Writing PyCharm Plugin

the complete plugin project is hosted here

Spent days to get this working, so documenting it here. I reported a PyCharm issue where I want __property__ to be recognized as property. The developer recommend me to write a plugin to fix that. PyCharm plugin must be written in Java (my choice) or Kotlin in IntelliJ. The official document recommend using Gradle. However I can't get it working. Beside what I reported there, I've also bumped into below difficulties:

On my work laptop (MacOS), IDEA struggled to find the right JDK to use. I've to download and install JDK 12. This maybe due to JAVA_HOME settings or some sort. Also Gradle struggled to import and build.
On my personal laptop, IDEA prompt to fix Windows Defender. Gradle also hang at importing.
In plugin.xml, <depends> complained com.intellij.modules.python cannot be resolved.
Installed PyCharm locally and in IDEA set JDK to PyCharm's to solve com.intellij.modules.python, but build fails to find PyKnownDecoratorProvider.

Here's what works for me and all the tricks.

First install PyCharm locally, so its JDK can be used later in IDEA, which has PyKnownDecoratorProvider.

Second, configure project JDKs and libraries to add PyCharm JDK.

In IDEA, create a new project. Select "IntelliJ Platform Plugin" from project templates. NOT the one from "Gradle". I think this is what the official document refers to as "DevKit", which JetBrain does not prefer (but worked for me).

In Project SDK, make sure the PyCharm JDK is selected.

Once project is opened, in plugin.xml, insert:

<depends>com.intellij.modules.python</depends>

This has auto-complete. If IDEA complained ...modules.python can't be found, it means the JDK isn't set up correctly. Once <depends> is specified correctly, add

<extensions defaultExtensionNs="Pythonid">
    <knownDecoratorProvider implementation="pyprop" />
</extensions>

Relevant official doc is here. However, pay attension to change defaultExtensionNs to Pythonid. Otherwise you don't get autocomplete for knownDecoratorProvider and IDEA complains, although later build will pass, PyCharm will load the plugin, it will NOT instantiate your plugin implementation class. When you get autocomplete for knownDecoratorProvider you know you get it right.

knownDecoratorProvider is declared in python-core-common.xml. Note it's qualified name begins with Pythonid that's what we put in defaultExtensionNs.

Now create the class pyprop under src:

import com.jetbrains.python.psi.PyKnownDecoratorProvider;
import org.jetbrains.annotations.Nullable;

public class pyprop implements PyKnownDecoratorProvider {
    @Nullable
    @Override
    public String toKnownDecorator(String decoratorName) {
        return decoratorName.equals("__property__") ? "property" : null;
    }
}

Build and it show succeed.

Debugging

IntelliJ provides good PyCharm plugin debugging. Just hit "debug plugin", it'll bring up a PyCharm instance with the plugin loaded. You can set breakpoints in plugin implementation to make sure they got hit. If so, you know you get it right.

Deploy

Hit "Build" -> "prepare plgin module for deployment". This will package plugin in a "jar" file which can be installed by PyCharm locally.

Finally, the complete plugin is on github

Contents

Debugging

Deploy