(MODULES-2516) Adds an is_a() function

The data type system is very hard to understand. Many people don't
understand why

    type_of([1,2,3]) == Array

will fail, but

    type_of([1,2,3]) <= Array

passes. This does a simpler validation that doesn't rely on explicit
data types. Instead, use

    $foo = [1,2,3]
    if $foo.is_a(Array) {
      notify { 'This is an array': }
    }

This is based on code by Ben Ford <ben.ford@puppetlabs.com>.

  * Added acceptance tests
  * Added dispatch
  * Improved unit tests
  * Added docs to README

2 files changed, 28 insertions, 1 deletions

diff --git a/spec/functions/is_a_spec.rb b/spec/functions/is_a_spec.rb
new file mode 100644
index 0000000..8dec13f
--- /dev/null
+++ b/spec/functions/is_a_spec.rb
@@ -0,0 +1,25 @@
+require 'spec_helper'
+
+if ENV["FUTURE_PARSER"] == 'yes'
+  describe 'type_of' do
+    pending 'teach rspec-puppet to load future-only functions under 3.7.5' do
+      it { is_expected.not_to eq(nil) }
+    end
+  end
+end
+
+if Puppet.version.to_f >= 4.0
+  describe 'is_a' do
+    it { is_expected.not_to eq(nil) }
+    it { is_expected.to run.with_params().and_raise_error(ArgumentError) }
+    it { is_expected.to run.with_params('', '').and_raise_error(ArgumentError) }
+
+    it 'succeeds when comparing a string and a string' do
+      is_expected.to run.with_params('hello world', String).and_return(true)
+    end
+
+    it 'fails when comparing an integer and a string' do
+      is_expected.to run.with_params(5, String).and_return(false)
+    end
+  end
+end
diff --git a/spec/functions/type_of_spec.rb b/spec/functions/type_of_spec.rb
index f770990..cc9ef78 100644
--- a/spec/functions/type_of_spec.rb
+++ b/spec/functions/type_of_spec.rb
@@ -2,7 +2,9 @@ require 'spec_helper'
 
 if ENV["FUTURE_PARSER"] == 'yes'
   describe 'type_of' do
-    pending 'teach rspec-puppet to load future-only functions under 3.7.5'
+    pending 'teach rspec-puppet to load future-only functions under 3.7.5' do
+      it { is_expected.not_to eq(nil) }
+    end
   end
 end