Book Image

Implementing Domain-Specific Languages with Xtext and Xtend - Second Edition

By : Lorenzo Bettini
4 (1)
Book Image

Implementing Domain-Specific Languages with Xtext and Xtend - Second Edition

4 (1)
By: Lorenzo Bettini

Overview of this book

Xtext is an open source Eclipse framework for implementing domain-specific languages together with IDE functionalities. It lets you implement languages really quickly; most of all, it covers all aspects of a complete language infrastructure, including the parser, code generator, interpreter, and more. This book will enable you to implement Domain Specific Languages (DSL) efficiently, together with their IDE tooling, with Xtext and Xtend. Opening with brief coverage of Xtext features involved in 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. You will then explore the typical programming development workflow with Xtext when we modify the grammar of the DSL. Further, the Xtend programming language (a fully-featured Java-like language tightly integrated with Java) will be introduced. We then explain the main concepts of Xtext, such as validation, code generation, and customizations of runtime and UI aspects. You will have learned how to test a DSL implemented in Xtext with JUnit and will progress to advanced concepts such as type checking and scoping. You will then integrate the typical Continuous Integration systems built in to Xtext DSLs and familiarize yourself with Xbase. By the end of the book, you will manually maintain the EMF model for an Xtext DSL and will see how an Xtext DSL can also be used in IntelliJ.

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Implementing Domain-Specific Languages with Xtext and Xtend - Second Edition
Lorenzo Bettini
Aug, 2016 | 426 pages
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Table of Contents (25 chapters)
Implementing Domain-Specific Languages with Xtext and Xtend - Second Edition
Implementing Domain-Specific Languages with Xtext and Xtend - Second Edition
Credits
Credits
Foreword
Foreword
About the Author
About the Author
Acknowledgments
Acknowledgments
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Preface to the second edition
Preface to the second edition
Free Chapter
1
Implementing a DSL
Implementing a DSL
Domain-Specific Languages
Implementing a DSL
IDE integration
Enter Xtext
The aim of this book
Summary
2
Creating Your First Xtext Language
Creating Your First Xtext Language
A DSL for entities
The Xtext generator
The Eclipse Modeling Framework (EMF)
Improvements to the DSL
Summary
3
Working with the Xtend Programming Language
Working with the Xtend Programming Language
An introduction to Xtend
Xtend – a better Java with less "noise"
Additional operators
Summary
4
Validation
Validation
Validation in Xtext
Quickfixes
Summary
5
Code Generation
Code Generation
Introduction to code generation
Writing a code generator in Xtend
Integration with the Eclipse build mechanism
Standalone command-line compiler
Summary
6
Customizing Xtext Components
Customizing Xtext Components
Dependency injection
Google Guice in Xtext
Customizations of IDE concepts
Custom formatting
Other customizations
Summary
7
Testing
Testing
Introduction to testing
JUnit 4
The ISetup interface
Implementing tests for your DSL
Test suite
Testing the UI
Testing and modularity
Clean code
Summary
8
An Expression Language
An Expression Language
The Expressions DSL
The grammar for the Expressions DSL
Left recursive grammars
Forward references
Typing expressions
Writing an interpreter
Optimizations and fine tuning
Summary
9
Type Checking
Type Checking
SmallJava
First validation rules
Type checking
Improving the UI
Summary
10
Scoping
Scoping
Cross-reference resolution in Xtext
Custom scoping
Global scoping
Providing a library
Classes of the same package
Dealing with super
What to put in the index?
Additional automatic features
Providing a project wizard
Summary
11
Continuous Integration
Continuous Integration
Eclipse features and p2 repositories
Release engineering
Introduction to Maven/Tycho
Using the Xtext project wizard
Continuous Integration systems
Your DSL editor on the Web
IntelliJ and Gradle
Pitfalls with Maven/Tycho
Concluding remarks
Summary
12
Xbase
Xbase
Introduction to Xbase
The Expressions DSL with Xbase
The Entities DSL with Xbase
Additional Xbase features
Summary
13
Advanced Topics
Advanced Topics
Creating an Xtext project from an Ecore model
Switching to an imported Ecore model
Xcore
Extending Xbase
Summary
14
Conclusions
Conclusions
Bibliography
Bibliography
Index
Index

Custom scoping

As soon as a DSL introduces more involved features, such as nested blocks or inheritance relations, the scope provider must be customized according to the semantics of the language.

The Xtext generator generates an Xtend stub class for implementing a custom scope provider. In the SmallJava DSL, it is SmallJavaScopeProvider.

In order to customize the scope provider we redefine the method getScope, and we manually check the reference and the context's class, for example:

override getScope(EObject context, EReference reference) {
  if (reference == SmallJavaPackage.eINSTANCE.SJSymbolRef_Symbol) {
    if (context instanceof ...)
      ...
  } else if (reference ==
        SmallJavaPackage.eINSTANCE.SJMemberSelection_Member) {
      ...
  } else {
    super.getScope(context, reference)
  }
}

Scope for blocks

The default scope provider can be too permissive. For example, in SmallJava, it allows an expression to refer to a variable declaration that is defined after that expression. As...

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