Pathological

Pathological is a Ruby tool that provides a lightweight mechanism for managing your project's load path.

When you're writing a gem, you don't have to worry about paths much, because Rubygems makes sure that lib/ makes it into your path for you. On the other hand, if you have large Ruby projects which aren't organized as gems, you may encounter some of the following problems:

• If you don't have relative requires, you have to run your project from the project root.

• If you want relative requires, you have something nasty like this in your code:

  require File.expand_path(File.join(File.dirname(__FILE__), 'myfile'))
  

• Ruby 1.9.2 breaks your load path if you are expecting . to be in it. You might have to use require_relative or similar to remedy this.

• You have symlinks to shared libraries or non-gemified vendor code living all over your project in order to keep your load paths sane.

Pathological provides one way to manage these issues.

Getting started with pathological is easy. First, make a file called Pathfile at your project root:

$ cd path/to/myproject
$ touch Pathfile

Now require the gem at the start of any executable ruby file:

#!/usr/bin/env ruby

require "bundler/setup" # If you're using bundler
require "pathological"

# other requires...

Now your project root will be in your load path. If your project has, for example, lib/foo.rb, then require lib/foo will work in any of your ruby files. This works because when Pathological is required it will search up the directory tree until it finds a Pathfile. (It will raise an error if one cannot be found).

Note that Pathological should be the first require in your main file so that it will be loaded first. An exception to this is when you're using Bundler, in which case you should require bundler/setup before Pathological (and of course you should have gem "pathological" in your Gemfile).

Pathfiles should be kept in version control.

To add more paths to your load path, just put the paths in your Pathfile. The paths are relative to the location of the Pathfile. The paths will be inserted in the order they appear; the project root itself will be first. If any of the paths are not valid directories, then an exception will be raised when Pathological is required.

Suppose that you have a directory structure like this:

repos/
|-shared_lib/
| `-common.rb
`-my_project/
  |-Pathfile
  |-run_my_project.rb
  `-foo.rb

and that Pathfile contains the following:

../shared_lib

Then inside run_my_project.rb:

require "pathological"
require "foo"
require "common"
# ...

Pathological is packaged as a Rubygem and hence can be trivially installed with

$ gem install pathological

In some cases, you might want slightly different behavior. This customization is done through the use of custom modes. You may use any combination of modes.

This adds debugging statements to STDOUT that explain what Pathological is doing.

In this mode, the project root (where the Pathfile is located) is not added to the load path (so only paths specified in the Pathfile will be loaded).

This is used if you don't want to raise exceptions if you have bad paths (i.e. non-existent paths or not directories) in your Pathfile.

Bundlerize mode enables Bundler to work with your project regardless of your current directory, in the same way as Pathological, by attempting to set the BUNDLE_GEMFILE environment variable to match the directory where the Pathfile is located. Note that you have to run this before requiring bundler/setup. Also, this will not take effect if you are running with bundle exec.

This mode makes Pathological add the unique parents of all paths it finds (instead of the paths themselves). The purpose of parentdir is to enable Pathological to work in a drop-in fashion with legacy code written with all requires being relative to the root of the codebase. Note that this will allow one to require files located in any child of the parents, not just from the directories specified in the Pathfile. This mode should be avoided if possible.

There are two ways to specify modes. First, you can enable any modes you want using the Pathological API:

require "pathological/base"
Pathological.debug_mode
Pathological.parentdir_mode
Pathological.add_paths!

A quicker way is also provided: if you only need to use one special mode, then there is a dedicated file you can require:

require "pathological/debug"

For even more configurable custom integration with Pathological, a public API is provided. See the generated documentation for details on the following public methods:

• Pathological#add_paths!
• Pathological#find_load_paths
• Pathological#find_pathfile
• Pathological#reset!
• Pathological#copy_outside_paths!

Pathological is intended as a replacement for manually munging the load path in your application when you want to load code from other locations. If you can turn each of your dependencies into a gem and then use bundler to manage the dependencies, do that instead.

Pathological does its best to figure out where the Pathfile it should use is located, based on the call stack. For instance, if you run /foo/bar.rb and that requires Pathological, then it will search for /foo/Pathfile and -- failing that -- /Pathfile. However, if /foo/bar.rb does not require Pathological, but loads a ruby file in /baz/quux.rb, and that file requires Pathological, then Pathological searches for /baz/Pathfile and then /Pathfile.

Any code loading situation which does not preserve a sane load path will be incompatible with Pathological. For instance, if you eval() some code that requires Pathological, Pathological has no way of telling where that code originally lived, and will probably behave in an unexpected way. One place this commonly occurs is with rack webservers (e.g., Rackup, Unicorn) that load a config.ru. This file is instance_evaled and so requiring Pathological from your config.ru will not work as expected. In these cases, require Pathological in your app directly.

Pathological was written by the following Ooyala engineers:

• Daniel MacDougall
• Caleb Spare
• Sami Abu-El-Haija
• Evan Chan

• Harry Robertson for the idea to not use a dot-prefixed configuration file

• Hosted on Github
• Rubygems page
• Documentation

If you would like to commit a patch, great! Just do the usual github pull request stuff and we'll check it out.

Pathological is licensed under the MIT license.