Launching a Clojure nREPL from IntelliJ

README.md

Adding a Clojure nREPL to an IntelliJ plugin

• Add the JARs for Clojure and tools.nrepl. I had to use clojure-1.6.0 and tools.nrepl-0.2.6, but it may be possible to use more recent versions.
• IntellijNrepl.java has the bulk of the necessary logic.
• Add the action defined in IntellijNrepl.java to the plugin.xml file.
• Install the plugin, relaunch IntelliJ, and jack in! You can now script IntelliJ with Clojure. Refer to the open source Community Edition of IntelliJ for clues on whatever you're trying to do.

IntellijNrepl.java

package squij;

import clojure.lang.*;
import com.intellij.openapi.actionSystem.AnAction;
import com.intellij.openapi.actionSystem.AnActionEvent;
import com.intellij.openapi.project.Project;
import com.intellij.openapi.ui.Messages;
import org.apache.log4j.Logger;
import org.jetbrains.annotations.NotNull;

import java.io.StringWriter;

public class LaunchNrepl extends AnAction {
    private static final Logger LOG = Logger.getLogger(LaunchNrepl.class);
    private static int port = (int) Math.round(50000 + Math.random() * 10000);

    @Override
    public void actionPerformed(@NotNull AnActionEvent event) {
        ClassLoader oldLoader = Thread.currentThread().getContextClassLoader();

        boolean pushed = false;
        try {
            ClassLoader loader = LaunchNrepl.class.getClassLoader();
            Thread.currentThread().setContextClassLoader(loader);
            StringWriter writer = new StringWriter();
            Class.forName("clojure.lang.RT");
            Var.pushThreadBindings(RT.map(clojure.lang.Compiler.LOADER, loader, RT.var("clojure.core", "*warn-on-reflection*"), true, RT.ERR, writer));
            pushed = true;

            IFn require = RT.var("clojure.core", "require");
            require.invoke(Symbol.intern("clojure.tools.nrepl.server"));
            IFn startServer = RT.var("clojure.tools.nrepl.server", "start-server");
            startServer.invoke(Keyword.intern("port"), port);
            System.out.println("started nREPL on port " + LaunchNrepl.port);

            String result = writer.toString();
            if (result.length() > 0) {
                LOG.error("Reflection warnings:\n"+result);
            }
        } catch (Exception e) {
            Messages.showMessageDialog(event.getProject(), e.getMessage(), "Error",
                    Messages.getErrorIcon());
            return;
        } finally {
            if (pushed) Var.popThreadBindings();
            Thread.currentThread().setContextClassLoader(oldLoader);
        }

        LaunchNrepl.showPort(event.getProject());
    }

    static void showPort(Project project) {
        Messages.showMessageDialog(project, "nREPL launched on port " + LaunchNrepl.port, "nREPL launched",
            Messages.getInformationIcon());
    }
}

plugin.xml

<idea-plugin>
  <id>squij</id>
  <name>Squij</name>
  <version>1.0</version>

  <description><![CDATA[
    ]]></description>

  <change-notes><![CDATA[
    ]]>
  </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">
  </extensions>

  <actions>
    <action id="nrepl" class="squij.LaunchNrepl" text="Launch nREPL" />
  </actions>

</idea-plugin>