Creating an Intellij plugin

Background

Intellij IDEA is one of the famous IDEs(Integrated development environment) used for Java development. Intellij has a variant of IDE's that they provide like -

1. Pycharm - For Python
2. Webstorm - For web development
3. IDEA - For Java

etc. In this post, I will show how you can write your own plugin for any of these IDEs. To develop a plugin you need Intellij IDEA IDE. You can use this to create a plugin for any other variant of IDE. In fact, the framework for IDE remains the same, so you can create a plugin that can potentially work in all IDEs. 

To start with download IntelliJ IDEA. I am using version 2019.1.3(Community edition).

Idea

In this plugin, we are going to add a simple action functionality that takes in the selected text and searches on Stack overflow site. This action will be visible when you right-click on the editor panel of your IDE. Let's see how to do that,

Creating an IntelliJ plugin

Open your IDEA and create a new project. File-> New -> Project -> Intellij platform plugin

Once done, click on next, enter your project name and submit. This should create a new project for you. One of the important files is Project\resources\META-INF\plugin.xml. This gives information about your plugin. Think of it as the manifest file of Android project (If you have worked on Android apps before). Got me location is C:\Users\anike\IdeaProjects\StackOverflowSearch\resources\META-INF\plugin.xml 

 and my project name is StackOverflowSearch.

NOTE: You can choose Groovy as well to develop your plugin. I have selected default, which uses Java.

In the source folder create a class called StackoverflowSearch. This is going to be our action class. Make this class extend com.intellij.openapi.actionSystem.AnAction. AnAction is an abstract class provide by Intellij SDK framework. Once you extend it, you will have to implement the abstract methods in it

    @Override
    public void actionPerformed(@NotNull AnActionEvent anActionEvent) {
        
    }

Then you can add the following code to complete your simple action -

import com.intellij.ide.BrowserUtil;
import com.intellij.openapi.actionSystem.AnAction;
import com.intellij.openapi.actionSystem.AnActionEvent;
import com.intellij.openapi.actionSystem.CommonDataKeys;
import com.intellij.openapi.editor.CaretModel;
import com.intellij.openapi.editor.Editor;
import com.intellij.psi.PsiFile;
import org.jetbrains.annotations.NotNull;


public class StackoverflowSearch extends AnAction {
    @Override
    public void actionPerformed(@NotNull AnActionEvent anActionEvent) {
        PsiFile file = anActionEvent.getData(CommonDataKeys.PSI_FILE);
        Editor editor = anActionEvent.getRequiredData(CommonDataKeys.EDITOR);
        CaretModel caretModel = editor.getCaretModel();
        String selectedText = caretModel.getCurrentCaret().getSelectedText();
        BrowserUtil.open("https://stackoverflow.com/search?q=" + selectedText);
    }
}

This essentially gets the selected text from your editor and open a browser URL with that query parameter. If you do not understand much with this code, don't worry just go to the official documentation and see what each class means. For eg. PSIFile - it s file representation in Intellij framework world. You can see more details here. 

Once done, you will have to list this action in the plugin.xml file we saw above. In this file, you should see the <actions> tag. Add below content inside it.

    <action
            id="Action.Stackoverflow.Search"
            class="StackoverflowSearch"
            text="Search Text on Stack Overflow"
            description="Search Text on Stack Overflow">
      <add-to-group group-id="EditorPopupMenu" anchor="last"/>
    </action>

Once done you are all set to go. The only important thing to note above is the add-to-group group-id field. EditorPopupMenu means this action will be shown in Editor when you right-click. You could have other possible values to show it in Console or top menubar.

My complete plugin.xml looks like below -

<idea-plugin>
  <id>com.your.company.unique.plugin.id</id>
  <name>Stackoverflow Search Plugin</name>
  <version>1.0</version>
  <vendor email="opensourceforgeeks@gmail.com" url="http://opensourceforgeeks.blogspot.com/">OSFG</vendor>

  <description><![CDATA[
      Simple plugin to open selexted text in Stack overflow site
    ]]></description>

  <change-notes><![CDATA[
      Simple plugin to open selexted text in Stack overflow site
    ]]>
  </change-notes>

  <!-- please see http://www.jetbrains.org/intellij/sdk/docs/basics/getting_started/build_number_ranges.html for description -->
  <idea-version since-build="173.0"/>

  <!-- please see http://www.jetbrains.org/intellij/sdk/docs/basics/getting_started/plugin_compatibility.html
       on how to target different products -->
  <!-- uncomment to enable plugin in all products
  <depends>com.intellij.modules.lang</depends>
  -->

  <extensions defaultExtensionNs="com.intellij">
    <!-- Add your extensions here -->
  </extensions>

  <actions>
    <!-- Add your actions here -->
    <action
            id="Action.Stackoverflow.Search"
            class="StackoverflowSearch"
            text="Search Text on Stack Overflow"
            description="Search Text on Stack Overflow">
      <add-to-group group-id="EditorPopupMenu" anchor="last"/>
    </action>
  </actions>

</idea-plugin>

Now you can simply run your project,

Run configuration should automatically be created when you click on run. It should be similar to the following -

NOTE:  Notice that the JRE is Intellij Idea SDK.

This should start a new IDE instance with your plugin activate. You can verify your plugin in installed by going to settings(Ctrl_Alt+S) -> Plugins -> Installed

Now you can select a text, right-click and see the "Search Text on Stackoverflow" action. Click that and it should open the Stack overflow site with your selected text as a search parameter,

Distributing the plugin

To distribute the plugin, simply right click your plugin project and select - "Prepare plugin module for deployment". This should export a zip file which can be distributed. You should see a message like below when you have selected the above option.

To know how to install plugin from local disk refer - How to install IntelliJ Idea plugin from local disk

You can also put it into a plugin repository for others to use instead of distributing zip file. For more details on the plugin, repo see here. I will be adding more details on how to create an Intellij plugin. So stay tuned.

Related Links

• Intellij Platform SDK
• How to install IntelliJ Idea plugin from local disk(OSFG)