JetBrains_intellij-platform-plugin-template/README.md

# IntelliJ Platform Plugin Template

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> **TL;DR:** Click the <kbd>Use this template</kbd> button and clone it in IntelliJ IDEA.

<!-- Plugin description -->
**IntelliJ Platform Plugin Template** is a repository that provides a pure boilerplate template to make it easier
to create a new plugin project (check the [Creating a repository from a template][gh:template] article).

The main goal of this template is to speed up the setup phase of plugin development for both new and experienced
developers by preconfiguring the project scaffold and CI, linking to the proper documentation pages, and keeping
everything organized.

[gh:template]: https://help.github.com/en/enterprise/2.20/user/github/creating-cloning-and-archiving-repositories/creating-a-repository-from-a-template
<!-- Plugin description end -->

If you're still not quite sure what this is all about, read our introduction:
[What is the IntelliJ Platform?][docs:intro]

> **TIP**: Click the <kbd>Watch</kbd> button on the top to be notified about releases containing new features and fixes.

In this README, we will highlight the following elements of template-project creation:

- [Gradle configuration](#gradle-configuration)
- [Plugin template structure](#plugin-template-structure)
- [Plugin configuration file](#plugin-configuration-file)
- [Sample code](#sample-code):
    - listeners – project and dynamic plugin lifecycle
    - services – project-related and application-related services
    - actions – basic action with shortcut binding
- [Continuous integration](#continuous-integration) based on GitHub Actions
    - [Changelog maintenance](#changelog-maintenance) with the Gradle Changelog Plugin
    - [Release flow](#release-flow) using GitHub Releases
    - [Publishing the plugin](#publishing-the-plugin) with the Gradle IntelliJ Plugin

## Getting started

Before we dive into plugin development and everything related to it, it's worth mentioning the benefits of using GitHub
Templates. By creating a new project using the current template, you start with no history and no reference
to this repository. This allows you to create a new repository easily without having to copy and paste previous content,
clone repositories, or clear the history manually.

All you have to do is click the <kbd>Use this template</kbd> button.

![Use this template][file:use-this-template.png]

After using the template to create your blank project, the [Template Cleanup][file:template_cleanup.yml] workflow
will be triggered to override or remove any template-specific configurations, such as the plugin name,
current changelog, etc. Once this is complete, the project is ready to be cloned to your local environment and opened
with [IntelliJ IDEA][jb:download-ij].

For the last step, you have to manually review the configuration variables described
in the [gradle.properties][file:gradle.properties] file and *optionally* move sources
from the *com.github.username.repository* package to the one that works best for you. Then you can get to work
implementing your ideas.

## Gradle configuration

The recommended method for plugin development involves using the [Gradle][gradle] setup
with the [gradle-intellij-plugin][gh:gradle-intellij-plugin] installed. The gradle-intellij-plugin makes it possible
to run the IDE with your plugin and to publish your plugin to the Marketplace Repository.

A project built using the IntelliJ Platform Plugin Template includes a Gradle configuration that's already been set up.
Feel free to read through the [Using Gradle][docs:using-gradle] articles to get a better understanding of your build
and to learn how to customize it.

The most significant parts of the current configuration are:
- Configuration written with [Gradle Kotlin DSL][gradle-kotlin-dsl].
- Kotlin support, with the option to write Java code.
- Integration with the [gradle-changelog-plugin][gh:gradle-changelog-plugin], which automatically patches the change
  notes and description based on the `CHANGELOG.md` and `README.md` files.
- Integration with the [gradle-intellij-plugin][gh:gradle-intellij-plugin] for smoother development.
- Code linting with [detekt][detekt].
- [Plugin publishing][docs:publishing] using the token.

The project-specific configuration file [gradle.properties][file:gradle.properties] contains:

| Property name             | Description                                                                                |
| ------------------------- | ------------------------------------------------------------------------------------------ |
| `pluginGroup`             | Package name - after *using* the template, this will be set to `com.github.username.repo`. |
| `pluginName`              | Plugin name displayed in the Marketplace and the Plugins Repository.                       |
| `pluginVersion`           | The current version of the plugin.                                                         |
| `pluginSinceBuild`        | The `since-build` attribute of the <idea-version> tag.                                     |
| `pluginUntilBuild`        | The `until-build` attribute of the <idea-version> tag.                                     |
| `platformType`            | The type of IDE distribution.                                                              |
| `platformVersion`         | The version of the IntelliJ Platform IDE that will be used to build the plugin.            |
| `platformDownloadSources` | IDE sources downloaded while initializing the Gradle build.                                    |

The properties listed define the plugin itself or configure the [gradle-intellij-plugin][gh:gradle-intellij-plugin] –
check its documentation for more details.

