Dynamic definitions and types provider for ruby static analysis
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Automated Type Contracts Generation JetBrains incubator project Build Status

ruby-type-inference project is a completely new approach to tackle the problems Ruby dynamic nature and provide more reliable symbol resolution and type inference. It collects some run time data to build type contracts for the methods.

Every time a method is being called, some arguments of particular types are being passed to it. Type Tracker collects all such argument combinations and then builds a special contract which satisfies all encountered argument type tuples.

The approach has its own pros and cons:

  • The obtained contracts utilize real-world usages of code of any complexity so it provides true results even if a method utilizes dynamic Ruby features heavily.
  • The completeness of the contracts obtained for a method highly depends on the coverage of that method, including its callees. That implies the need to merge the data obtained from the different sources (e.g. different projects using the same gem).

This implementation addresses the stated coverage problem by providing the possibility to merge any type contracts at any time.


  • Ruby Type Tracker is a gem with a native extension to attach to ruby processes and trace and intercept all method calls to log type-wise data flow in runtime.

    See arg_scanner documentation for details on usage.

  • Type contract processor server listens for incoming type data (from arg_scanner) and processes it to a compact format.

    The data stored may be used later for better code analysis and also can be shared with other users.

  • Code analysis clients (a RubyMine/IJ+Ruby plugin example) use the contract data to provide features for the users such as code completion, better resolution, etc.

  • (todo) Signature server receives contracts anonymously from the users and provides a compiled contract collections for popular gems.



The arg_scanner gem is used for collecting type information. It can be installed to the target SDK manually and requires MRI Ruby at least 2.3.

Running type tracker

There are two possibilities to use the type tracker: (i) requiring it from Ruby code and (ii) using IJ/RubyMine plugin.

Using in ruby code
  1. In order to collect the data for the script needs a contract server to be up and running; it could be run by running

    ./gradlew contract-creator:runServer

    If you're using RubyMine plugin, there is no need to run server manually since it will be run as a plugin service.

  2. Run the ruby script to be processed via arg-scanner binary.

  3. Use the data collected by the contract server.

Using RubyMine plugin

The easiest way to run the plugin (and the most convenient for its development) is running it with special gradle task against IJ Ultimate snapshot:

./gradlew ide-plugin:runIde

The task will compile the plugin, run IJ Ultimate with plugin "installed" in it. There is no need in running anything manually in that case.

If you want to try it with existing RubyMine instance, you should:

  1. Build it via ./gradlew ide-plugin:buildPlugin
  2. Install plugin in the IDE
    • Navigate to File | Settings | Plugins | Install plugin from disk...
    • Locate plugin in ide-plugin/build/distributions and select.
    • Restart IDE.

Note that due to API changes the plugin may be incompatible with older RM instances.


Any kind of ideas, use cases, contributions and questions are very welcome as the project is just incubating. Please feel free to create issues for any sensible request.