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Groovy example source code file (AstBuilderFromStringTest.groovy)

This example Groovy source code file (AstBuilderFromStringTest.groovy) 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

argumentlistexpression, blockstatement, blockstatement, constantexpression, constantexpression, expressionstatement, list, methodcallexpression, some, string, variableexpression, variableexpression, variablescope, variablescope

The Groovy AstBuilderFromStringTest.groovy source code

package org.codehaus.groovy.ast.builder

import org.codehaus.groovy.ast.ASTNode
import org.codehaus.groovy.ast.ClassNode
import org.codehaus.groovy.ast.VariableScope
import org.codehaus.groovy.ast.builder.AstBuilder
import org.codehaus.groovy.ast.expr.ConstantExpression
import org.codehaus.groovy.ast.expr.DeclarationExpression
import org.codehaus.groovy.ast.expr.VariableExpression
import org.codehaus.groovy.ast.stmt.BlockStatement
import org.codehaus.groovy.ast.stmt.ExpressionStatement
import org.codehaus.groovy.control.CompilePhase
import org.codehaus.groovy.syntax.Token
import org.codehaus.groovy.syntax.Types
import org.codehaus.groovy.ast.builder.AstBuilder
import org.codehaus.groovy.ast.builder.AstAssert
import org.codehaus.groovy.ast.stmt.ReturnStatement
import org.codehaus.groovy.ast.expr.MethodCallExpression
import org.codehaus.groovy.ast.expr.ArgumentListExpression
import org.codehaus.groovy.ast.stmt.IfStatement
import org.codehaus.groovy.ast.expr.BooleanExpression
import org.codehaus.groovy.ast.expr.BinaryExpression
import org.codehaus.groovy.ast.stmt.BreakStatement
import org.codehaus.groovy.ast.stmt.SwitchStatement
import org.codehaus.groovy.ast.stmt.CaseStatement
import org.codehaus.groovy.ast.stmt.EmptyStatement
import org.objectweb.asm.Opcodes
import org.codehaus.groovy.ast.FieldNode
import org.codehaus.groovy.ast.MethodNode
import org.codehaus.groovy.ast.Parameter
import org.codehaus.groovy.ast.ConstructorNode
import org.codehaus.groovy.ast.ClassHelper

/**
 * Unit test for the AstBuilder class. Shows the usage of how to create AST from string input.  
 * @author Hamlet D'Arcy
 */

public class AstBuilderFromStringTest extends GroovyTestCase {

    private AstBuilder factory

    protected void setUp() {
        super.setUp()
        factory = new AstBuilder()
    }


    /**
     * This shows how to compile a simple script that returns a constant,
     * discarding the generated Script subclass. 
     */
    public void testSimpleConstant() {
        List<ASTNode> result = factory.buildFromString(CompilePhase.CONVERSION, " \"Some String\" ")

        def expected = new BlockStatement(
                [new ExpressionStatement(
                        new ConstantExpression("Some String")
                )],
                new VariableScope()
        )

        AstAssert.assertSyntaxTree([expected], result)
    }

    /**
     * This shows how to compile a script that includes declarations,
     * discarding the generated Script subclass.
     */
    public void testAssignment() {
        List<ASTNode> result = factory.buildFromString(CompilePhase.CONVERSION, " def x = 2; def y = 4 ")

        def expected = new BlockStatement(
                [new ExpressionStatement(
                        new DeclarationExpression(
                                new VariableExpression("x"),
                                Token.newSymbol(Types.EQUAL, 0, 0),
                                new ConstantExpression(2)
                        )
                ),
                        new ExpressionStatement(
                                new DeclarationExpression(
                                        new VariableExpression("y"),
                                        Token.newSymbol(Types.EQUAL, 0, 0),
                                        new ConstantExpression(4)
                                )
                        )],
                new VariableScope()
        )

        AstAssert.assertSyntaxTree([expected], result)
    }

    /**
     * This shows how to compile a script that includes method calls,
     * discarding the generated Script subclass.
     */
    public void testMethodCall() {
        List<ASTNode> result = factory.buildFromString(CompilePhase.CONVERSION, """ println "Hello World" """)

        def expected = new BlockStatement(
                [new ExpressionStatement(
                        new MethodCallExpression(
                                new VariableExpression("this"),
                                new ConstantExpression("println"),
                                new ArgumentListExpression(
                                        [new ConstantExpression("Hello World")]
                                )
                        )
                )],
                new VariableScope()
        )
        AstAssert.assertSyntaxTree([expected], result)
    }

    /**
     * This shows how to get the Script subclass off of the compiled result, compiling
     * all the way to CLASS_GENERATION.
     */
    public void testWithScriptClassAndClassGeneration() {
        List<ASTNode> result = factory.buildFromString(CompilePhase.CLASS_GENERATION, false, " \"Some String\" ")

        def expectedScriptBody = new BlockStatement(
                [new ReturnStatement(
                        new ConstantExpression("Some String")
                )],
                new VariableScope()
        )

        def expectedClassNode = new ClassNode("synthesized", 1024, ClassHelper.make(Script))

        AstAssert.assertSyntaxTree([expectedScriptBody, expectedClassNode], result)
    }

    /**
     * Proves default value is CLASS_GENERATION and statementsOnly = true. 
     */
    public void testDefaultValues() {
        List<ASTNode> result = factory.buildFromString(" \"Some String\" ")

        def expectedScriptBody = new BlockStatement(
                [new ReturnStatement(
                        new ConstantExpression("Some String")
                )],
                new VariableScope()
        )

