Friday, September 24, 2010

Migrating from Xtext 0.7.x to Xtext 1.0 in Eclipse Galileo (3.5)

Are you stuck with Eclipse Galileo in your project but still like to use the new features of Xtext 1.0? Xtext 1.0 works fine not only in the newest Eclipse Helios (3.6), but also in Eclipse Galileo (3.5). Galileo users can also benefit from Xtext 1.0 features. The eclipse plugins can be updated by using the Eclipse update mechanism and adding the Xtext update site to the update manager.

After the update of the Xtext plugins, developers may refer to the Xtext documentation (Chapter 11. Migrating from Xtext 0.7.x to 1.0) for a manual on what has to be changed. If projects are heavily customized, the cleanest way to migrate, which is starting a new Xtext project and moving the artifacts from the old to the new projects, might not be desired and developers may prefer following the Migrating Step by Step guidelines. Before follwing these guidelines, I recommend to quickly create a sample project (New|Project...|Xtext Project) with the default settings and running the workflow (GenerateMyDsl.mwe2). This can be a handy reference, e.g. on the new folder structure for the recommended "Rename Package" refactoring. I also recommend to read section 11.2.5. Noteworthy API Changes before fixing compilation errors.

Grammars are backwards compatible. With Xtext 1.0, working on the grammar as a developer has become more convenient. Among other improvements, the content assist was enhanced and more hints for developers were added to prevent grammars with potentially unintended side-effects, e.g. if a rule contains only optional elements and may be consumed from the parser without object instantiation, the developer is given a hint to add an action that creates an object (see Actions in the Xtext documentation).

I was doing this migration for a heavily customized Xtext modeling project, and it turned out it took less effort than expected. The customer is happy with the new features of Xtext 1.0 and the complex project now loads in a bit more than half of the time it took before.