(Quick Reference)

23 Contributing to Grails - Reference Documentation

Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith, Lari Hotari

Version: 3.1.9

23 Contributing to Grails

Grails is an open source project with an active community and we rely heavily on that community to help make Grails better. As such, there are various ways in which people can contribute to Grails. One of these is by writing useful plugins and making them publicly available. In this chapter, we'll look at some of the other options.

23.1 Report Issues in Github's issue tracker

Grails uses Github to track issues in the core framework. Similarly for its documentation there is a separate tracker. If you've found a bug or wish to see a particular feature added, these are the places to start. You'll need to create a (free) github account in order to either submit an issue or comment on an existing one in either of these.

When submitting issues, please provide as much information as possible and in the case of bugs, make sure you explain which versions of Groovy, Grails and various plugins you are using. Other environment details - OS version, JDK, Gradle etc. should also be included. Also, an issue is much more likely to be dealt with if you upload a reproducible sample application on a github repository and provide a link in the issue.

Reviewing issues

There are quite a few old issues in github, some of which may no longer be valid. The core team can't track down these alone, so a very simple contribution that you can make is to verify one or two issues occasionally.

Which issues need verification? Going to the issue tracker will display all issues that haven't been resolved.

Once you've verified an issue, simply add a short comment explaining what you found. Be sure to metion your environment details and grails version.

23.2 Build From Source and Run Tests

If you're interested in contributing fixes and features to any part of grails, you will have to learn how to get hold of the project's source, build it and test it with your own applications. Before you start, make sure you have:
  • A JDK (7 or above)
  • A git client

Once you have all the pre-requisite packages installed, the next step is to download the Grails source code, which is hosted at GitHub in several repositories owned by the "grails" GitHub user. This is a simple case of cloning the repository you're interested in. For example, to get the core framework run:

git clone http://github.com/grails/grails-core.git

This will create a "grails-core" directory in your current working directory containing all the project source files. The next step is to get a Grails installation from the source.

Creating a Grails installation

If you look at the project structure, you'll see that it doesn't look much like a standard GRAILS_HOME installation. But, it's very simple to turn it into one. Just run this from the root directory of the project:

./gradlew install

This will fetch all the standard dependencies required by Grails and then build a GRAILS_HOME installation. Note that this target skips the extensive collection of Grails test classes, which can take some time to complete.

Once the above command has finished, simply set the GRAILS_HOME environment variable to the checkout directory and add the "bin" directory to your path. When you next type grails command to run, you'll be using the version you just built.

If you are using SDKMAN then that can also be used to work with this local installation via the following:

sdk install grails dev /path/to/grails-core

Now you will have a dev version in your local which you can use to test your features.

Running the test suite

All you have to do to run the full suite of tests is:

./gradlew test

These will take a while (15-30 mins), so consider running individual tests using the command line. For example, to run the test spec BinaryPluginSpec simply execute the following command:

./gradlew :grails-core:test --tests *.BinaryPluginSpec

Note that you need to specify the sub-project that the test case resides in, because the top-level "test" target won't work....

Developing in IntelliJ IDEA

You need to run the following gradle task:

./gradlew idea

Then open the project file which is generated in IDEA. Simple!

Developing in STS / Eclipse

You need to run the following gradle task:

./gradlew cleanEclipse eclipse

Before importing projects to STS do the following action:

  • Edit grails-scripts/.classpath and remove the line "<classpathentry kind="src" path="../scripts"/>".

Use "Import->General->Existing Projects into Workspace" to import all projects to STS. There will be a few build errors. To fix them do the following:

  • Add the springloaded-core JAR file in $GRAILS_HOME/lib/org.springsource.springloaded/springloaded-core/jars to grails-core's classpath.
  • Remove "src/test/groovy" from grails-plugin-testing's source path GRECLIPSE-1067
  • Add the jsp-api JAR file in $GRAILS_HOME/lib/javax.servlet.jsp/jsp-api/jars to the classpath of grails-web
  • Fix the source path of grails-scripts. Add linked source folder linking to "../scripts". If you get build errors in grails-scripts, do "../gradlew cleanEclipse eclipse" in that directory and edit the .classpath file again (remove the line "<classpathentry kind="src" path="../scripts"/>"). Remove possible empty "scripts" directory under grails-scripts if you are not able to add the linked folder.
  • Do a clean build for the whole workspace.
  • To use Eclipse GIT scm team provider: Select all projects (except "Servers") in the navigation and right click -> Team -> Share project (not "Share projects"). Choose "Git". Then check "Use or create repository in parent folder of project" and click "Finish".
  • Get the recommended code style settings from the mailing list thread (final style not decided yet, currently profile.xml). Import the code style xml file to STS in Window->Preferences->Java->Code Style->Formatter->Import . Grails code uses spaces instead of tabs for indenting.

Debugging Grails or a Grails application

To enable debugging, run:

grails run-app --debug-jvm

By default Grails forks a JVM to run the application in. The -debug-jvm argument causes the debugger to be associated with the forked JVM. In order to instead attach the debugger to the build system which is going to fork the JVM use the -debug option:

grails -debug run-app

23.3 Submit Patches to Grails Core

If you want to submit patches to the project, you simply need to fork the repository on GitHub rather than clone it directly. Then you will commit your changes to your fork and send a pull request for a core team member to review.

Forking and Pull Requests

One of the benefits of GitHub is the way that you can easily contribute to a project by forking the repository and sending pull requests with your changes.

What follows are some guidelines to help ensure that your pull requests are speedily dealt with and provide the information we need. They will also make your life easier!

Make sure your fork is up to date

Making changes to outdated sources is not a good idea. Someone else may have already made the change.

git pull upstream master

Create a local branch for your changes

Your life will be greatly simplified if you create a local branch to make your changes on. For example, as soon as you fork a repository and clone the fork locally, execute

git checkout -b issue_123

This will create a new local branch called "issue_123" based off the "master" branch. Of course, you can name the branch whatever you like, but a good idea would be to reference the GitHub issue number that the change is relevant to. Each Pull Request should have its own branch.

Create Github issues for non-trivial changes

For any non-trivial changes, raise an issue on github if one doesn't already exist. That helps us keep track of what changes go into each new version of Grails.

Include github issue ID in commit messages

This may not seem particularly important, but having a github issue ID in a commit message means that we can find out at a later date why a change was made. Include the ID in any and all commits that relate to that issue. If a commit isn't related to an issue, then there's no need to include an issue ID.

Make sure your fork is up to date again and rebase

Since the core developers must merge your commits into the main repository, it makes life much easier if your fork on GitHub is up to date before you send a pull request.

Let's say you have the main repository set up as a remote called "upstream" and you want to submit a pull request. Also, all your changes are currently on the local "issue_123" branch but not on "master". The first step involves pulling any changes from the main repository that have been added since you last fetched and merged:

git checkout master
git pull upstream master

This should complete without any problems or conflicts. Next, rebase your local branch against the now up-to-date master:

git checkout issue_123
git rebase master

What this does is rearrange the commits such that all of your changes come after the most recent one in master. Think adding some cards to the top of a deck rather than shuffling them into the pack.

Push your branch to GitHub and send Pull Request

Finally, you must push your changes to your fork on GitHub, otherwise the core developers won't be able to pick them up:

git push origin issue_123

You should not merge your branch to your forks master. If the Pull Request is not accepted, your master will then be out of sync with upstream forever.

You're now ready to send the pull request from the GitHub user interface.

Say what your pull request is for

A pull request can contain any number of commits and it may be related to any number of issues. In the pull request message, please specify the IDs of all issues that the request relates to. Also give a brief description of the work you have done, such as: "I refactored the data binder and added support for custom number editors. Fixes #xxxx".