        AstAssert.assertSyntaxTree([expectedScriptBody], result)
    }

    /**
     * This tests the contract of the build method, trying to pass null
     * arguments when those arguments are required.
     */
    public void testContract() {

        // source is required
        shouldFail(IllegalArgumentException) {
            factory.buildFromString((String) null)
        }

        // source must not be empty
        shouldFail(IllegalArgumentException) {
            factory.buildFromString(" ")
        }
    }


    public void testIfStatement() {

        def result = factory.buildFromString(
                CompilePhase.SEMANTIC_ANALYSIS,
                """ if (foo == bar) println "Hello" else println "World" """)

        def expected = new BlockStatement(
                [new IfStatement(
                        new BooleanExpression(
                                new BinaryExpression(
                                        new VariableExpression("foo"),
                                        new Token(Types.COMPARE_EQUAL, "==", -1, -1),
                                        new VariableExpression("bar")
                                )
                        ),
                        new ExpressionStatement(
                                new MethodCallExpression(
                                        new VariableExpression("this"),
                                        new ConstantExpression("println"),
                                        new ArgumentListExpression(
                                                [new ConstantExpression("Hello")]
                                        )
                                )
                        ),
                        new ExpressionStatement(
                                new MethodCallExpression(
                                        new VariableExpression("this"),
                                        new ConstantExpression("println"),
                                        new ArgumentListExpression(
                                                [new ConstantExpression("World")]
                                        )
                                )
                        )
                )], new VariableScope())
        AstAssert.assertSyntaxTree([expected], result)
    }


    public void testSwitchAndCaseAndBreakStatements() {

        def result = new AstBuilder().buildFromString(CompilePhase.SEMANTIC_ANALYSIS, """
            switch (foo) {
                case 0:
                    break
                case 1:
                case 2:
                    println "<3"
                    break
                default:
                    println ">2"
            }
        """)

        def expected = new BlockStatement(
                [new SwitchStatement(
                        new VariableExpression("foo"),
                        [
                                new CaseStatement(
                                        new ConstantExpression(0),
                                        new BlockStatement(
                                                [new BreakStatement()], new VariableScope())
                                ),
                                new CaseStatement(
                                        new ConstantExpression(1),
                                        new EmptyStatement()
                                ),
                                new CaseStatement(
                                        new ConstantExpression(2),
                                        new BlockStatement(
                                                [
                                                        new ExpressionStatement(
                                                                new MethodCallExpression(
                                                                        new VariableExpression("this"),
                                                                        new ConstantExpression("println"),
                                                                        new ArgumentListExpression(
                                                                                [new ConstantExpression("<3")]
                                                                        )
                                                                )
                                                        ),
                                                        new BreakStatement()
                                                ], new VariableScope()
                                        )
                                )
                        ],
                        new BlockStatement(
                                [new ExpressionStatement(
                                        new MethodCallExpression(
                                                new VariableExpression("this"),
                                                new ConstantExpression("println"),
                                                new ArgumentListExpression(
                                                        [new ConstantExpression(">2")]
                                                )
                                        )
                                )],
                                new VariableScope()
                        )
                )], new VariableScope())

        AstAssert.assertSyntaxTree([expected], result)
    }

    public void testCreatingClassAndMethods() {
        def result = factory.buildFromString(CompilePhase.SEMANTIC_ANALYSIS, """
            class MyClass {
                private String myField = "a field value"
                MyClass() {
                    println "In constructor!"
                }

                def myMethod() {
                    println "In method!"
                }
            }
        """)

        def expected = [
                new BlockStatement(),
                new ClassNode("MyClass", Opcodes.ACC_PUBLIC, ClassHelper.OBJECT_TYPE)
        ]
        AstAssert.assertSyntaxTree(expected, result)

        def classNode = result[1]
        def field = classNode?.fields?.find {FieldNode f -> f.name == 'myField' }
        def expectedField = new FieldNode(
                'myField',
                Opcodes.ACC_PRIVATE,
                ClassHelper.STRING_TYPE,
                classNode,
                new ConstantExpression('a field value')
        )
        AstAssert.assertSyntaxTree([expectedField], [field])

        def method = classNode?.methods?.find {MethodNode m -> m.name == 'myMethod' }
        def expectedMethod = new MethodNode(
                'myMethod',
                Opcodes.ACC_PUBLIC,
                ClassHelper.OBJECT_TYPE,
                [] as Parameter[],
                [] as ClassNode[],
                new BlockStatement(
                        [new ExpressionStatement(
                                new MethodCallExpression(
                                        new VariableExpression('this'),
                                        'println',
                                        new ArgumentListExpression(
                                                new ConstantExpression('In method!')
                                        )
                                ))], new VariableScope())
        )
        AstAssert.assertSyntaxTree([expectedMethod], [method])

        def ctor = classNode?.constructors?.get(0)
        def expectedCtor = new ConstructorNode(
                Opcodes.ACC_PUBLIC,
                [] as Parameter[],
                [] as ClassNode[],
                new BlockStatement(
                        [new ExpressionStatement(
                                new MethodCallExpression(
                                        new VariableExpression('this'),
                                        'println',
                                        new ArgumentListExpression(
                                                new ConstantExpression('In constructor!')
                                        )
                                ))], new VariableScope())
        )
        AstAssert.assertSyntaxTree([expectedCtor], [ctor])
    }
}

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