What's the benefit of version.rb in Ruby gem

Question

It is common to have a version.rb file, defining the version of the gem, like:

module Foo
  VERSION = "0.0.1"
end

and in the .gemspec file, require the version.rb and use Foo::VERSION there.

What is the benefit of this convention?

--

Also, sometime when namespace is used, the generated verison file can be deeply in nested folders. Wouldn't it be easier to place a version.rb directly under lib/ and specifying the version there?

Answer 1

This is done this way to reduce churn (change rate) on .gemspec file. I imagine that dependency changes are much more important than version bumps (which are also more frequent). So version changes would add too much noise and hide important commits.

Answer 2

It depends on what gem builder you used. Having a separate file makes it easy to stomp and rebuild as you bump version numbers with rake tasks, for example. this is a lot easier than fiddling with a source file and trying not to damage anything.

Some packagers use a separate VERSION file.

Answer 3

In short, if your gem doesn't need to know the current version itself, then you don't need a version.rb. Even some of the well-known gems like rack don't use it.

Let's say you are building an executable gem that contains an option -v to see the current version, or you have to print current version to warn developers there are some deprecated changes, then to require a separated version file is much more convenient and efficient than parse the gemspec.

It's just a convention in Ruby community. The main reason of why version.rb is everywhere is that lots of gems are built by bundler gem.