# Chapter 28. The IDEA Plugin

The IDEA plugin generates files that are used by IntelliJ IDEA, thus making it possible to open the project from IDEA (File - Open Project). Both external dependencies (including associated source and javadoc files) and project dependencies are considered.

What exactly the IDEA plugin generates depends on which other plugins are used:

Table 28.1. IDEA plugin behavior

Plugin | Description
None | Generates an IDEA module file. Also generates an IDEA project and workspace file if the project is the root project.
Java | Adds Java configuration to the module and project files.

One focus of the IDEA plugin is to be open to customization. Each task provides a standardized set of hooks for adding and removing content from the generated files.

## 28.1. Usage

To use the IDEA plugin, include this in your build script:

Example 28.1. Using the IDEA plugin

`build.gradle`

    apply plugin: 'idea'

The IDEA plugin adds a number of tasks to your project. The main tasks that you will use are the `idea` and `cleanIdea` tasks.

## 28.2. Tasks

The IDEA plugin adds the tasks shown below to a project.

Table 28.2. IDEA plugin - Tasks

Task name | Depends on | Type | Description
`idea` | `ideaProject`, `ideaModule`, `ideaWorkspace` | `-` | Generates all IDEA configuration files
`cleanIdea` | `cleanIdeaProject`, `cleanIdeaModule`, `cleanIdeaWorkspace` | `Delete` | Removes all IDEA configuration files
`cleanIdeaProject` | `-` | `Delete` | Removes the IDEA project file
`cleanIdeaModule` | `-` | `Delete` | Removes the IDEA module file
`cleanIdeaWorkspace` | `-` | `Delete` | Removes the IDEA workspace file
`ideaProject` | `-` | `IdeaProject` | Generates the `.ipr` file. This task is only added to the root project.
`ideaModule` | `-` | `IdeaModule` | Generates the `.iml` file
`ideaWorkspace` | `-` | `IdeaWorkspace` | Generates the `.iws` file

Table 28.3. IdeaModule task

Property | Type | Default Value | Default Value with Java Plugin | Description
`moduleDir` | `File` | `projectDir` | `projectDir` | The content root directory of the module. Must not be null.
`outputFile` | `File` | ``projectDir`/`<project.name>`.iml` | - | The `.iml` file. Used to look for existing files and as the target for generation. Must not be null.
`inheritOutputDirs` | `Boolean` | null | null | If `null`, the value in the existing or default module file is used (the default file uses `true`). If `true`, the module output directories will be located below the project output directories. If `false`, the directories specified with the `sourceDirs` and `testSourceDirs` properties are used.
`sourceDirs` | `Set<File>` | empty set | The source directories of `sourceSets.main` | The directories containing the production sources. Must not be null.
`testSourceDirs` | `Set<File>` | empty set | The source directories of `sourceSets.test` | The directories containing the test sources. Must not be null.
`excludeDirs` | `Set<File>` | empty set | - | The directories to be excluded by IDEA. Must not be null.
`outputDir` | `File` | `null` | `null` | The IDEA output directory for the production sources. If null, no entry is created.
`testOutputDir` | `File` | `null` | `null` | The IDEA output directory for the test sources. If null, no entry is created.
`javaVersion` | `String` | `null` | - | If null, the value of the existing or default `.ipr` file is used (the default file uses `inherited`). If set to `inherited`, the project SDK is used. Otherwise, the SDK for the corresponding value of java version is used.
`downloadSources` | `boolean` | `true` | - | Whether to download and add source Jars associated with the dependency Jars.
`downloadJavadoc` | `boolean` | `false` | - | Whether to download and add javadoc Jars associated with the dependency Jars.
`scopes` | `Map` | `[:]` | COMPILE(compile), RUNTIME(runtime - compile), TEST(testRuntime - runtime) | The keys of this map are the IDEA scopes. Each key points to another map that has two keys, plus and minus. The values of those keys are sets of Configuration objects. The files of the plus configurations are added minus the files from the minus configurations.
`variables` | `Map<String, File>` | `[:]` | - | The variables to be used for replacing absolute paths in the .iml file. For example, you might add a `GRADLE_USER_HOME` variable to point to the Gradle user home directory.

Table 28.4. IdeaProject task

Property | Type | Default Value | Default Value with Java Plugin | Description
`subprojects` | `Set<Project>` | `rootProject.allprojects` | - | The subprojects that should be mapped to modules in the `.ipr` file. The subprojects will only be mapped if the IDEA plugin has been applied to them.
`outputFile` | `File` | ``projectDir`/`<project.name>`.ipr` | - | The `.ipr` file. Used to look for existing files and as the target for generation. Must not be null.
`javaVersion` | `String` | `1.6` | - | The Java version used for defining the project SDK.
`wildcards` | `Set<String>` | `['!?*.java', '!?*.groovy']` | - | The wildcard resource patterns. Must not be null.

