Groovy example source code file (AssertionWriter.java)

This example Groovy source code file (AssertionWriter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Groovy tags/keywords

assertiontracker, assertiontracker, binaryexpression, booleanexpression, booleanexpression, invokevirtual, invokevirtual, label, label, methodvisitor, operandstack, string, util, v, variableexpression

The Groovy AssertionWriter.java source code

/*
 * Copyright 2003-2010 the original author or authors.
 *
 * Licensed 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
 *
 *     http://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.
 */
package org.codehaus.groovy.classgen.asm;

import java.util.ArrayList;
import java.util.List;

import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.expr.BinaryExpression;
import org.codehaus.groovy.ast.expr.BooleanExpression;
import org.codehaus.groovy.ast.expr.ConstantExpression;
import org.codehaus.groovy.ast.expr.Expression;
import org.codehaus.groovy.ast.expr.VariableExpression;
import org.codehaus.groovy.ast.stmt.AssertStatement;
import org.codehaus.groovy.control.Janitor;
import org.codehaus.groovy.runtime.ScriptBytecodeAdapter;
import org.codehaus.groovy.runtime.powerassert.SourceText;
import org.codehaus.groovy.runtime.powerassert.SourceTextNotAvailableException;
import org.codehaus.groovy.syntax.Token;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;

import static org.objectweb.asm.Opcodes.*;

public class AssertionWriter {
    // assert
    private static final MethodCaller assertFailedMethod = MethodCaller.newStatic(ScriptBytecodeAdapter.class, "assertFailed");
    
    private static class AssertionTracker {
        int recorderIndex;
        SourceText sourceText;
    }

    private WriterController controller;
    private AssertionTracker assertionTracker;
    private AssertionTracker disabledTracker;
    
    public AssertionWriter(WriterController wc) {
        this.controller = wc;
    }
    
    public void writeAssertStatement(AssertStatement statement) {
        MethodVisitor mv = controller.getMethodVisitor();
        OperandStack operandStack = controller.getOperandStack();
        
        boolean rewriteAssert = true;
        // don't rewrite assertions with message
        rewriteAssert = statement.getMessageExpression() == ConstantExpression.NULL;
        AssertionTracker oldTracker = assertionTracker;
        Janitor janitor = new Janitor();
        final Label tryStart = new Label();
        if (rewriteAssert){
            assertionTracker = new AssertionTracker();
            try {
                // because source position seems to be more reliable for statements
                // than for expressions, we get the source text for the whole statement
                assertionTracker.sourceText = new SourceText(statement, controller.getSourceUnit(), janitor);
                mv.visitTypeInsn(NEW, "org/codehaus/groovy/runtime/powerassert/ValueRecorder");
                mv.visitInsn(DUP);
                mv.visitMethodInsn(INVOKESPECIAL, "org/codehaus/groovy/runtime/powerassert/ValueRecorder", "<init>", "()V");
                //TODO: maybe use more specialized type here
                controller.getOperandStack().push(ClassHelper.OBJECT_TYPE);
                assertionTracker.recorderIndex = controller.getCompileStack().defineTemporaryVariable("recorder", true);
                mv.visitLabel(tryStart);
            } catch (SourceTextNotAvailableException e) {
                // don't rewrite assertions w/o source text
                rewriteAssert = false;
            }
        }
        
        statement.getBooleanExpression().visit(controller.getAcg());

        Label exceptionThrower = operandStack.jump(IFEQ);

        // do nothing, but clear the value recorder
        if (rewriteAssert) {
            //clean up assertion recorder
            mv.visitVarInsn(ALOAD, assertionTracker.recorderIndex);
            mv.visitMethodInsn(
                    INVOKEVIRTUAL, 
                    "org/codehaus/groovy/runtime/powerassert/ValueRecorder",
                    "clear", 
                    "()V");
        }
        Label afterAssert = new Label();
        mv.visitJumpInsn(GOTO, afterAssert);
        mv.visitLabel(exceptionThrower);
        
        if (rewriteAssert) {
            mv.visitLdcInsn(assertionTracker.sourceText.getNormalizedText());
            mv.visitVarInsn(ALOAD, assertionTracker.recorderIndex);
            mv.visitMethodInsn(
                    INVOKESTATIC, 
                    "org/codehaus/groovy/runtime/powerassert/AssertionRenderer",
                    "render", 
                    "(Ljava/lang/String;Lorg/codehaus/groovy/runtime/powerassert/ValueRecorder;)Ljava/lang/String;"
            );
        } else {
            writeSourcelessAssertText(statement);
        }
        operandStack.push(ClassHelper.STRING_TYPE);
        AssertionTracker savedTracker = assertionTracker;
        assertionTracker = null;
        
