chef

https://github.com/opscode/chef

Ruby

A systems integration framework, built to bring the benefits of configuration management to your entire infrastructure.

Chef::Property#explicitly_accepts_nil?

Find out whether this type accepts nil explicitly.

A type accepts nil explicitly if "is" allows nil, it validates as nil, *and* is not simply
an empty type.

A type is presumed to accept nil if it does coercion (which must handle nil).

These examples accept nil explicitly:
```ruby
property :a, [ String, nil ]
property :a, [ String, NilClass ]
property :a, [ String, proc { |v| v.nil? } ]
```

This does not (because the "is" doesn't exist or doesn't have nil):

```ruby
property :x, String
```

These do not, even though nil would validate fine (because they do not
have "is"):

```ruby
property :a
property :a, equal_to: [ 1, 2, 3, nil ]
property :a, kind_of: [ String, NilClass ]
property :a, respond_to: [ ]
property :a, callbacks: { "a" => proc { |v| v.nil? } }
```

Source | Google | Stack overflow

Edit

git clone [email protected]:opscode/chef.git
cd chef
open lib/chef/property.rb

Contribute

# Make a new branch
git checkout -b -your-name--update-docs-Chef--Property-explicitly_accepts_nil--for-pr

# Commit to git
git add lib/chef/property.rbgit commit -m "better docs for Chef::Property#explicitly_accepts_nil?"

# Open pull request
gem install hub # on a mac you can `brew install hub`
hub fork
git push <your name> -your-name--update-docs-Chef--Property-explicitly_accepts_nil--for-pr
hub pull-request

# Celebrate!