Gradle Goodness: Using Incremental Task Action

Gradle has incremental build support to speed up our builds. This means Gradle checks input and output for a task and if something changed the task is executed, otherwise the task is skipped. In previous posts we learned how to add incremental build support to our tasks with annotations and inputs and outputs property of a task. When we have a task that has an output file for an input file, like with transformations, we can have a more efficient task using an incremental task action. With an incremental task action we have extra information on the files that are handled by the task. We can have different actions based on if an input file is out of date or removed. This way we can handle only the input files that have changed or removed with incremental builds, instead of all the input files.

To create an incremental task action we must have a task action method (annotated with @TaskAction) that has a single argument of type IncrementalTaskInputs. The IncrementalTaskInputs class has the method outOfDate and removed. These methods take an action, that can be implemented with a closure, with an instance of InputFileDetails as argument. We can get to the input file via this instance and use that for our task logic. When an input file is out of date, because the file contents has changed or the output file has been removed, the action we defined for the outOfDate method is invoked. If the input file is removed the action for the method removed is invoked.

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Gradle Goodness: Change Local Build Cache Directory

Gradle 3.5 introduced the build cache. With the build cache we can reuse task output from builds that can come from different computers. We can also use the build cache feature for our local builds. By default the directory to store the cache is located in the Gradle user home directory on our computer (USER_HOME/.gradle/caches/build-cache-1). We can change the directory for the local cache via settings.gradle of our Gradle project. For example we could configure a directory in our project file structure to be the build cache directory. Then it is easy to clean the cache, because it is a directory not shared by other Gradle projects. With the default directory location in the Gradle user home directory the caches of all Gradle projects we run on our computer are stored in a single directory. And the cache doesn’t shrink and will only grow we might want to have more control of where the cache of a single Gradle project is stored. This way we can easily clean the cache, because all files of a project are stored in the directory for that project.

In the following example settings.gradle file we configure our build cache directory to be the directory build-cache in the root directory of our project where we store our settings.gradle file:

Written with Gradle 3.5.

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Gradle Goodness: Enable Build Cache For All Builds

Gradle 3.5 introduced the build cache. With the build cache we can share task output between builds on different computers. For example the build output from a continuous integration server can be used on a developer’s computer. To use the build cache feature we use the command-line option --build-cache. Instead of using the command-line option --build-cache we can set the Gradle property org.gradle.caching with the value true in the file gradle.properties of our project. To set this property for all our projects we set the property in the gradle.properties file in the Gradle home directory, which is usually at USER_HOME/.gradle/gradle.properties.

In the following example we set the property org.gradle.caching in ~/.gradle/gradle.properties:

If we want to disable the build cache feature set via the global property we can use the command-line option --no-build-cache to disable the build cache for a particular build.

Written with Gradle 3.5.

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Gradle Goodness: Create Shortcut Key To Refresh Gradle Projects In IntellIJ IDEA

We can open a Gradle project in IntelliJ IDEA and get support for Gradle inside IntelliJ. Sometimes we need to refresh the project in IntelliJ IDEA, for example when we add a new dependency or plugin in our Gradle build file. We need to refresh the Gradle project so IntelliJ IDEA can work with the changes. The Gradle tool window has an icon to Refresh all Gradle projects. But this means a mouse action and we want to have a shortcut key so we can leave our hands on the keyboard.

The action Refresh all Gradle projects is actually the action Refresh all external projects. We can add keyboard shortcut key via Preferences | Keymap. We use the search box to search for Refresh all external projects.

We can right click on the found action and select Add Keyboard Shortcut to define a new shortcut key:

Now we simply use the shortcut to refresh our Gradle project when we have made a change in the Gradle build file that IntelliJ IDEA should know about.

Besides have the action in the Gradle tool window we can also add it to the main toolbar. We right click on the main toolbar and select the option Customize Menus and Toolbars…. We can add the action Refresh all external projects here to the toolbar:

Written with Gradle 3.4.1 and IntelliJ IDEA 2016.3.4.

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Gradle Goodness: Skip Task When Input Empty Using @SkipWhenEmpty Annotation

Gradle has excellent incremental build support. This means that Gradle can determine if a task needs to be executed based on the input and output of that task. If for example nothing changed in one of the input and output files, then the task can be skipped. We can add incremental build support for our custom tasks by defining the input and output of the task. We can also define that a task can be skipped when a collection of files or a directory that is the input of the task are empty or not exists. Gradle offers the @SkipWhenEmpty annotation we can apply on the input of our task.

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Gradle Goodness: Check Operating System In Build Scripts

Sometimes we want to check which operating system is used in our build script. For example we have tasks that need to run if the operating system is Windows and not for other operating systems. Gradle has an internal class org.gradle.nativeplatform.platform.internal.DefaultOperatingSystem, but we should not use this class in our build scripts. The class is used internally by Gradle and can change without warning. If we would depend on this class and it changes we break our build scripts. But we can use a class from Ant that is already in Gradle’s class path: org.apache.tools.ant.taskdefs.condition.Os. The class has several methods and constants to check the operating system name, version and architecture. The values are based on the Java system properties os.name, os.version and os.arch.

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Gradle Goodness: Run Task Ignoring Up-to-date Checks

Gradle builds are fast because Gradle supports incremental tasks. This means Gradle can determine if input or output of task has changed, before running the task. If nothing has changed a task is marked a up-to-date and the task is not executed, otherwise the task is executed. If we want execute a task even if it is up-to-date we must use the command line option --rerun-tasks.

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Gradle Goodness: Getting Project Information Into Rule Based Model Configuration

Rule based model configuration in Gradle allows us to have a graph of objects with dependencies that are resolved by Gradle. To make this work Gradle needs to know about the object in this model space. The model space is populated with objects of our own and with objects from Gradle. At time of writing this blog post we can not interact with the Gradle Project object in our rule based model configuration. It is not officially part of the model space. Probably in the future this might change and will the Project object managed by Gradle be part of the model space. Which means we can use then a Project object as input parameter for any rule methods we have. For now the official way to pass project information to the rule based model space is via the model configuration block in our build script. The model configuration block can be used to set properties on objects with values from our Project object.

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