refactor: simplify implementation of getCaseExpression and setCaseExpression

src/main/java/spoon/support/reflect/code/CtCaseImpl.java

@@ -27,9 +27,6 @@
 public class CtCaseImpl<E> extends CtStatementImpl implements CtCase<E> {
 	private static final long serialVersionUID = 1L;
 
-	@MetamodelPropertyField(role = CtRole.EXPRESSION)
-	CtExpression<E> caseExpression;
-
 	@MetamodelPropertyField(role = CtRole.EXPRESSION)
 	List<CtExpression<E>> caseExpressions = emptyList();
 
@@ -46,7 +43,10 @@ public void accept(CtVisitor visitor) {
 
 	@Override
 	public CtExpression<E> getCaseExpression() {
-		return caseExpression;
+		if (caseExpressions.isEmpty()) {
+			return null;
+		}
+		return caseExpressions.get(0);
 	}
 
 	@Override
@@ -59,8 +59,9 @@ public <T extends CtCase<E>> T setCaseExpression(CtExpression<E> caseExpression)
 		if (caseExpression != null) {
 			caseExpression.setParent(this);
 		}
-		getFactory().getEnvironment().getModelChangeListener().onObjectUpdate(this, CtRole.CASE, caseExpression, this.caseExpression);
-		this.caseExpression = caseExpression;
+		this.caseExpressions = CtElementImpl.emptyList();
+		getFactory().getEnvironment().getModelChangeListener().onObjectUpdate(this, CtRole.CASE, caseExpression, this.caseExpressions);
+		addCaseExpression(caseExpression);
 		return (T) this;
 	}
 
@@ -89,9 +90,6 @@ public <T extends CtCase<E>> T addCaseExpression(CtExpression<E> caseExpression)
 			return (T) this;
 		}
 		this.ensureModifiableCaseExpressionsList();
-		if (getCaseExpression() == null) {
-			setCaseExpression(caseExpression);
-		}
 		getFactory().getEnvironment().getModelChangeListener().onObjectUpdate(this, CtRole.CASE, caseExpressions, this.caseExpressions);
 		caseExpression.setParent(this);
 		this.caseExpressions.add(caseExpression);

src/test/java/spoon/test/model/SwitchCaseTest.java

@@ -8,6 +8,8 @@
 
 package spoon.test.model;
 
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.jupiter.api.Assertions.assertAll;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
@@ -46,6 +48,7 @@
 import spoon.reflect.factory.Factory;
 import spoon.reflect.visitor.filter.TypeFilter;
 import spoon.support.compiler.VirtualFile;
+
 @DisplayName("Switchcase Tests")
 public class SwitchCaseTest {
 
@@ -365,4 +368,55 @@ public void test_addCaseAt_throwsIndexOutOfBoundsException_whenPositionIsOutOfBo
 			assertThrows(IndexOutOfBoundsException.class, () -> switchExpression.addCaseAt(3, onlyCase));
 		}
 	}
+
+	@Nested
+	class CaseExpressionInSwitchCasesBeforeJava12 {
+		@Test
+		public void test_getCaseExpression_shouldReturnTheFirstCaseExpression() {
+			// contract: `getCaseExpression` should return the first element in the list of case expressions stored in
+			// each instance of `CtCase`
+			Factory factory = new Launcher().getFactory();
+
+			CtCase<Integer> ctCase = factory.createCase();
+			CtExpression<Integer> first = factory.createLiteral(1);
+			CtExpression<Integer> second = factory.createLiteral(2);
+			CtExpression<Integer> third = factory.createLiteral(3);
+
+			ctCase.setCaseExpressions(Arrays.asList(first, second, third));
+
+			assertEquals(first, ctCase.getCaseExpression());
+		}
+
+		@Test
+		public void test_setCaseExpression_removeExistingCaseExpressionsAndInsertTheSpecified() {
+			// contract: `setCaseExpression` should clear the list of case expressions and insert the specified case
+			// expression
+			Factory factory = new Launcher().getFactory();
+
+			CtCase<Integer> ctCase = factory.createCase();
+			CtExpression<Integer> first = factory.createLiteral(1);
+			CtExpression<Integer> second = factory.createLiteral(2);
+			CtExpression<Integer> third = factory.createLiteral(3);
+			CtExpression<Integer> fourth = factory.createLiteral(4);
+			ctCase.setCaseExpressions(Arrays.asList(first, second, third));
+
+			ctCase.setCaseExpression(fourth);
+
+			assertEquals(1, ctCase.getCaseExpressions().size());
+			assertEquals(fourth, ctCase.getCaseExpression());
+		}
+
+		@Test
+		public void test_setCaseExpression_removeAllCaseExpressions() {
+			// contract: `setCaseExpression` should clear the list of case expressions when `null` is passed as
+			// argument
+			String code = "class A { public void f(int i) { switch(i) { case 1,2,3: break; } } }";
+			CtModel model = createModelFromString(code);
+			CtCase<?> ctCase = model.getElements(new TypeFilter<>(CtCase.class)).get(0);
+
+			ctCase.setCaseExpression(null);
+
+			assertThat(ctCase.getCaseExpressions().size(), equalTo(0));
+		}
+	}
 }