## Plugin template structure

A generated IntelliJ Platform Plugin Template repository contains the following content structure:

```
.
├── CHANGELOG.md            Full change history.
├── LICENSE                 License, MIT by default
├── README.md               README
├── build/                  Output build directory
├── build.gradle.kts        Gradle configuration
├── detekt-config.yml       Detekt configuration
├── gradle
│   └── wrapper/            Gradle Wrapper
├── gradle.properties       Gradle configuration properties
├── gradlew                 *nix Gradle Wrapper binary
├── gradlew.bat             Windows Gradle Wrapper binary
└── src                     Plugin sources
    └── main
        ├── kotlin/         Kotlin source files
        ├── java/           Java source files
        └── resources/      Resources - plugin.xml, icons, messages
```

In addition to the configuration files, the most important part is the `src` directory, which contains our
implementation and the manifest for our plugin – [plugin.xml][file:plugin.xml].

## Plugin configuration file
The plugin configuration file is a [plugin.xml][file:plugin.xml] file located in the `src/main/resources/META-INF`
directory. It provides general information about the plugin, its dependencies, extensions, and listeners.

```xml
<idea-plugin>
    <id>org.jetbrains.plugins.template</id>
    <name>Template</name>
    <vendor>JetBrains</vendor>
    <depends>com.intellij.modules.platform</depends>

    <extensions defaultExtensionNs="com.intellij">
        <applicationService serviceImplementation="..."/>
        <projectService serviceImplementation="..."/>
    </extensions>

    <projectListeners>
        <listener class="..." topic="..."/>
    </projectListeners>
</idea-plugin>
```

You can read more about this file in the [IntelliJ Platform SDK DevGuide][docs:plugin.xml].

## Sample code

The prepared template provides as little code as possible because it is impossible for a general scaffold to fulfill
all the specific requirements for all types of plugins (language support, build tools, VCS related tools).
The template contains only the following files:

```
.
├── MyBundle.kt                         Bundle class providing access to the resources messages
├── listeners
│   └── MyProjectManagerListener.kt     Project Manager listener - handles project lifecycle
└── services
    ├── MyApplicationService.kt         Application-level service available for all projects
    └── MyProjectService.kt             Project level service
```

These files are located in `src/main/kotlin`. This location indicates the language being used. So if you decide to use
Java instead, sources should be located in the `src/main/java` directory.

## Continuous integration

Continuous integration depends on [GitHub Actions][gh:actions], which are a set of workflows that make it possible
to automate your testing and release process. Thanks to such automation, you can delegate the testing and verification
phases to the CI and instead focus on development (and writing more tests).

In the `.github/workflows` directory, you can find definitions for the following GitHub Actions workflows:

- [Build](.github/workflows/build.yml)
    - Triggered on `push` and `pull_request` events.
    - Runs the *Gradle Wrapper Validation Action* to verify the wrapper's checksum.
    - Runs the `verifyPlugin` and `test` Gradle tasks.
    - Builds the plugin with the `buildPlugin` Gradle task and provides the artifact for the next jobs in the workflow.
    - Verifies the plugin using the *IntelliJ Plugin Verifier* tool.
    - Prepares a draft release of the GitHub Releases page for manual verification.
- [Release](.github/workflows/release.yml)
    - Triggered on `released` event.
    - Publishes the plugin to the Marketplace using the provided `PUBLISH_TOKEN`.
    - Sets publish channel depending on the plugin version, i.e. `1.0.0-beta` -> `beta` channel.
    - Patches the Changelog and commits.
- [Template Cleanup](.github/workflows/template-cleanup.yml) 
    - Triggered once on `push` event when a new template-based repository has been created.
    - Overrides the scaffold with files from `.github/template-cleanup` directory.
    - Overrides JetBrains-specific sentences or package names with ones specific to the target repository.
    - Removes redundant files.

All of the workflow files have accurate documentation, so it's a good idea to take a look through their sources.

### Changelog maintenance

When releasing an update, it is important to let your users know what the new version offers. The best way to do this
is to provide release notes.

The changelog is a curated list that contains information about any new features, fixes, and deprecations.
When they are provided, these lists are available in a few different places: the [CHANGELOG.md](./CHANGELOG.md) file,
the [Releases page][gh:releases], the *What's new* section of the Marketplace Plugin page,
and inside of the Plugin Manager's item details.

There are many methods for handling the project's changelog. The one, used in the current template project
is the [Keep a Changelog][keep-a-changelog] approach.

### Release flow

The release process depends on the workflows already described above. When your main branch receives a new pull request
or a regular push, the [Build](.github/workflows/build.yml) workflow runs multiple tests on your plugin and prepares
a draft release.

