Lather¶ ↑

• github.com/jbarnette/lather

Lather is an easy way to watch files and do something when they change. By default, it checks for changes every second.

The lather command-line tool lets you quickly track changes to a set of files.

$ lather 'test/**/*_test.rb'

By default, lather will print a message each time a file matching your spec changes. ** is supported for recursive globbing, but make sure to escape/quote the glob so your shell doesn’t expand it.

You can also run a command every time something changes:

$ lather -r 'rake test' '{lib,test}/**/*.rb'

require "lather"

watcher = Lather::Watcher.new "**/*.rb" do |changed|
  puts "Files changed: #{changed.join(' ')}"
end

watcher.go!

If you want to mess with the polling interval:

# :sleep is in seconds
Lather::Watcher.new "*.rb", :sleep => 5

require "rake/lathertask"

Rake::LatherTask.new "lib/**/*.rb" do |l|
  l.target = :something
  l.globs << "ext/**/*.{c,h}"
end

This creates a lather task, which will call the target task any time the globs change. The block is optional: target defaults to :test.

If target is set to an instance of Rake::TestTask, some special behavior is enabled: Lather will add the test task’s file list to globs, and will set the TEST environment variable to the list of tests that need to be run.

require "rake/testtask"
require "rake/lathertask"

test = Rake::TestTask.new do |t|
  t.libs << "test"
  t.pattern = "test/**/*_test.rb"
end

Rake::LatherTask.new "lib/**/*.rb", :target => test

The heuristic is really simple: If lib/foo.rb changes, any test whose path contains ‘foo` will be run. There’s no tracking of failures or single test runs. If you want more than this, you should be using Autotest.

$ gem install lather

• A way to get at the list of changed files in a -r command.

• Some default exclude (like backup/editor files, .svn, .git) patterns, and an easy way to add new ones.

• A --sleep <secs> switch for the command-line tool.

Lather owes a huge debt to Ryan Davis’ ZenTest library, specifically autotest. Use it. See also Mike Clark and Geoffrey Grosenbach’s rstakeout, and a bunch of similar I’ve forgotten.

Copyright 2009 John Barnette (jbarnette@rubyforge.org)

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