23.4 Submit Patches to Grails Documentation

Building the Guide

To build the documentation, simply type:

./gradlew docs

Be warned: this command can take a while to complete and you should probably increase your Gradle memory settings by giving the GRADLE_OPTS environment variable a value like

export GRADLE_OPTS="-Xmx512m -XX:MaxPermSize=384m"

Fortunately, you can reduce the overall build time with a couple of useful options. The first allows you to specify the location of the Grails source to use:

./gradlew -Dgrails.home=/home/user/projects/grails-core docs

The Grails source is required because the guide links to its API documentation and the build needs to ensure it's generated. If you don't specify a grails.home property, then the build will fetch the Grails source - a download of 10s of megabytes. It must then compile the Grails source which can take a while too.

Additionally you can create a ~/.gradle/gradle.properties file with this variable set:


The other useful option allows you to disable the generation of the API documentation, since you only need to do it once:

./gradlew -Ddisable.groovydocs=true docs

Again, this can save a significant amount of time and memory.

The main English user guide is generated in the build/docs directory, with the guide sub-directory containing the user guide part and the ref folder containing the reference material. To view the user guide, simply open build/docs/index.html.


The publishing system for the user guide is the same as the one for Grails projects. You write your chapters and sections in the gdoc wiki format which is then converted to HTML for the final guide. Each chapter is a top-level gdoc file in the src/<lang>/guide directory. Sections and sub-sections then go into directories with the same name as the chapter gdoc but without the suffix.

The structure of the user guide is defined in the src/<lang>/guide/toc.yml file, which is a YAML file. This file also defines the (language-specific) section titles. If you add or remove a gdoc file, you must update the TOC as well!

The src/<lang>/ref directory contains the source for the reference sidebar. Each directory is the name of a category, which also appears in the docs. Hence the directories need different names for the different languages. Inside the directories go the gdoc files, whose names match the names of the methods, commands, properties or whatever that the files describe.


This project can host multiple translations of the user guide, with src/en being the main one. To add another one, simply create a new language directory under src and copy into it all the files under src/en. The build will take care of the rest.

Once you have a copy of the original guide, you can use the {hidden} macro to wrap the English text that you have replaced, rather than remove it. This makes it easier to compare changes to the English guide against your translation. For example:

When you create a Grails application with the [create-app|commandLine] command,
Grails doesn't automatically create an Ant build.xml file but you can generate
one with the [integrate-with|commandLine] command:

Quando crias uma aplicação Grails com o comando [create-app|commandLine], Grails não cria automaticamente um ficheiro de construção Ant build.xml mas podes gerar um com o comando [integrate-with|commandLine]:

Because the English text remains in your gdoc files, diff will show differences on the English lines. You can then use the output of diff to see which bits of your translation need updating. On top of that, the {hidden} macro ensures that the text inside it is not displayed in the browser, although you can display it by adding this URL as a bookmark: javascript:toggleHidden(); (requires you to build the user guide with Grails 2.0 M2 or later).

Even better, you can use the left_to_do.groovy script in the root of the project to see what still needs translating. You run it like so:

./left_to_do.groovy es

This will then print out a recursive diff of the given translation against the reference English user guide. Anything in {hidden} blocks that hasn't changed since being translated will not appear in the diff output. In other words, all you will see is content that hasn't been translated yet and content that has changed since it was translated. Note that {code} blocks are ignored, so you don't need to include them inside {hidden} macros.

To provide translations for the headers, such as the user guide title and subtitle, just add language specific entries in the 'resources/doc.properties' file like so:

es.title=El Grails Framework

For each language translation, properties beginning <lang>. will override the standard ones. In the above example, the user guide title will be El Grails Framework for the Spanish translation. Also, translators can be credited by adding a '<lang>.translators' property:

fr.translators=Stéphane Maldini

This should be a comma-separated list of names (or the native language equivalent) and it will be displayed as a "Translated by" header in the user guide itself.

You can build specific translations very easily using the publishGuide_* and publishPdf_* tasks. For example, to build both the French HTML and PDF user guides, simply execute

./gradlew publishPdf_fr

Each translation is generated in its own directory, so for example the French guide will end up in build/docs/fr. You can then view the translated guide by opening build/docs/<lang>/index.html.

All translations are created as part of the Hudson CI build for the grails-doc project, so you can easily see what the current state is without having to build the docs yourself.