Groovy example source code file (VariableScopeVisitor.java)

This example Groovy source code file (VariableScopeVisitor.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

constantexpression, expression, innerclassnode, parameter, parameter, statestackelement, string, string, tupleexpression, util, variable, variable, variableexpression, variableexpression, variablescope

The Groovy VariableScopeVisitor.java source code

/*
 * Copyright 2003-2011 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;

import org.codehaus.groovy.GroovyBugError;
import org.codehaus.groovy.ast.*;
import org.codehaus.groovy.ast.expr.*;
import org.codehaus.groovy.ast.stmt.BlockStatement;
import org.codehaus.groovy.ast.stmt.CatchStatement;
import org.codehaus.groovy.ast.stmt.ForStatement;
import org.codehaus.groovy.ast.stmt.Statement;
import org.codehaus.groovy.control.SourceUnit;
import org.codehaus.groovy.syntax.Types;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import static java.lang.reflect.Modifier.isFinal;

/**
 * goes through an AST and initializes the scopes
 *
 * @author Jochen Theodorou
 */
public class VariableScopeVisitor extends ClassCodeVisitorSupport {

    private VariableScope currentScope = null;
    private VariableScope headScope = new VariableScope();
    private ClassNode currentClass = null;
    private SourceUnit source;
    private boolean inPropertyExpression = false;
    private boolean isSpecialConstructorCall = false;
    private boolean inConstructor = false;

    private LinkedList stateStack = new LinkedList();

    private class StateStackElement {
        VariableScope scope;
        ClassNode clazz;
        boolean inConstructor;

        StateStackElement() {
            scope = VariableScopeVisitor.this.currentScope;
            clazz = VariableScopeVisitor.this.currentClass;
            inConstructor = VariableScopeVisitor.this.inConstructor;
        }
    }

    public VariableScopeVisitor(SourceUnit source) {
        this.source = source;
        currentScope = headScope;
    }

    // ------------------------------
    // helper methods
    //------------------------------

    private void pushState(boolean isStatic) {
        stateStack.add(new StateStackElement());
        currentScope = new VariableScope(currentScope);
        currentScope.setInStaticContext(isStatic);
    }

    private void pushState() {
        pushState(currentScope.isInStaticContext());
    }

    private void popState() {
        StateStackElement element = (StateStackElement) stateStack.removeLast();
        currentScope = element.scope;
        currentClass = element.clazz;
        inConstructor = element.inConstructor;
    }

    private void declare(Parameter[] parameters, ASTNode node) {
        for (Parameter parameter : parameters) {
            if (parameter.hasInitialExpression()) {
                parameter.getInitialExpression().visit(this);
            }
            declare(parameter, node);
        }
    }

    private void declare(VariableExpression vex) {
        vex.setInStaticContext(currentScope.isInStaticContext());
        declare(vex, vex);
        vex.setAccessedVariable(vex);
    }

    private void declare(Variable var, ASTNode expr) {
        String scopeType = "scope";
        String variableType = "variable";

        if (expr.getClass() == FieldNode.class) {
            scopeType = "class";
            variableType = "field";
        } else if (expr.getClass() == PropertyNode.class) {
            scopeType = "class";
            variableType = "property";
        }

        StringBuilder msg = new StringBuilder();
        msg.append("The current ").append(scopeType);
        msg.append(" already contains a ").append(variableType);
        msg.append(" of the name ").append(var.getName());

        if (currentScope.getDeclaredVariable(var.getName()) != null) {
            addError(msg.toString(), expr);
            return;
        }

        for (VariableScope scope = currentScope.getParent(); scope != null; scope = scope.getParent()) {
            // if we are in a class and no variable is declared until
            // now, then we can break the loop, because we are allowed
            // to declare a variable of the same name as a class member
            if (scope.getClassScope() != null) break;

            if (scope.getDeclaredVariable(var.getName()) != null) {
                // variable already declared
                addError(msg.toString(), expr);
                break;
            }
        }
        // declare the variable even if there was an error to allow more checks
        currentScope.putDeclaredVariable(var);
    }

    protected SourceUnit getSourceUnit() {
        return source;
    }

    private Variable findClassMember(ClassNode cn, String name) {
        if (cn == null) return null;
        if (cn.isScript()) {
            return new DynamicVariable(name, false);
        }

        for (FieldNode fn : cn.getFields()) {
            if (fn.getName().equals(name)) return fn;
        }

        for (MethodNode mn : cn.getMethods()) {
            String pName = getPropertyName(mn);
            if (pName != null && pName.equals(name))
                return new PropertyNode(pName, mn.getModifiers(), getPropertyType(mn), cn, null, null, null);
        }

        for (PropertyNode pn : cn.getProperties()) {
            if (pn.getName().equals(name)) return pn;
        }

