Add IntelliJ IDEA plugin with LSP4IJ integration

[pditommaso]

Summary

This PR implements a complete IntelliJ IDEA plugin for Nextflow language support using LSP4IJ integration, addressing issue #14.

Features Implemented

• Complete LSP4IJ Integration: Proper language server factory and connection provider
• File Type Support: Recognition for .nf, .nf.test, nextflow.config, and *.config files
• Automatic Discovery: Language server JAR detection from common installation paths
• Full Language Features: Code completion, diagnostics, hover, go-to-definition, find references, etc.
• Professional Structure: Follows IntelliJ plugin development best practices

Plugin Architecture

intellij-plugin/ contains the complete plugin implementation with proper LSP4IJ integration.

Requirements

• IntelliJ IDEA 2023.3+
• LSP4IJ plugin installed
• Nextflow Language Server JAR

Installation & Testing

1. Install LSP4IJ plugin in IntelliJ IDEA
2. Download and place language-server-all.jar at ~/.local/share/nextflow/language-server/
3. Build plugin: cd intellij-plugin && ./gradlew jar prepareSandbox
4. Install from build/idea-sandbox/plugins/nextflow-intellij-plugin/

Implementation Notes

• Uses LSP4IJ extension points for proper integration
• Manages language server process lifecycle automatically
• Compiles successfully with correct API usage
• Provides seamless integration with IntelliJ language infrastructure

Closes #14

[angelozerr]

I suggest that you implement a server installer https://github.com/redhat-developer/lsp4ij/blob/main/docs/LSPApi.md#language-server-installer to install the server when it is started.

And as your language server can be downloaded from github asset, I suggest that you try to use declarative installer https://github.com/redhat-developer/lsp4ij/blob/main/docs/UserDefinedLanguageServerTemplate.md#github-asset-download

I am using this declarative installer with user defined ls if you need help to load declarative installer please ask me.

[ewels]

Should this be its own repo? The VSCode plugin is for example. Then it can just load the language server and the two are kept separate..

[pditommaso]

Should this be its own repo?

Possibly, still very experimental

I suggest that you implement a server installer

Interesting !