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Gradle Build Tool Docs

The docs project produces the user manual, DSL reference, javadoc and release notes (as well as some other minor bits).

The following is some help for working with the docs, all file paths are relative to this directory unless specified otherwise.

Release Notes#

The release notes are generated from src/docs/release/


Every h2 tag and h3 will be listed in the generated TOC.

After every h3 all content after the first element (usually a p) will be collapsed/expandable, up until the next h3, or h2.

After every h4 all content will be collapsed/expandable, up until the next h4, h3 or h2.

An h3 may include an incubating marker (i) at the end of its text to indicate that the feature is incubating.

Here's an example:

## h2 New and Noteworthy

### h3 Some feature (i)

This is some incubating feature.

#### h4 Some detail

This detail about the feature is collapsed. The reader can expand it if they are interested.


Run the :docs:releaseNotes task to generate the release notes.

User Manual#

The source for the user manual lives @ src/docs/userguide, and is authored in Asciidoctor.

To generate the user manual for the final preview and see all changes, you normally want to run:

./gradlew stageDocs

That will generate all the docs in the build/docs directory.

For development and fast feedback you should use:

./gradlew stageDocs -PquickDocs

Alternatively, if you want to serve the docs in a built-in webserver (http://localhost:8000), you can use:

./gradlew serveDocs -PquickDocs

The flag -PquickDocs disables some slow documentation tasks, like creating the DSL reference or the single page user manual PDF or HTML. This will automatically enter continuous build and rebuild the documentation when you make changes. It takes 30-40 seconds to rebuild the documentation in "quick mode".

If you really want to generate just the user manual, you can run:

./gradlew :docs:userguide

But note that the generated documentation might not be fully functional (e.g. links will not work). This will generate:

  • A multi-page HTML manual in build/working/usermanual/render-multi/ for each chapter. There is a 1-1 mapping from .adoc file to .html file.
  • A single-page HTML manual at build/working/usermanual/render-single-html/userguide_single.html
  • A PDF at build/working/usermanual/render-single-pdf/userguide_single.pdf

Note that PNG files in the source are generated from ".graphml" files in the same directory. You can edit these files with tools like yEd and then generate the associated PNG.

Authoring with AsciiDoc#

To write a chapter in Asciidoctor format, simply place it in src/docs/userguide called <chapter>.adoc.

You will find these references useful when authoring AsciiDoc:

Adding new chapters#

When adding a new chapter to the manual do the following steps: 1. Create a file called <chapter>.adoc in a suitable subdirectory of src/docs/userguide and write the content there. 2. Add the license text to the top of the file and also add an ID for the chapter title. This is required to be able to link directly to the chapter from other chapters, as opposed to linking to a section inside.\ The ID should preferably match the name of the adoc file. For instance, linking to toolchains.adoc is possible with <<toolchains.adoc#toolchains,Text>>, and the declaration looks like:

= Toolchains for JVM projects
3. Include the new chapter file in the userguide_single.adoc. 4. Include the relative link to the new chapter in the header.html

Code Snippets#

Snippets and output belong under src/snippets and are typically included in the user manual. This is a typical example:

Example multi-language sample file listing#

This shows Groovy and Kotlin sample projects under "sample-dir" which is defined as "$projectDir/src/snippets".

└── initScripts/customLogger/
    ├── customLogger.out
    ├── customLogger.sample.conf
    ├── groovy
    │   ├── build.gradle
    │   ├── init.gradle
    │   └── settings.gradle
    └── kotlin
        ├── build.gradle.kts
        ├── customLogger.init.gradle.kts
        └── settings.gradle.kts

Note here that there are 2 sample projects under initScripts/customLogger/: one for the Groovy DSL and one for Kotlin DSL. Also note that there is only 1 customLogger.sample.conf file that tells Exemplar how to execute both groovy and kotlin samples, with 1 customLogger.out file proving the output is identical between the two.

Example Asciidoctor multi-language sample declaration#

.Customizing what Gradle logs

$ gradle -I customLogger.init.gradle.kts build
$ gradle -I init.gradle build

Let's break down this example to explain:

  • Enclosing ==== around the sample includes groups these samples and collapses them
  • include::sample: invokes the SampleIncludeProcessor asciidoctor extension, with a dir relative to src/snippets/, and a list of files separated by ; (only 1 in this example), each with optional tags=... (like Asciidoctor's tags mechanism). We write this once for each DSL dialect. This notes to our front-end code to group these 2 samples and show them with selector tabs.
  • [.multi-language-text.lang-groovy]: Most times the gradle command is identical between Groovy and Kotlin samples, but in this case we need to use [.multi-language-text.lang-*] that our CSS will collapse and switch for the DSL of choice. This is case-sensitive. You can use this construct for any 2 sibling blocks!

It is possible to embed sample sources, commands, and expected output directly in the Asciidoc (or a mixture of embedded and included), but we don't use this for the user manual yet. See the Exemplar documentation if you're interested in this.