        Variable ret = findClassMember(cn.getSuperClass(), name);
        if (ret != null) return ret;
        return findClassMember(cn.getOuterClass(), name);
    }

    private ClassNode getPropertyType(MethodNode m) {
        if (m.getReturnType() != ClassHelper.VOID_TYPE) {
            return m.getReturnType();
        }
        return m.getParameters()[0].getType();
    }

    private String getPropertyName(MethodNode m) {
        String name = m.getName();
        if (!(name.startsWith("set") || name.startsWith("get"))) return null;
        String pname = name.substring(3);
        if (pname.length() == 0) return null;
        pname = java.beans.Introspector.decapitalize(pname);

        if (name.startsWith("get") && (m.getReturnType() == ClassHelper.VOID_TYPE || m.getParameters().length != 0)) {
            return null;
        }
        if (name.startsWith("set") && m.getParameters().length != 1) {
            return null;
        }
        return pname;
    }

    // -------------------------------
    // different Variable based checks
    // -------------------------------

    private Variable checkVariableNameForDeclaration(String name, Expression expression) {
        if ("super".equals(name) || "this".equals(name)) return null;

        VariableScope scope = currentScope;
        Variable var = new DynamicVariable(name, currentScope.isInStaticContext());
        // try to find a declaration of a variable
        while (true) {
            Variable var1;
            var1 = scope.getDeclaredVariable(var.getName());

            if (var1 != null) {
                var = var1;
                break;
            }

            var1 = scope.getReferencedLocalVariable(var.getName());
            if (var1 != null) {
                var = var1;
                break;
            }

            var1 = scope.getReferencedClassVariable(var.getName());
            if (var1 != null) {
                var = var1;
                break;
            }

            ClassNode classScope = scope.getClassScope();
            if (classScope != null) {
                Variable member = findClassMember(classScope, var.getName());
                if (member != null) {
                    boolean staticScope = currentScope.isInStaticContext() || isSpecialConstructorCall;
                    boolean staticMember = member.isInStaticContext();
                    // We don't allow a static context (e.g. a static method) to access
                    // a non-static variable (e.g. a non-static field).
                    if (!(staticScope && !staticMember))
                        var = member;
                }
                break;
            }
            scope = scope.getParent();
        }

        VariableScope end = scope;

        scope = currentScope;
        while (scope != end) {
            if (end.isClassScope() ||
                    (end.isReferencedClassVariable(name) && end.getDeclaredVariable(name) == null)) {
                scope.putReferencedClassVariable(var);
            } else {
                //var.setClosureSharedVariable(var.isClosureSharedVariable() || inClosure);
                scope.putReferencedLocalVariable(var);
            }
            scope = scope.getParent();
        }

        return var;
    }

    /**
     * a property on "this", like this.x is transformed to a
     * direct field access, so we need to check the
     * static context here
     *
     * @param pe the property expression to check
     */
    private void checkPropertyOnExplicitThis(PropertyExpression pe) {
        if (!currentScope.isInStaticContext()) return;
        Expression object = pe.getObjectExpression();
        if (!(object instanceof VariableExpression)) return;
        VariableExpression ve = (VariableExpression) object;
        if (!ve.getName().equals("this")) return;
        String name = pe.getPropertyAsString();
        if (name == null || name.equals("class")) return;
        Variable member = findClassMember(currentClass, name);
        if (member == null) return;
        checkVariableContextAccess(member, pe);
    }

    private void checkVariableContextAccess(Variable v, Expression expr) {
        if (inPropertyExpression || v.isInStaticContext() || !currentScope.isInStaticContext()) return;

        String msg = v.getName() +
                " is declared in a dynamic context, but you tried to" +
                " access it from a static context.";
        addError(msg, expr);

        // declare a static variable to be able to continue the check
        DynamicVariable v2 = new DynamicVariable(v.getName(), currentScope.isInStaticContext());
        currentScope.putDeclaredVariable(v2);
    }

