jEdit Ruby Editor Plugin

Rob McKinnon

http://jedit.org/ruby/

The Web says ...

• "The Ruby Editor Plugin for jEdit is a joy to use. ... a great open source Ruby Editor, good for Rails work too ... I recommend it"

                        - Review of JEdit as a Ruby on Rails IDE | Data Inadequate

• "I eventually settled on Jedit for Ruby as recipient of the 'best free Ruby IDE I found today' award."

                        - Ruby IDE - a quick opinion | exactly one turtle

Why a new editor?

• Started as a twinkle in my eye at RubyConf 2004 ...
• ... and as a few beanshell macros for jEdit
• Wanted to:
•          have auto-insert 'end' - the killer feature
•          prove naive type-based completion was possible
•          have syntax aware navigation
•          ... [insert your idea here]

What's jEdit?

• jEdit - a programmer's text editor
• Free Software released under GPL
• Core written by Slava Pestov (started he was 15)
• Plugins written by the masses (like me)
• Implemented in Java ...

Why a jEdit Ruby Editor Plugin?

• Yeah ... it's Java ... I know ... but:
•          I'd worked on jEdit plugins before
•          Works on GNU/Linux, Mac OSX and Windows
•          Allowed me to use JRuby parser
•          A neat Free Software programmer's editor!

Why not the Eclipse Plugin?

• Find the Eclipse user interface constraining
• Don't like the Ruby Eclipse license, it's CPL
• Faster for me to develop a jEdit plugin

Plugin Features

• Auto-indent and insert 'end'
• File structure popup
• Syntax error highlighting
• Type-based method completion
  
  if it quacks like a duck it'll probably waddle like a duck
• Integrated RDoc viewer

Implementation

• org.jedit.ruby
• • ast
  • cache
  • completion
  • icons
  • parser
  • ri
  • structure
  • test
  • utils

Parsing with JRuby

  DefaultRubyParser parser = new DefaultRubyParser();
  parser.init(new RubyParserConfiguration());

  LexerSource source = LexerSource.getSource(filePath, content);

  RubyParserResult result = parser.parse(source);

  Node node = result.getAST();
        

Walking Abstract Syntax Tree

  Node node = result.getAST();

  RubyNodeVisitor visitor = new RubyNodeVisitor(lineCounter, moduleMembers, classMembers, methodMembers, listeners);

  if (node != null) {
      node.accept(visitor);
  }

  List members = visitor.getMembers();
        

NodeVisitor Implementation

class RubyNodeVisitor extends AbstractVisitor { ...

    protected void visitNode(Node node) { ...

    public void visitBlockNode(BlockNode node) { ...

    public void visitNewlineNode(NewlineNode node) { ...

    public void visitModuleNode(ModuleNode node) { ...

    public void visitClassNode(ClassNode node) { ...

    public void visitDefnNode(DefnNode node) { ...

    public void visitDefsNode(DefsNode node) { ...

    public void visitScopeNode(ScopeNode node) { ...
        

Parsing problems

• JRuby doesn't report node start offsets (only end offsets)
• I use regular expressions to identify start offsets - brittle
• Problems with single line modules, etc
• Auto-indent and insert 'end' also uses regular expressions

Getting RDocs into Java

• Use RI YAML format
• Didn't want to write a Java YAML parser
• Instead use Ruby to create serialized Java object XML files
• Wrote Java classes to represent RDoc
• YAML+Ruby -> serialized Java XML -> deserialized at runtime

Popularity

• Home page: 40 visitors a day, 7800 in total
• Download pg: 27 visitors a day, 5200 in total
• Top of Google search for "Ruby editor"

Download page by country

Download page by continent

Future features

• Import RDoc - gives you method completion for import
• Find usages
• Goto declaration
• Incremental selection
• Extract variable
• Extract method
• Code completion for user classes

Final words

• "I've now been using jEdit fairly intensively for the past few days and have to say I'm a convert. ... it's a highly capable editor and I highly recommend checking it out."

                        - Editors and IDEs | Livsey.org