Testing docs#

Currently, docs is tested by docs:docsTest, which covers three kinds of code:

  • The code generated by Build Init Plugin, i.e. gradle init task.
  • generate-samples.gradle.kts registers multiple generator tasks that generate the same sample project code as you manually run gradle init.
  • These sample projects will also be published beside the user manual.
  • The code samples under platforms/documentation/docs/src/samples. They are published beside the user manual.
  • The code snippets under platforms/documentation/docs/src/snippets, which are typically included in the user manual.

Note: the terminology sample could refer to different things depending on the context:

  • The code samples under platforms/documentation/docs/src/samples. We'll call them "code samples."
  • The test unit used by exemplar framework. We'll call them "exemplar sample".

The build script of the docs subproject (supprojects/docs/build.gradle) eventually assembles the three kinds of docs code above to exemplar samples and then tests them with exemplar.

org.gradle.samples plugin#

platforms/documentation/docs/build.gradle applies generate-samples.gradle.kts, which further applies an opinionated plugin called org.gradle.samples. The source code of this plugin is here. This plugin adds a Samples extension named samples.

This samples extension is configured in both platforms/documentation/docs/build.gradle and generate-samples.gradle.kts: all docs code to be tested will be assembled into samples.publishedSamples, as follows:

This graph is generated by []( You can copy-paste it to the website to modify it. 

│ documentation/docs/build.gradle    │
│ ┌────────────────────────────────┐ │    ┌─────────────────────────────────┐
│ │ generate-samples.gradle.kts    ├─┼───►│ code generated by init tasks    ├───┐
│ │                                │ │    │                                 │   │
│ └────────────────────────────────┘ │    └─────────────────────────────────┘   │
│                                    │                                          │
│  samples {                         │    ┌─────────────────────────────────┐   │
│    ...                             │    │ code snippets in src/snippets   ├───┤
│    publishedSamples {  ────────────┼─┬─►│                                 │   │
│      ...                           │ │  └─────────────────────────────────┘   │
└────────────────────────────────────┘ │                                        │
                                       │  ┌─────────────────────────────────┐   │
                                       └─►│ code samples in src/samples     ├───┤
                                          │                                 │   │
                                          └─────────────────────────────────┘   │
                                        ┌───────────────────────────────────┐   │
                                        │ org.gradle.samples plugin         │   │
                                        │ ┌─────────────────────────────┐   │   │
┌─────────────┐   Install samples to    │ │ Samples.publishedSamples    │   │   │
│  Exemplar   │   local directory and   │ │                             │   │   │
│             │   test with exemplar    │ │                             │   │   │
│             │◄────────────────────────┤ │                             ◄───┼───┘
│             │                         │ │                             │   │
└─────────────┘                         │ │                             │   │
                                        │ └─────────────────────────────┘   │
                                        │                                   │

The elements in samples.publishedSamples container will later be installed into a local directory (by default docs/build/working/samples/install) as exemplar samples.

After the exemplar examples are installed, docs:docsTest will start testing them (see BaseSamplesTest).

Code samples#

To run the samples tests:

./gradlew :docs:docsTest --tests "*.*"

To run tests for a single sample, let's say from samples/java/application:

./gradlew :docs:docsTest --tests "*"

Note that the samples are also used in samples subproject, see @UsesSample and Sample.

Code snippets#

As an example, you can run Kotlin and Groovy snippets tests from src/snippets/java/toolchain-task/ using:

./gradlew :docs:docsTest --tests "*.snippet-java-toolchain-task_*"

You can also filter the tests for a specific DSL like this:

./gradlew :docs:docsTest --tests "*.snippet-java-toolchain-task_kotlin_*"

Testing with configuration cache#

It is possible to run samples and snippets with the configuration cache enabled to ensure compatibility. You can do that by setting the Gradle property enableConfigurationCacheForDocsTests in the command line or in the file.

./gradlew :docs:docsTest --tests "*.snippet-java-toolchain-task_*" -PenableConfigurationCacheForDocsTests=true

Groovy DSL Reference#

The DSL reference is authored in Docbook syntax, with sources under src/docs/dsl. Much of the content is extracted from code doc comments.

To build it, run:

./gradlew :docs:dslHtml

The output is available under build/working/dsl.

Useful docbook tags#

See the docbook reference for a list of all available tags.

Custom Tags#

This is an inline element which adds a link to the API documentation for a particular class or method.

You can use the <apilink class='org.gradle.api.Project' /> interface to do stuff.

The link will point to the DSL reference for the specified class, if available. Otherwise, it will point to the javadoc for the class.

To link to a method:

<apilink class='org.gradle.api.Project' method="apply(java.util.Map)" />


To build these, run:

./gradlew :docs:javadocAll

The output is available within build/javadoc.

Building all the docs#

There is a convenience task to build all of the documentation:

./gradlew :docs:docs