    // ------------------------------
    // code visit
    // ------------------------------

    public void visitBlockStatement(BlockStatement block) {
        pushState();
        block.setVariableScope(currentScope);
        super.visitBlockStatement(block);
        popState();
    }

    public void visitForLoop(ForStatement forLoop) {
        pushState();
        forLoop.setVariableScope(currentScope);
        Parameter p = forLoop.getVariable();
        p.setInStaticContext(currentScope.isInStaticContext());
        if (p != ForStatement.FOR_LOOP_DUMMY) declare(p, forLoop);
        super.visitForLoop(forLoop);
        popState();
    }

    public void visitDeclarationExpression(DeclarationExpression expression) {
        // visit right side first to avoid the usage of a
        // variable before its declaration
        expression.getRightExpression().visit(this);

        if (expression.isMultipleAssignmentDeclaration()) {
            TupleExpression list = expression.getTupleExpression();
            for (Expression e : list.getExpressions()) {
                declare((VariableExpression) e);
            }
        } else {
            declare(expression.getVariableExpression());
        }
    }

    @Override
    public void visitBinaryExpression(BinaryExpression be) {
        super.visitBinaryExpression(be);
        switch (be.getOperation().getType()) {
            case Types.EQUAL: // = assignment
            case Types.BITWISE_AND_EQUAL:
            case Types.BITWISE_OR_EQUAL:
            case Types.BITWISE_XOR_EQUAL:
            case Types.PLUS_EQUAL:
            case Types.MINUS_EQUAL:
            case Types.MULTIPLY_EQUAL:
            case Types.DIVIDE_EQUAL:
            case Types.INTDIV_EQUAL:
            case Types.MOD_EQUAL:
            case Types.POWER_EQUAL:
            case Types.LEFT_SHIFT_EQUAL:
            case Types.RIGHT_SHIFT_EQUAL:
            case Types.RIGHT_SHIFT_UNSIGNED_EQUAL:
                checkFinalFieldAccess(be.getLeftExpression());
                break;
            default:
                break;
        }
    }

    private void checkFinalFieldAccess(Expression expression) {
        // currently not looking for PropertyExpression: dealt with at runtime using ReadOnlyPropertyException
        if (!(expression instanceof VariableExpression) && !(expression instanceof TupleExpression)) return;
        if (expression instanceof TupleExpression) {
            TupleExpression list = (TupleExpression) expression;
            for (Expression e : list.getExpressions()) {
                checkForFinal(expression, (VariableExpression) e);
            }
        } else {
            checkForFinal(expression, (VariableExpression) expression);
        }
    }

    // TODO handle local variables
    private void checkForFinal(final Expression expression, VariableExpression ve) {
        Variable v = ve.getAccessedVariable();
        boolean isFinal = isFinal(v.getModifiers());
        boolean isParameter = v instanceof Parameter;
        if (isFinal && isParameter) {
            addError("Cannot assign a value to final variable '" + v.getName() + "'", expression);
        }
    }

    public void visitVariableExpression(VariableExpression expression) {
        String name = expression.getName();
        Variable v = checkVariableNameForDeclaration(name, expression);
        if (v == null) return;
        expression.setAccessedVariable(v);
        checkVariableContextAccess(v, expression);
    }

    public void visitPropertyExpression(PropertyExpression expression) {
        boolean ipe = inPropertyExpression;
        inPropertyExpression = true;
        expression.getObjectExpression().visit(this);
        inPropertyExpression = false;
        expression.getProperty().visit(this);
        checkPropertyOnExplicitThis(expression);
        inPropertyExpression = ipe;
    }

    public void visitClosureExpression(ClosureExpression expression) {
        pushState();

        expression.setVariableScope(currentScope);

        if (expression.isParameterSpecified()) {
            Parameter[] parameters = expression.getParameters();
            for (Parameter parameter : parameters) {
                parameter.setInStaticContext(currentScope.isInStaticContext());
                if (parameter.hasInitialExpression()) {
                    parameter.getInitialExpression().visit(this);
                }
                declare(parameter, expression);
            }
        } else if (expression.getParameters() != null) {
            Parameter var = new Parameter(ClassHelper.OBJECT_TYPE, "it");
            var.setInStaticContext(currentScope.isInStaticContext());
            currentScope.putDeclaredVariable(var);
        }

        super.visitClosureExpression(expression);
        markClosureSharedVariables();

