Chapter 74. Extending the software model

Table of Contents

74.1. Concepts
74.2. Components
74.3. Binaries
74.4. Source sets
74.5. Putting it all together
74.6. About internal views

Support for the software model is currently incubating. Please be aware that the DSL, APIs and other configuration may change in later Gradle versions.

One of the strengths of Gradle has always been its extensibility, and its adaptability to new domains. The software model takes this extensibility to a new level, enabling the deep modeling of specific domains via richly typed DSLs. The following chapter describes how the model and the corresponding DSLs can be extended to support domains like Java, Play Framework or native software development. Before reading this you should be familiar with the Gradle software model rule based configuration and concepts.

The following build script is an example of using a custom software model for building Markdown based documentation:

Example 74.1. an example of using a custom software model

build.gradle

import sample.documentation.DocumentationComponent
import sample.documentation.TextSourceSet
import sample.markdown.MarkdownSourceSet

apply plugin:sample.documentation.DocumentationPlugin
apply plugin:sample.markdown.MarkdownPlugin

model {
    components {
        docs(DocumentationComponent) {
            sources {
                reference(TextSourceSet)
                userguide(MarkdownSourceSet) {
                    generateIndex = true
                    smartQuotes = true
                }
            }
        }
    }
}

Note: The code for this example can be found at samples/customModel/languageType/ in the ‘-all’ distribution of Gradle.


The rest of this chapter is dedicated to explaining what is going on behind this build script.

74.1. Concepts

A custom software model type has a public type, a base interface and internal views. Multiple such types then collaborate to define a custom software model.

74.1.1. Public type and base interfaces

Extended types declare a public type that extends a base interface:

The public type is exposed to build logic.

74.1.2. Internal views

Adding internal views to your model type, you can make some data visible to build logic via a public type, while hiding the rest of the data behind the internal view types. This is covered in a dedicated section below.

74.1.3. Components all the way down

Components are composed of other components. A source set is just a special kind of component representing sources. It might be that the sources are provided, or generated. Similarly, some components are composed of different binaries, which are built by tasks. All buildable components are built by tasks. In the software model, you will write rules to generate both binaries from components and tasks from binaries.

74.2. Components

To declare a custom component type one must extend ComponentSpec, or one of the following, depending on the use case:

  • SourceComponentSpec represents a component which has sources

  • VariantComponentSpec represents a component which generates different binaries based on context (target platforms, build flavors, …​). Such a component generally produces multiple binaries.

  • GeneralComponentSpec is a convenient base interface for components that are built from sources and variant-aware. This is the typical case for a lot of software components, and therefore it should be in most of the cases the base type to be extended.

The core software model includes more types that can be used as base for extension. For example: LibrarySpec and ApplicationSpec can also be extended in this manner. Theses are no-op extensions of GeneralComponentSpec used to describe a software model better by distinguishing libraries and applications components. TestSuiteSpec should be used for all components that describe a test suite.

Example 74.2. Declare a custom component

DocumentationComponent.groovy

@Managed
interface DocumentationComponent extends GeneralComponentSpec {}

Types extending ComponentSpec are registered via a rule annotated with ComponentType:

Example 74.3. Register a custom component

DocumentationPlugin.groovy

class DocumentationPlugin extends RuleSource {
    @ComponentType
    void registerComponent(TypeBuilder<DocumentationComponent> builder) {}
}

74.3. Binaries

To declare a custom binary type one must extend BinarySpec.

Example 74.4. Declare a custom binary

DocumentationBinary.groovy

@Managed
interface DocumentationBinary extends BinarySpec {
    File getOutputDir()
    void setOutputDir(File outputDir)
}

Types extending BinarySpec are registered via a rule annotated with ComponentType:

Example 74.5. Register a custom binary

DocumentationPlugin.groovy

class DocumentationPlugin extends RuleSource {
    @ComponentType
    void registerBinary(TypeBuilder<DocumentationBinary> builder) {}
}

74.4. Source sets

To declare a custom source set type one must extend LanguageSourceSet.

Example 74.6. Declare a custom source set

MarkdownSourceSet.groovy

@Managed
interface MarkdownSourceSet extends LanguageSourceSet {
    boolean isGenerateIndex()
    void setGenerateIndex(boolean generateIndex)

    boolean isSmartQuotes()
    void setSmartQuotes(boolean smartQuotes)
}

Types extending LanguageSourceSet are registered via a rule annotated with ComponentType:

Example 74.7. Register a custom source set

MarkdownPlugin.groovy

class MarkdownPlugin extends RuleSource {
    @ComponentType
    void registerMarkdownLanguage(TypeBuilder<MarkdownSourceSet> builder) {}
}

Setting the language name is mandatory.

