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

Lorenzo Bettini

• Publisher: Packt Publishing
• Year: 2016
• ISBN:
  9781786463272
• Edition: 2
• Topic: Computer Science
• Subtopic: Programming
• Index: Computer Science

Learn how to implement a DSL with Xtext and Xtend using easy-to-understand examples and best practicesAbout This Book• Leverage the latest features of Xtext and Xtend to develop a domain-specific language.• Integrate Xtext with popular third party IDEs and get the best out of both worlds.• Discover how to test a DSL implementation and how to customize runtime and IDE aspects of the DSLWho This Book Is ForThis book is targeted at programmers and developers who want to create a domain-specific language with Xtext. They should have a basic familiarity with Eclipse and its functionality. Previous experience with compiler implementation can be helpful but is not necessary since this book will explain all the development stages of a DSL.What You Will Learn• Write Xtext grammar for a DSL;• Use Xtend as an alternative to Java to write cleaner, easier-to-read, and more maintainable code;• Build your Xtext DSLs easily with Maven/Tycho and Gradle;• Write a code generator and an interpreter for a DSL;• Explore the Xtext scoping mechanism for symbol resolution;• Test most aspects of the DSL implementation with JUnit;• Understand best practices in DSL implementations with Xtext and Xtend;• Develop your Xtext DSLs using Continuous Integration mechanisms;• Use an Xtext editor in a web applicationIn DetailXtext 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.Style and approach A step-by step-tutorial with illustrative examples that will let you master using Xtext and implementing DSLs with its custom language, Xtend.

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

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Table of Contents

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

Credits

Foreword

About the Author

Acknowledgments

About the Reviewer

www.PacktPub.com

eBooks, discount offers, and more

Why subscribe?

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

Preface to the second edition

1. Implementing a DSL

Domain-Specific Languages

Need for a new language

Implementing a DSL

Parsing

The Abstract Syntax Tree (AST)

IDE integration

Syntax highlighting

Background validation

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. Working with the Xtend Programming Language

An introduction to Xtend

Using Xtend in your projects

Xtend – a better Java with less "noise"

Types

Methods

Fields and Variables

Operators

Syntactic sugar

Static members and inner types

Literals

Extension methods

The implicit variable – it

Lambda expressions

Multi-line template expressions

Additional operators

Polymorphic method invocation

Enhanced switch expressions

Other Xtend expressions

Xtend IDE

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. Customizing Xtext Components

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

Learning Tests

Testing the outline

Other 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

Custom Content Assist

Typing expressions

Loose type computation, strict type checking

Type computer

Validator

Writing an interpreter

Using the interpreter

Optimizations and fine tuning

Summary

9. Type Checking

SmallJava

Creating the project

SmallJava grammar

Rules for declarations

Rules for statements and syntactic predicates

Rules for expressions

Rule fragments

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 computer 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

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

Eclipse features and p2 repositories

Release engineering

Headless builds

Target platforms

Continuous integration

Introduction to Maven/Tycho

Using the Xtext project wizard

Running the Maven build

Customizing the feature

Using and customizing the target platform

Customizing the pom files

Continuous Integration systems

Maintaining the examples of this book

Your DSL editor on the Web

IntelliJ and Gradle

Pitfalls with Maven/Tycho

Versioning

PDE test problems

Concluding remarks

Installation requirements

Make contributions easy

Summary

12. Xbase

Introduction to Xbase

The common Java type model

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

Validation

Additional Xbase features

Annotations

Reusing Java error markers

Using 'extension'

Using type parameters

Formatter

Further Customizations

Summary

13. Advanced Topics

Creating an Xtext project from an Ecore model

Defining the Ecore model

Creating the Xtext project

Fixing the StandaloneSetup

Tweaking the Ecore model

Derived State

Adding new rules to the language

Switching to an imported Ecore model

Generating EMF classes during the build

Customizing the EMF Java classes

Xcore

Creating the Xcore project

Creating the Xtext project from an existing Xcore model

Modifying the Xcore model

Extending Xbase

Overriding a rule in an Xtext grammar

Customizing the type system

Testing the type computer

Customizing the validator

Customizing the compiler

Using the type system in the compiler

Testing the compiled code

Improving code generation

Smoke tests

Summary

14. ...