        // now the optional exception expression
        statement.getMessageExpression().visit(controller.getAcg());
        operandStack.box();
        assertFailedMethod.call(mv);
        operandStack.remove(2); // assertFailed called static with 2 arguments 
        
        if (rewriteAssert) {
            final Label tryEnd = new Label();
            mv.visitLabel(tryEnd);
            mv.visitJumpInsn(GOTO, afterAssert);
            // finally block to clean assertion recorder
            final Label catchAny = new Label();
            mv.visitLabel(catchAny);
            mv.visitVarInsn(ALOAD, savedTracker.recorderIndex);
            mv.visitMethodInsn(
                    INVOKEVIRTUAL, 
                    "org/codehaus/groovy/runtime/powerassert/ValueRecorder",
                    "clear", 
                    "()V");
            mv.visitInsn(ATHROW);
            // add catch any block to exception table
            controller.getCompileStack().addExceptionBlock(tryStart, tryEnd, catchAny, null);
        }
        
        mv.visitLabel(afterAssert);
        if (rewriteAssert) {
            controller.getCompileStack().removeVar(savedTracker.recorderIndex);
        }
        assertionTracker = oldTracker;
        // close possibly open file handles from getting a sample for 
        // power asserts
        janitor.cleanup();
    }
    
    private void writeSourcelessAssertText(AssertStatement statement) {
        MethodVisitor mv = controller.getMethodVisitor();
        OperandStack operandStack = controller.getOperandStack();
        
        BooleanExpression booleanExpression = statement.getBooleanExpression();
        // push expression string onto stack
        String expressionText = booleanExpression.getText();
        List<String> list = new ArrayList();
        addVariableNames(booleanExpression, list);
        if (list.isEmpty()) {
            mv.visitLdcInsn(expressionText);
        } else {
            boolean first = true;

            // let's create a new expression
            mv.visitTypeInsn(NEW, "java/lang/StringBuffer");
            mv.visitInsn(DUP);
            mv.visitLdcInsn(expressionText + ". Values: ");
            mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuffer", "<init>", "(Ljava/lang/String;)V");
            //TODO: maybe use more special type StringBuffer here
            operandStack.push(ClassHelper.OBJECT_TYPE);
            int tempIndex = controller.getCompileStack().defineTemporaryVariable("assert", true);

            for (String name : list) {
                String text = name + " = ";
                if (first) {
                    first = false;
                } else {
                    text = ", " + text;
                }

                mv.visitVarInsn(ALOAD, tempIndex);
                mv.visitLdcInsn(text);
                mv.visitMethodInsn(
                        INVOKEVIRTUAL,
                        "java/lang/StringBuffer",
                        "append",
                        "(Ljava/lang/Object;)Ljava/lang/StringBuffer;");
                mv.visitInsn(POP);

                mv.visitVarInsn(ALOAD, tempIndex);
                new VariableExpression(name).visit(controller.getAcg());
                operandStack.box();
                mv.visitMethodInsn(INVOKESTATIC, "org/codehaus/groovy/runtime/InvokerHelper", "toString", "(Ljava/lang/Object;)Ljava/lang/String;");
                mv.visitMethodInsn(
                        INVOKEVIRTUAL,
                        "java/lang/StringBuffer",
                        "append",
                        "(Ljava/lang/String;)Ljava/lang/StringBuffer;");
                mv.visitInsn(POP);
                operandStack.remove(1);
            }
            mv.visitVarInsn(ALOAD, tempIndex);
            controller.getCompileStack().removeVar(tempIndex);
        }
    }
    
    public void record(Expression expression) {
        if (assertionTracker==null) return;
        record(assertionTracker.sourceText.getNormalizedColumn(expression.getLineNumber(), expression.getColumnNumber()));
    }

    public void record(Token op) {
        if (assertionTracker==null) return;
        record(assertionTracker.sourceText.getNormalizedColumn(op.getStartLine(), op.getStartColumn()));
    }
    
    private void record(int normalizedColumn) {
        if (assertionTracker==null) return;
        
        MethodVisitor mv = controller.getMethodVisitor();
        OperandStack operandStack = controller.getOperandStack();
        
        operandStack.dup();
        operandStack.box();
        
        mv.visitVarInsn(ALOAD, assertionTracker.recorderIndex);
        operandStack.push(ClassHelper.OBJECT_TYPE);
        //helper.swapWithObject(ClassHelper.OBJECT_TYPE);
        operandStack.swap();
        mv.visitLdcInsn(normalizedColumn);
        mv.visitMethodInsn(
                INVOKEVIRTUAL, 
                "org/codehaus/groovy/runtime/powerassert/ValueRecorder", 
                "record", 
                "(Ljava/lang/Object;I)Ljava/lang/Object;");
        mv.visitInsn(POP);
        operandStack.remove(2);
    }
    
    private void addVariableNames(Expression expression, List<String> list) {
        if (expression instanceof BooleanExpression) {
            BooleanExpression boolExp = (BooleanExpression) expression;
            addVariableNames(boolExp.getExpression(), list);
        } else if (expression instanceof BinaryExpression) {
            BinaryExpression binExp = (BinaryExpression) expression;
            addVariableNames(binExp.getLeftExpression(), list);
            addVariableNames(binExp.getRightExpression(), list);
        } else if (expression instanceof VariableExpression) {
            VariableExpression varExp = (VariableExpression) expression;
            list.add(varExp.getName());
        }
    }

    public void disableTracker() {
        if (assertionTracker==null) return;
        disabledTracker = assertionTracker;
        assertionTracker = null;
    }

    public void reenableTracker() {
        if (disabledTracker==null) return;
        assertionTracker = disabledTracker;
        disabledTracker = null;
    }

}