Implementing Domain-Specific Languages with Xtext and Xtend

Lorenzo Bettini

• Publisher: Packt Publishing
• Year: 2013
• ISBN:
  9781782160304
• Edition: 1
• Topic: Computer Science
• Subtopic: Open Source Programming
• Index: Computer Science

In Detail

Xtext is an open source Eclipse framework for implementing domain-specific languages together with its IDE functionalities. It lets you implement languages really quickly, and, most of all, it covers all aspects of a complete language infrastructure, starting from the parser, code generator, interpreter, and more.

"Implementing Domain-Specific Languages with Xtext and Xtend" will teach you how to develop a DSL with Xtext, an Eclipse framework for implementing domain-specific languages. The chapters are like tutorials that describe the main concepts of Xtext such as grammar definition, validation, code generation, customizations, and many more, through uncomplicated and easy-to-understand examples.

Starting with briefly covering the features of Xtext that are involved in a DSL implementation, including integration in an IDE, the book will then introduce you to Xtend as this language will be used in all the examples throughout the book. We then proceed by explaining the main concepts of Xtext, such as validation, code generation, and customizations of runtime and UI aspects. By the end of the book, you will have learned how to test a DSL implemented in Xtext with Junit, in order to follow a test-driven development strategy that will help the developer implement maintainable code that is much faster and cleaner.

A test-driven approach is used throughout the book when presenting advanced concepts such as type checking and scoping. The book also shows you how to build and release a DSL so that it can be installed in Eclipse, and gives you hints on how to build the DSL headlessly in a continuous integration server.

"Implementing Domain-Specific Languages with Xtext and Xtend" aims to complement the official Xtext documentation to explain the main concepts through simplified examples and to teach the best practices for a DSL implementation in Xtext. It is a Beginner's Guide which should set you up for professional development DSL and its Eclipse IDE tooling.

Approach

A step-by-step guide that enables you to quickly implement a DSL with Xtext and Xtend in a test-driven way with the aid of simplified examples.

Who this book is for

This book is for programmers who want to learn about Xtext and how to use it to implement a DSL (or a programming language) together with Eclipse IDE tooling. It assumes that the user is familiar with Eclipse and its functionality. Existing basic knowledge of a compiler implementation would be useful, though not strictly required, since the book will explain all the stages of the development of a DSL.

Implementing Domain-Specific Languages with Xtext and Xtend

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Table of Contents

Implementing Domain-Specific Languages with Xtext and Xtend

Credits

About the Author

Acknowledgement

About the Reviewers

www.PacktPub.com

Support files, eBooks, discount offers, and more

Why Subscribe?

Free Access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Implementing a DSL

Domain Specific Languages

So, why should you create a new language?

Implementing a DSL

Parsing

The Abstract Syntax Tree (AST)

IDE integration

Syntax highlighting

Background parsing

Error markers

Content assist

Hyperlinking

Quickfixes

Outline

Automatic build

Summarizing DSL implementation

Enter Xtext

Installing Xtext

Let's try Xtext

The aim of this book

Summary

2. Creating Your First Xtext Language

A DSL for entities

Creating the project

Xtext projects

Modifying the grammar

Let's try the Editor

The Xtext generator

The Eclipse Modeling Framework (EMF)

Improvements to the DSL

Dealing with types

Summary

3. The Xtend Programming Language

An introduction to Xtend

Using Xtend in your projects

Xtend – a better Java with less "noise"