Table 28.5. IdeaWorkspace task

Property | Type | Default Value | Default Value with Java Plugin | Description
`outputFile` | `File` | ``projectDir`/`<project.name>`.iws` | - | The `.iws` file. Used to look for existing files and as the target for generation. Must not be null.

Table 28.6. Task Hooks

Method | Project Task Argument | Module Task Argument | Workspace Task Argument | Description
``beforeConfigured { arg -> }`` | `Project` | `Module` | `Workspace` | Called after the domain objects have been populated with relevant content of the existing XML file (if there is one).
``whenConfigured { arg -> }`` | `Project` | `Module` | `Workspace` | Called after the domain objects have been populated with content from Gradle's build model.
``withXml { arg -> }`` | `XmlProvider` | `XmlProvider` | `XmlProvider` | Called before the XML file is written to disk.

## 28.3. Customizing the generated files

All IDEA tasks provide the same hooks and behavior for customizing the generated content. However, the workspace file can effectively only be manipulated via the `withXml` hook, because its corresponding domain object is essentially empty.

The tasks recognize existing IDEA files, and merge them with the generated content.

### 28.3.1. Merging

Sections of existing IDEA files that are also the target of generated content will be amended or overwritten, depending on the particular section. The remaining sections will be left as-is.

#### 28.3.1.1. Disabling merging with a complete overwrite

To completely overwrite existing IDEA files, execute a clean task together with its corresponding generation task, for example `gradle cleanIdea idea` (in that order). If you want to make this the default behavior, add `idea.dependsOn(cleanIdea)` to your build script. This makes it unnecessary to execute the clean task explicitly.

Complete overwrite works equally well for individual files, for example by executing`gradle cleanIdeaModule ideaModule`.

### 28.3.2. Hooking into the generation lifecycle

The IDEA plugin provides domain classes modeling the sections of the IDEA files that are autogenerated by Gradle. The generation lifecycle is as follows:

1. If there is an existing file, its whole XML content is parsed and stored in memory; otherwise, a default file is used in its place
2. The domain objects are populated with the relevant content of the existing file
3. The `beforeConfigured` hook is executed
4. The domain objects are populated with content from Gradle's build model, which may require merging with content from the existing file
5. The `whenConfigured` hook is executed
6. All sections modeled by the domain objects are removed from the in-memory XML representation
7. The domain objects inject their content into the in-memory XML representation
8. The `withXml` hook is executed
9. The in-memory XML representation is written to disk

#### 28.3.2.1. Partial overwrite of existing content

A complete overwrite causes all existing content to be discarded, thereby losing any changes made directly in the IDE. The `beforeConfigured` hook makes it possible to overwrite just certain parts of the existing content. The following example removes all existing dependencies from the `Module` domain object:

Example 28.2. Partial Overwrite for Module

`build.gradle`

    ideaModule {
        beforeConfigured { module ->
            module.dependencies.clear()
        }
    }

The resulting module file will only contain Gradle-generated dependency entries, but not any other dependency entries that may have been present in the original file. (In the case of dependency entries, this is also the default behavior.) Other sections of the module file will be either left as-is or merged. The same could be done for the module paths in the project file:

Example 28.3. Partial Overwrite for Project

`build.gradle`

    ideaProject {
        beforeConfigured { project ->
            project.modulePaths.clear()
        }
    }

#### 28.3.2.2. Modifying the fully populated domain objects

The `whenConfigured` hook allows to manipulate the fully populated domain objects. Often this is the preferred way to customize IDEA files. Here is how you would export all the dependencies of an IDEA module:

Example 28.4. Export Dependencies

`build.gradle`

    ideaModule {
        whenConfigured { module ->
            module.dependencies*.exported = true
        }
    }

#### 28.3.2.3. Modifying the XML representation

The `withXml`hook allows to manipulate the in-memory XML representation just before the file gets written to disk. Although Groovy's XML support makes up for a lot, this approach is less convenient than manipulating the domain objects. In return, you get total control over the generated file, including sections not modeled by the domain objects.

Example 28.5. Customizing the XML

`build.gradle`

    ideaProject {
        withXml { provider ->
            provider.node.component.find { it.@name == 'VcsDirectoryMappings' }.mapping.@vcs = 'Git'
        }
    }

## 28.4. Further things to consider

The paths of the dependencies in the generated IDEA files are absolute. If you manually define a path variable pointing to the Gradle dependency cache, IDEA will automatically replace the absolute dependency paths with this path variable. If you use such a path variable, you need to tell the ideaModule task the name of this variable, so that it can do a proper merge without creating duplicates.