74.5. Putting it all together

74.5.1. Generating binaries from components

Binaries generation from components is done via rules annotated with ComponentBinaries. This rule generates a DocumentationBinary named exploded for each DocumentationComponent and sets its outputDir property:

Example 74.8. Generates documentation binaries

DocumentationPlugin.groovy

class DocumentationPlugin extends RuleSource {
    @ComponentBinaries
    void generateDocBinaries(ModelMap<DocumentationBinary> binaries, VariantComponentSpec component, @Path("buildDir") File buildDir) {
        binaries.create("exploded") { binary ->
            outputDir = new File(buildDir, "${component.name}/${binary.name}")
        }
    }
}

74.5.2. Generating tasks from binaries

Tasks generation from binaries is done via rules annotated with BinaryTasks. This rule generates a Copy task for each TextSourceSet of each DocumentationBinary:

Example 74.9. Generates tasks for text source sets

DocumentationPlugin.groovy

class DocumentationPlugin extends RuleSource {
    @BinaryTasks
    void generateTextTasks(ModelMap<Task> tasks, final DocumentationBinary binary) {
        binary.inputs.withType(TextSourceSet) { textSourceSet ->
            def taskName = binary.tasks.taskName("compile", textSourceSet.name)
            def outputDir = new File(binary.outputDir, textSourceSet.name)
            tasks.create(taskName, Copy) {
                from textSourceSet.source
                destinationDir = outputDir
            }
        }
    }
}

This rule generates a MarkdownCompileTask task for each MarkdownSourceSet of each DocumentationBinary:

Example 74.10. Register a custom source set

MarkdownPlugin.groovy

class MarkdownPlugin extends RuleSource {
    @BinaryTasks
    void processMarkdownDocumentation(ModelMap<Task> tasks, final DocumentationBinary binary) {
        binary.inputs.withType(MarkdownSourceSet) { markdownSourceSet ->
            def taskName = binary.tasks.taskName("compile", markdownSourceSet.name)
            def outputDir = new File(binary.outputDir, markdownSourceSet.name)
            tasks.create(taskName, MarkdownHtmlCompile) { compileTask ->
                compileTask.source = markdownSourceSet.source
                compileTask.destinationDir = outputDir
                compileTask.smartQuotes = markdownSourceSet.smartQuotes
                compileTask.generateIndex = markdownSourceSet.generateIndex
            }
        }
    }
}

See the sample source for more on the MarkdownCompileTask task.

74.5.3. Using your custom model

This build script demonstrate usage of the custom model defined in the sections above:

Example 74.11. an example of using a custom software model

build.gradle

import sample.documentation.DocumentationComponent
import sample.documentation.TextSourceSet
import sample.markdown.MarkdownSourceSet

apply plugin:sample.documentation.DocumentationPlugin
apply plugin:sample.markdown.MarkdownPlugin

model {
    components {
        docs(DocumentationComponent) {
            sources {
                reference(TextSourceSet)
                userguide(MarkdownSourceSet) {
                    generateIndex = true
                    smartQuotes = true
                }
            }
        }
    }
}

Note: The code for this example can be found at samples/customModel/languageType/ in the ‘-all’ distribution of Gradle.


And in the components reports for such a build script we can see our model types properly registered:

Example 74.12. components report

Output of gradle -q components

> gradle -q components

------------------------------------------------------------
Root project
------------------------------------------------------------

DocumentationComponent 'docs'
-----------------------------

Source sets
    Markdown source 'docs:userguide'
        srcDir: src/docs/userguide
    Text source 'docs:reference'
        srcDir: src/docs/reference

Binaries
    DocumentationBinary 'docs:exploded'
        build using task: :docsExploded

Note: currently not all plugins register their components, so some components may not be visible here.

74.6. About internal views

Internal views can be added to an already registered type or to a new custom type. In other words, using internal views, you can attach extra properties to already registered components, binaries and source sets types like JvmLibrarySpec, JarBinarySpec or JavaSourceSet and to the custom types you write.

Let’s start with a simple component public type and its internal view declarations:

Example 74.13. public type and internal view declaration

build.gradle

@Managed interface MyComponent extends ComponentSpec {
    String getPublicData()
    void setPublicData(String data)
}
@Managed interface MyComponentInternal extends MyComponent {
    String getInternalData()
    void setInternalData(String internal)
}

The type registration is as follows:

Example 74.14. type registration

build.gradle

class MyPlugin extends RuleSource {
    @ComponentType
    void registerMyComponent(TypeBuilder<MyComponent> builder) {
        builder.internalView(MyComponentInternal)
    }
}

The internalView(type) method of the type builder can be called several times. This is how you would add several internal views to a type.

