType, actual);

spock-specs/src/test/groovy/org/spockframework/smoke/condition/ExceptionConditions.groovy

@@ -168,6 +168,51 @@ thrown() == e
     e.message.startsWith("Exception conditions are only allowed as top-level statements")
   }
 
+  def "thrown condition with undeterminable exception type"() {
+    when:
+    runner.runFeatureBody """
+when:
+true
+
+then:
+$thrownInteraction
+    """
+
+    then:
+    InvalidSpecException e = thrown()
+    e.message == "Thrown exception type cannot be inferred automatically. Please specify a type explicitly (e.g. 'thrown(MyException)')."
+
+    where:
+    thrownInteraction << [
+      'thrown()',
+      'thrown(null)',
+      'def e = thrown(null)'
+    ]
+  }
+
+  def "thrown condition with explicit type null and inferred type"() {
+    when:
+    throw new Exception()
+
+    then:
+    Exception e = thrown(null)
+  }
+
+  def "thrown condition with explicit and inferred type"() {
+    when:
+    runner.runFeatureBody """
+when:
+throw new Exception()
+
+then:
+Exception e = thrown(IOException)
+    """
+
+    then:
+    WrongExceptionThrownError e = thrown()
+    e.message == "Expected exception of type 'java.io.IOException', but got 'java.lang.Exception'"
+  }
+
   @Issue("https://github.com/spockframework/spock/issues/260")
   @FailsWith(InvalidSpecException)
   def "(Java-style) exception condition must specify a type that is-a java.lang.Throwable"() {