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This document describes some WALA-specific aspects of our Gradle build system, plus a few general Gradle features that may be of particular interest to WALA developers. However, it is not a Gradle tutorial.

Getting Started

External Dependencies: Patience is a Virtue

Gradle downloads many packages and supporting Java libraries as needed. Your first Gradle build may take a long time. On a fast workstation with a university-grade network and no local caches, my initial run of ./gradlew assemble processTestResources took five minutes. On a decent laptop with residential DSL and no local caches, the same initial build took twenty minutes. Fortunately, user- and project-level Gradle caches will make incremental rebuilds much faster. Rerunning ./gradlew assemble processTestResources with a warm cache in an already-built tree takes under three seconds.

Eclipse

One-Time Eclipse Configuration

To work with WALA inside Eclipse, first install Eclipse Buildship 3.1 or later using either the Eclipse Marketplace or the Eclipse update manager. Buildship integrates Eclipse with Gradle, much like how M2Eclipse integrates Eclipse with Maven. Restart Eclipse after installing this feature.

Importing WALA Projects Into Eclipse

Once you are running a Buildship-enabled Eclipse, use the “Existing Gradle Project” import wizard to import WALA into Eclipse. Select and import the topmost level of your WALA source tree. On the “Import Options” page of the import wizard, leave all settings at their defaults: the “Override workspace settings” option should be off, and the grayed-out “Gradle distribution” choice should be set to “Gradle wrapper”. It is also recommended that you clear the "Gradle user home" dialog box in the Gradle Preferences prior to importing (one issue was resolved this way). You do not need to select each of WALA’s sub-projects; import only the top-level WALA source tree, and the rest will follow.

The first time you import the WALA project, Eclipse will synchronize its project model with the Gradle build configuration, including downloading some large supporting libraries. The “Import Gradle Project” wizard may spend tens of minutes showing “Importing root project: Configure project :” with no movement of its progress bar. This is normal. Be patient during the initial project import, especially if you have a slow network connection.

Note: a pristine WALA source tree is not pre-configured as a group of Eclipse projects. Using the standard Eclipse “Existing Projects into Workspace” import wizard will not work correctly. You must use the “Existing Gradle Project” import wizard instead.

.classpath and .project as Generated Files

You will find no .classpath or .project files anywhere in the Gradle fork of WALA’s git repository. Importing using the “Existing Gradle Project” wizard creates these Eclipse project configuration files automatically based on the underlying Gradle configuration.

Therefore, when working with Eclipse + Gradle, you should treat .classpath and .project files as generated artifacts, not as files to edit directly or through the Eclipse project configuration GUI. For example, avoid using the Java Build Path settings dialog to make changes that are stored in a .classpath file: the modified .classpath file is not git-tracked, so your changes will eventually be lost or overwritten.

The right way to change the contents of any of a .classpath or .project file is to change the Gradle configuration such that the generated .classpath and .project files will have the desired contents, likely by using Gradle’s eclipse plugin. A few WALA sub-projects already use this: look for eclipse.project in */build.gradle for examples.

IntelliJ IDEA

Opening WALA in IntelliJ IDEA

Open the top-level WALA directory as a project; it should have a distinctive badge on its folder icon marking it as a directory containing a recognized IntelliJ IDEA project.

The first time you open the WALA project, IntelliJ IDEA will notify you that “IntelliJ IDEA found a Gradle build script”. Select the “Import Gradle Project” option offered by this notification. IntelliJ IDEA will synchronize its project model with the Gradle build configuration, including downloading some large supporting libraries. This can take tens of minutes, but is only necessary in a clean, never-previously-built tree. Be patient during the initial project open, especially if you have a slow network connection.

Benign Warning About Non-Managed Maven Project

Each time you open the WALA project, IntelliJ IDEA may report “Non-managed pom.xml file found” in its event log. This arises because WALA historically has built using both Gradle and Maven, but WALA in IntelliJ IDEA needs only the Gradle configuration. You can safely ignore this notification, permanently disable it using the offered “Disable notification” link, or even disable the IntelliJ IDEA Maven plugin entirely if you have no other need for it.