Extension methods

The implicit variable – it

Lambda expressions

Multi-line template expressions

Additional operators

Polymorphic method invocation

Enhanced switch expressions

Debugging Xtend code

Summary

4. Validation

Validation in Xtext

Default validators

Custom validators

Quickfixes

Textual modification

Model modification

Quickfixes for default validators

Summary

5. Code Generation

Introduction to code generation

Writing a code generator in Xtend

Integration with the Eclipse build mechanism

Standalone command-line compiler

Summary

6. Customizations

Dependency injection

Google Guice in Xtext

Customizations of IDE concepts

Labels

The Outline view

Customizing other aspects

Custom formatting

Other customizations

Summary

7. Testing

Introduction to testing

Junit 4

The ISetup interface

Implementing tests for your DSL

Testing the parser

Testing the validator

Testing the formatter

Testing code generation

Test suite

Testing the UI

Testing the content assist

Testing workbench integration

Testing the editor

Other UI testing frameworks

Testing and modularity

Clean code

Summary

8. An Expression Language

The Expressions DSL

Creating the project

Digression on Xtext grammar rules

The grammar for the Expressions DSL

Left recursive grammars

Associativity

Precedence

The complete grammar

Forward references

Typing expressions

Type provider

Validator

Writing an interpreter

Using the interpreter

Summary

9. Type Checking

SmallJava

Creating the project

SmallJava grammar

Rules for declarations

Rules for statements and syntactic predicates

Rules for expressions

The complete grammar

Utility methods

Testing the grammar

First validation rules

Checking cycles in class hierarchies

Checking member selections

Checking return statements

Checking for duplicates

Type checking

Type provider for SmallJava

Type conformance (subtyping)

Expected types

Checking type conformance

Checking method overriding

Improving the UI

Summary

10. Scoping

Cross-reference resolution in Xtext

Containments and cross-references

The index

Qualified names

Exported objects

The linker and the scope provider

Component interaction

Custom scoping

Scope for blocks

Scope for inheritance and member visibility

Visibility and accessibility

Filtering unwanted objects from the scope

Global scoping

Packages and imports

The index and the containers

Checking duplicates across files

Providing a library

Default imports

Using the library outside Eclipse

Using the library in the type system and scoping

Dealing with super

What to put in the index?

Additional automatic features

Summary

11. Building and Releasing

Release engineering

Headless builds

Target platforms

Continuous integration

Introduction to Buckminster

Installing Buckminster

Using the Xtext Buckminster wizard

Building the p2 repository from Eclipse

Customizations

Defining the target platform

Build headlessly

Maintaining the examples of this book

Summary

12. Xbase

Getting introduced with Xbase

The Expressions DSL with Xbase

Creating the project

The IJvmModelInferrer interface

Code generation

Debugging

The Entities DSL with Xbase

Creating the project

Defining attributes

Defining operations

Imports

Customizations

Summary

13. Bibliography

Index

Implementing Domain-Specific Languages with Xtext and Xtend

Copyright © 2013 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: August 2013

Production Reference: 1140813

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham B3 2PB, UK.

ISBN 978-1-78216-030-4

www.packtpub.com

Cover Image by Suresh Mogre (<[email protected]>)

Credits

Author

Lorenzo Bettini

Reviewers

Dr. Jan Koehnlein

Henrik Lindberg

Pedro J. Molina

Sebastian Zarnekow

Acquisition Editor

James Jones

Lead Technical Editor

Neeshma Ramakrishnan

Technical Editors

Dipika Gaonkar

Anita Nayak

Sonali S. Vernekar

Project Coordinators

Shiksha Chaturvedi

Hardik Patel

Proofreader

Paul Hindle

Indexer

Rekha Nair

Graphics

Sheetal Aute

Ronak Dhruv

Abhinash Sahu

Production Coordinator

Aparna Bhagat

Kirtee Shingan

Cover Work

Aparna Bhagat

About the Author

Lorenzo Bettini is an assistant professor (Researcher) in computer science at Dipartimento di Informatica, Università di Torino, Italy. Previously, he was a Postdoc and a contractual researcher at Dipartimento di Sistemi e Informatica, Università di Firenze, Italy.

He has a Masters Degree in computer science and a PhD in theoretical computer...

Table of contents

• Implementing Domain-Specific Languages with Xtext and Xtend