![Release draft][file:draft-release.png]

The draft release is a working copy of a release, which you can review before publishing. It includes a predefined title
and git tag, which is the current version of the plugin, for example, `v0.0.1`. The changelog is provided
automatically using the [gradle-changelog-plugin][gh:gradle-changelog-plugin]. An artifact file is also built with
the plugin attached. Every new Build overrides the previous draft to keep your *Releases* page clean.

When you edit the draft and use the <kbd>Publish release</kbd> button, GitHub will tag your repository with the given
version and add a new entry to the Releases tab. Next, it will notify users that are *watching* the repository, and it
will trigger the final [Release](.github/workflows/release.yml) workflow.

### Publishing the plugin

Releasing a plugin to the Marketplace is a straightforward operation that uses the `publishPlugin` Gradle task
provided by the [gradle-intellij-plugin][gh:gradle-intellij-plugin]. The [Release](.github/workflows/release.yml)
workflow automates this process by running the task when a new release appears in the GitHub Releases section.

> **TIP**: Set a suffix to the plugin version to publish it in the custom repository channel, i.e. `v1.0.0-beta` will
> push your plugin to the `beta` [release channel][docs:release-channel].

The authorization process relies on the `PUBLISH_TOKEN` secret environment variable, which has to be acquired
through the Secrets section of the repository Settings.

![Settings > Secrets][file:settings-secrets.png]

You can find out how to get that token in the [Providing Your Hub Permanent Token to Gradle][docs:token] article.

> **Important:**
> Before using the automated deployment process, it is necessary to manually create a new plugin in the Marketplace
> to specify options like the license, repository URL, etc. Please follow
> the [Publishing a Plugin][docs:publishing] instructions.

## Useful links

- [IntelliJ Platform SDK DevGuide][docs]
- [IntelliJ Platform UI Guidelines][jb:ui-guidelines]
- [Kotlin UI DSL][docs:kotlin-ui-dsl]
- [IntelliJ SDK Code Samples][gh:code-samples]
- [JetBrains Platform Slack][jb:slack]
- [IntelliJ IDEA Open API and Plugin Development Forum][jb:forum]
- [Keep a Changelog][keep-a-changelog]
- [GitHub Actions][gh:actions]

[docs]: https://www.jetbrains.org/intellij/sdk/docs
[docs:intro]: https://www.jetbrains.org/intellij/sdk/docs/intro/intellij_platform.html
[docs:kotlin-ui-dsl]: https://www.jetbrains.org/intellij/sdk/docs/user_interface_components/kotlin_ui_dsl.html
[docs:plugin.xml]: https://www.jetbrains.org/intellij/sdk/docs/basics/plugin_structure/plugin_configuration_file.html
[docs:publishing]: https://www.jetbrains.org/intellij/sdk/docs/basics/getting_started/publishing_plugin.html
[docs:release-channel]: https://www.jetbrains.org/intellij/sdk/docs/tutorials/build_system/deployment.html#specifying-a-release-channel
[docs:token]: https://www.jetbrains.org/intellij/sdk/docs/tutorials/build_system/deployment.html#providing-your-hub-permanent-token-to-gradle
[docs:using-gradle]: https://www.jetbrains.org/intellij/sdk/docs/tutorials/build_system.html

[file:use-this-template.png]: .github/readme/use-this-template.png
[file:draft-release.png]: .github/readme/draft-release.png
[file:gradle.properties]: ./gradle.properties
[file:plugin.xml]: ./src/main/resources/META-INF/plugin.xml
[file:settings-secrets.png]: .github/readme/settings-secrets.png
[file:template_cleanup.yml]: ./.github/workflows/template-cleanup.yml

[gh:actions]: https://help.github.com/en/actions
[gh:code-samples]: https://github.com/JetBrains/intellij-sdk-code-samples
[gh:gradle-changelog-plugin]: https://github.com/JetBrains/gradle-changelog-plugin
[gh:gradle-intellij-plugin]: https://github.com/JetBrains/gradle-intellij-plugin
[gh:releases]: https://github.com/JetBrains/intellij-platform-plugin-template/releases

[jb:confluence-on-gh]: https://confluence.jetbrains.com/display/ALL/JetBrains+on+GitHub
[jb:download-ij]: https://www.jetbrains.com/idea/download
[jb:forum]: https://intellij-support.jetbrains.com/hc/en-us/community/topics/200366979-IntelliJ-IDEA-Open-API-and-Plugin-Development
[jb:slack]: https://plugins.jetbrains.com/slack
[jb:ui-guidelines]: https://jetbrains.github.io/ui

[keep-a-changelog]: https://keepachangelog.com
[detekt]: https://detekt.github.io/detekt
[gradle]: https://gradle.org
[gradle-kotlin-dsl]: https://docs.gradle.org/current/userguide/kotlin_dsl.html