Project Configuration as Derived Model

IntelliJ IDEA automatically derives its project models from the Gradle build configuration, including all information about both internal and external build dependencies. However, this synchronization only goes in one direction: from Gradle to IntelliJ IDEA, not from IntelliJ IDEA back into Gradle. If you manipulate the project structure using the IntelliJ IDEA’s user interface, your changes will likely be overwritten the next time IntelliJ IDEA scans the Gradle build configuration.

This particularly applies to settings found in the “Modules” and “Libraries” sections of the “Project Structure” dialog. The right way to change module and library settings is to change the Gradle configuration such that the derived IntelliJ IDEA model is what you want it to be.

Gradle Command Line

You do not need to install Gradle separately. WALA includes its own copy of Gradle, available as the gradlew script in the top-level WALA directory. Use this script for all command-line Gradle actions. For example, to compile all of WALA’s main (non-test) code and gather it into jar archives, run ./gradlew assemble.

In general, most Gradle-generated artifacts will appear somewhere under */build. For example the jar archives created by the assemble task can be found as */build/libs/*.jar. Note, however, that Eclipse-generated artifacts will appear in Eclipse-specific places, such as */bin and */target.

Trustworthy Dependencies For Incremental Builds

Gradle has excellent understanding of task and file dependencies. You can trust it to perform incremental rebuilds rather than always rebuilding from scratch. If you are used to cleaning your build tree and rebuilding from scratch after every change, I recommend that you drop clean as a reflexive extra step and trust Gradle to do incremental builds correctly.

Favorite Build Tasks

Some useful Gradle tasks include:

  • assemble: build WALA’s main (non-test) code

  • build: build all WALA code and run all automated tests

  • javadoc: build all Javadoc documentation

  • publishToMavenLocal: install WALA’s jar files under ~/.m2

  • googleJavaFormat: reformat all Java code to match WALA project standards

  • clean: remove all Gradle-generated artifacts

Tasks in Specific Sub-Projects

When you run ./gradlew in the top-level WALA directory, any tasks you list will be built in all sub-projects. For example, ./gradlew assemble builds all non-test WALA jars in all sub-projects. If you want to build tasks only in specific sub-projects, you have two options:

  1. Give the fully qualified name of the sub-project task. For example, to assemble only the Dalvik jar, you could run ./gradlew :com.ibm.wala.dalvik:assemble.

  2. Run Gradle from within some sub-project directory. For example, to assemble only the Dalvik jar, you could cd com.ibm.wala.dalvik and then run ../gradlew assemble. Note the proper relative path to the top-level Gradle script: ../gradle instead of ./gradlew.

Task Name Abbreviation

Any build task can be abbreviated by shortening each camel-case-delimited word in its name. For example, the processTestResources task can probably be abbreviated as procTeRes or even pTR.

Useful Command-Line Flags

Among Gradle’s command-line flags, I have found the following particularly useful:

  • --continue: keep building non-dependent sub-tasks even after an initial failure. Especially useful in conjunction with the build or test tasks to see multiple test failures rather than giving up after the first failure.

  • -t, --continuous: keep Gradle process running and re-execute the given tasks whenever input files change. Similar to Eclipse’s behavior of updating the build whenever you change and save a file.

  • --tests=…: run only the selected tests. Use in conjunction with the build or test tasks for faster turnaround if you are focusing on getting just one or a few failing tests to pass.

  • --scan: upload a detailed report of the build process to a Gradle-hosted server for further exploration and analysis. The only security here is the obscurity of the generated URL for the build report. If you are not concerned about potentially making your build details public, then --scan is a good way to gain insights into why Gradle did what it did, and how long each piece took.

Composite Builds

Gradle’s composite builds allow a Gradle-managed project to recursively include other Gradle-managed projects, with Gradle managing the entire build process in a coherent, integrated manner. Thus, if you use Gradle to build your WALA-based project, you can easily have it use WALA from your own, private WALA tree instead of from ~/.m2 or the public Maven repository.

This is especially useful if you frequently find yourself switching between multiple different personal or experimental WALA builds. By avoiding ~/.m2, each WALA-based project can be its own composite build, with its own WALA subtree, and no project interferes with any other.