Now, let’s mutate both public and internal data using some rule:

Example 74.15. public and internal data mutation

build.gradle

class MyPlugin extends RuleSource {
    @Mutate
    void mutateMyComponents(ModelMap<MyComponentInternal> components) {
        components.all { component ->
            component.publicData = "Some PUBLIC data"
            component.internalData = "Some INTERNAL data"
        }
    }
}

Our internalData property should not be exposed to build logic. Let’s check this using the model task on the following build file:

Example 74.16. example build script and model report output

build.gradle

apply plugin: MyPlugin
model {
    components {
        my(MyComponent)
    }
}

Output of gradle -q model

> gradle -q model

------------------------------------------------------------
Root project
------------------------------------------------------------

+ components
      | Type:       org.gradle.platform.base.ComponentSpecContainer
      | Creator:     ComponentBasePlugin.PluginRules#components(ComponentSpecContainer)
      | Rules:
         ⤷ components { ... } @ build.gradle line 42, column 5
         ⤷ MyPlugin#mutateMyComponents(ModelMap<MyComponentInternal>)
    + my
          | Type:       MyComponent
          | Creator:     components { ... } @ build.gradle line 42, column 5 > create(my)
          | Rules:
             ⤷ MyPlugin#mutateMyComponents(ModelMap<MyComponentInternal>) > all()
        + publicData
              | Type:       java.lang.String
              | Value:      Some PUBLIC data
              | Creator:     components { ... } @ build.gradle line 42, column 5 > create(my)
+ tasks
      | Type:       org.gradle.model.ModelMap<org.gradle.api.Task>
      | Creator:     Project.<init>.tasks()
    + assemble
          | Type:       org.gradle.api.DefaultTask
          | Value:      task ':assemble'
          | Creator:     tasks.addPlaceholderAction(assemble)
          | Rules:
             ⤷ copyToTaskContainer
    + build
          | Type:       org.gradle.api.DefaultTask
          | Value:      task ':build'
          | Creator:     tasks.addPlaceholderAction(build)
          | Rules:
             ⤷ copyToTaskContainer
    + buildEnvironment
          | Type:       org.gradle.api.tasks.diagnostics.BuildEnvironmentReportTask
          | Value:      task ':buildEnvironment'
          | Creator:     tasks.addPlaceholderAction(buildEnvironment)
          | Rules:
             ⤷ copyToTaskContainer
    + check
          | Type:       org.gradle.api.DefaultTask
          | Value:      task ':check'
          | Creator:     tasks.addPlaceholderAction(check)
          | Rules:
             ⤷ copyToTaskContainer
    + clean
          | Type:       org.gradle.api.tasks.Delete
          | Value:      task ':clean'
          | Creator:     tasks.addPlaceholderAction(clean)
          | Rules:
             ⤷ copyToTaskContainer
    + components
          | Type:       org.gradle.api.reporting.components.ComponentReport
          | Value:      task ':components'
          | Creator:     tasks.addPlaceholderAction(components)
          | Rules:
             ⤷ copyToTaskContainer
    + dependencies
          | Type:       org.gradle.api.tasks.diagnostics.DependencyReportTask
          | Value:      task ':dependencies'
          | Creator:     tasks.addPlaceholderAction(dependencies)
          | Rules:
             ⤷ copyToTaskContainer
    + dependencyInsight
          | Type:       org.gradle.api.tasks.diagnostics.DependencyInsightReportTask
          | Value:      task ':dependencyInsight'
          | Creator:     tasks.addPlaceholderAction(dependencyInsight)
          | Rules:
             ⤷ HelpTasksPlugin.Rules#addDefaultDependenciesReportConfiguration(DependencyInsightReportTask, ServiceRegistry)
             ⤷ copyToTaskContainer
    + dependentComponents
          | Type:       org.gradle.api.reporting.dependents.DependentComponentsReport
          | Value:      task ':dependentComponents'
          | Creator:     tasks.addPlaceholderAction(dependentComponents)
          | Rules:
             ⤷ copyToTaskContainer
    + help
          | Type:       org.gradle.configuration.Help
          | Value:      task ':help'
          | Creator:     tasks.addPlaceholderAction(help)
          | Rules:
             ⤷ copyToTaskContainer
    + init
          | Type:       org.gradle.buildinit.tasks.InitBuild
          | Value:      task ':init'
          | Creator:     tasks.addPlaceholderAction(init)
          | Rules:
             ⤷ copyToTaskContainer
    + model
          | Type:       org.gradle.api.reporting.model.ModelReport
          | Value:      task ':model'
          | Creator:     tasks.addPlaceholderAction(model)
          | Rules:
             ⤷ copyToTaskContainer
    + projects
          | Type:       org.gradle.api.tasks.diagnostics.ProjectReportTask
          | Value:      task ':projects'
          | Creator:     tasks.addPlaceholderAction(projects)
          | Rules:
             ⤷ copyToTaskContainer
    + properties
          | Type:       org.gradle.api.tasks.diagnostics.PropertyReportTask
          | Value:      task ':properties'
          | Creator:     tasks.addPlaceholderAction(properties)
          | Rules:
             ⤷ copyToTaskContainer
    + tasks
          | Type:       org.gradle.api.tasks.diagnostics.TaskReportTask
          | Value:      task ':tasks'
          | Creator:     tasks.addPlaceholderAction(tasks)
          | Rules:
             ⤷ copyToTaskContainer
    + wrapper
          | Type:       org.gradle.api.tasks.wrapper.Wrapper
          | Value:      task ':wrapper'
          | Creator:     tasks.addPlaceholderAction(wrapper)
          | Rules:
             ⤷ copyToTaskContainer

We can see in this report that publicData is present and that internalData is not.