[BCEL-379] Emit boolean literals for boolean ConstantValue fields

src/changes/changes.xml

@@ -61,6 +61,7 @@ The <action> type attribute can be add,update,fix,remove.
   <body>
     <release version="6.14.0" date="YYYY-MM-DD" description="This is a feature and maintenance release. Java 8 or later is required.">
       <!-- FIX -->
+      <action type="fix" issue="BCEL-379" due-to="Aryan Ganjoo">BCELifier now emits boolean literals for boolean ConstantValue fields so generated creator classes run.</action>
       <action                  type="fix" dev="ggregory" due-to="Gary Gregory">Use modern Mockito on Java 11+ (#528).</action>
       <action                  type="fix" dev="ggregory" due-to="Max Kammerer, akashchamp, Gary Gregory" issue="BCEL-280">MethodGen.setMaxLocals() should account for LocalVariableTable entries (#529).</action>
       <action                  type="fix" dev="ggregory" due-to="Gary Gregory">Fix constant pool module access test on Java 27 (#534).</action>

src/main/java/org/apache/bcel/util/BCELifier.java

@@ -281,7 +281,12 @@ public void visitField(final Field field) {
             if (field.getType() == Type.BYTE) {
                 printWriter.print("(byte)");
             }
-            printWriter.print(cv);
+            if (field.getType() == Type.BOOLEAN) {
+                // A boolean ConstantValue is stored as a CONSTANT_Integer, but FieldGen.setInitValue(int) rejects boolean fields.
+                printWriter.print(field.getConstantPool().getConstantInteger(cv.getConstantValueIndex()).getBytes() != 0);
+            } else {
+                printWriter.print(cv);
+            }
             if (field.getType() == Type.LONG) {
                 printWriter.print("L");
             }

src/test/java/BooleanConstants.java

@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+public class BooleanConstants {
+
+    public static final boolean ON = true;
+    public static final boolean OFF = false;
+}

src/test/java/org/apache/bcel/util/BCELifierTest.java

@@ -43,6 +43,7 @@
 import org.apache.bcel.generic.BinaryOpCreator;
 import org.apache.bcel.generic.ClassGen;
 import org.apache.bcel.generic.ConstantPoolGen;
+import org.apache.bcel.generic.FieldGen;
 import org.apache.bcel.generic.InstructionConst;
 import org.apache.bcel.generic.InstructionFactory;
 import org.apache.bcel.generic.InstructionList;
@@ -177,6 +178,31 @@ void testBinaryOp(final String exp) throws Exception {
         }
     }
 
+    @Test
+    void testBooleanConstantFieldInitValue() throws Exception {
+        // javac stores "static final boolean ON = true;" as a CONSTANT_Integer ConstantValue; the generated creator
+        // must call FieldGen.setInitValue(boolean), since setInitValue(int) throws for boolean fields.
+        final ClassGen cg = new ClassGen("Example", "java.lang.Object", "Example.java", Const.ACC_PUBLIC | Const.ACC_SUPER, new String[] {});
+        final ConstantPoolGen cp = cg.getConstantPool();
+        final FieldGen fg = new FieldGen(Const.ACC_PUBLIC | Const.ACC_STATIC | Const.ACC_FINAL, Type.BOOLEAN, "ON", cp);
+        fg.setInitValue(true);
+        cg.addField(fg.getField());
+
+        final ByteArrayOutputStream os = new ByteArrayOutputStream();
+        new BCELifier(cg.getJavaClass(), os).start();
+        final String source = new String(os.toByteArray(), StandardCharsets.UTF_8);
+
+        assertTrue(source.contains("field.setInitValue(true);"), source);
+        assertFalse(source.contains("field.setInitValue(1);"), source);
+
+        final ByteArrayOutputStream compiledClassOutput = new ByteArrayOutputStream();
+        new BCELifier(BCELifier.getJavaClass("BooleanConstants"), compiledClassOutput).start();
+        final String compiledClassSource = new String(compiledClassOutput.toByteArray(), StandardCharsets.UTF_8);
+        assertTrue(compiledClassSource.contains("field.setInitValue(true);"), compiledClassSource);
+        assertTrue(compiledClassSource.contains("field.setInitValue(false);"), compiledClassSource);
+        assertFalse(compiledClassSource.contains("field.setInitValue(0);"), compiledClassSource);
+    }
+
     @Test
     void testClassNameRejectedWhenNotJavaIdentifier() {
         // Class file names may contain characters the Java language forbids (JVMS 4.2.2 bans only . ; [ /).
@@ -297,7 +323,8 @@ void testHelloWorld() throws Exception {
         "org.apache.commons.lang.builder.ToStringBuilder.class",
         "org.apache.commons.lang.SerializationUtils.class",
         "org.apache.commons.lang.ArrayUtils.class",
-        "target/test-classes/Java4Example.class"
+        "target/test-classes/Java4Example.class",
+        "target/test-classes/BooleanConstants.class"
     // @formatter:on
     })
     void testJavapCompare(final String pathToClass) throws Exception {