        popState();
    }

    private void markClosureSharedVariables() {
        VariableScope scope = currentScope;
        for (Iterator<Variable> it = scope.getReferencedLocalVariablesIterator(); it.hasNext(); ) {
            it.next().setClosureSharedVariable(true);
        }
    }

    public void visitCatchStatement(CatchStatement statement) {
        pushState();
        Parameter p = statement.getVariable();
        p.setInStaticContext(currentScope.isInStaticContext());
        declare(p, statement);
        super.visitCatchStatement(statement);
        popState();
    }

    public void visitFieldExpression(FieldExpression expression) {
        String name = expression.getFieldName();
        //TODO: change that to get the correct scope
        Variable v = checkVariableNameForDeclaration(name, expression);
        checkVariableContextAccess(v, expression);
    }

    // ------------------------------
    // class visit
    // ------------------------------

    public void visitClass(ClassNode node) {
        // AIC are already done, doing them here again will lead
        // to wrong scopes
        if (node instanceof InnerClassNode) {
            InnerClassNode in = (InnerClassNode) node;
            if (in.isAnonymous()) return;
        }

        pushState();

        currentClass = node;
        currentScope.setClassScope(node);

        super.visitClass(node);
        popState();
    }

    protected void visitConstructorOrMethod(MethodNode node, boolean isConstructor) {
        pushState(node.isStatic());
        inConstructor = isConstructor;
        node.setVariableScope(currentScope);

        // GROOVY-2156
        Parameter[] parameters = node.getParameters();
        for (Parameter parameter : parameters) {
            visitAnnotations(parameter);
        }

        declare(node.getParameters(), node);

        super.visitConstructorOrMethod(node, isConstructor);
        popState();
    }

    public void visitMethodCallExpression(MethodCallExpression call) {
        if (call.isImplicitThis() && call.getMethod() instanceof ConstantExpression) {
            ConstantExpression methodNameConstant = (ConstantExpression) call.getMethod();
            Object value = methodNameConstant.getText();

            if (!(value instanceof String)) {
                throw new GroovyBugError("tried to make a method call with a non-String constant method name.");
            }

            String methodName = (String) value;
            Variable v = checkVariableNameForDeclaration(methodName, call);
            if (v != null && !(v instanceof DynamicVariable)) {
                checkVariableContextAccess(v, call);
            }

            if (v instanceof VariableExpression || v instanceof Parameter) {
                VariableExpression object = new VariableExpression(v);
                object.setSourcePosition(methodNameConstant);
                call.setObjectExpression(object);
                ConstantExpression method = new ConstantExpression("call");
                method.setSourcePosition(methodNameConstant); // important for GROOVY-4344
                call.setMethod(method);
            }

        }
        super.visitMethodCallExpression(call);
    }

    public void visitConstructorCallExpression(ConstructorCallExpression call) {
        isSpecialConstructorCall = call.isSpecialCall();
        super.visitConstructorCallExpression(call);
        isSpecialConstructorCall = false;
        if (!call.isUsingAnonymousInnerClass()) return;

        pushState();
        InnerClassNode innerClass = (InnerClassNode) call.getType();
        innerClass.setVariableScope(currentScope);
        for (MethodNode method : innerClass.getMethods()) {
            Parameter[] parameters = method.getParameters();
            if (parameters.length == 0) parameters = null; // null means no implicit "it"
            ClosureExpression cl = new ClosureExpression(parameters, method.getCode());
            visitClosureExpression(cl);
        }

        for (FieldNode field : innerClass.getFields()) {
            final Expression expression = field.getInitialExpression();
            if (expression != null) {
                expression.visit(this);
            }
        }

        for (Statement statement : innerClass.getObjectInitializerStatements()) {
            statement.visit(this);
        }
        markClosureSharedVariables();
        popState();
    }

    public void visitProperty(PropertyNode node) {
        pushState(node.isStatic());
        super.visitProperty(node);
        popState();
    }

    public void visitField(FieldNode node) {
        pushState(node.isStatic());
        super.visitField(node);
        popState();
    }

    public void visitAnnotations(AnnotatedNode node) {
        List<AnnotationNode> annotations = node.getAnnotations();
        if (annotations.isEmpty()) return;
        for (AnnotationNode an : annotations) {
            // skip built-in properties
            if (an.isBuiltIn()) continue;
            for (Map.Entry<String, Expression> member : an.getMembers().entrySet()) {
                Expression annMemberValue = member.getValue();
                annMemberValue.visit(this);
            }
        }
    }
}