Added new function sprintf_hash to allow using named references

Author: vStone

README.md

@@ -1649,6 +1649,24 @@ Returns the number of elements in a string, an array or a hash. This function wi
 
 *Type*: rvalue.
 
+#### `sprintf_hash`
+
+Perform printf-style formatting with named references of text.
+
+The first paameter is format string describing how the rest of the parameters in the hash
+should be formatted. See the documentation for the `Kernel::sprintf` function in Ruby for
+all the details.
+
+*Example:*
+
+```puppet
+$output = sprintf_hash('String: %<foo>s / number converted to binary: %<number>b',
+                       { 'foo' => 'a string', 'number' => 5 })
+# $output = 'String: a string / number converted to binary: 101'
+```
+
+*Type*: rvalue
+
 #### `sort`
 
 Sorts strings and arrays lexically.

lib/puppet/functions/sprintf_hash.rb

@@ -0,0 +1,28 @@
+# Uses sprintf with named references.
+#
+# The first parameter is format string describing how the rest of the parameters in the hash
+# should be formatted. See the documentation for the `Kernel::sprintf` function in Ruby for
+# all the details.
+#
+# In the given argument hash with parameters, all keys are converted to symbols so they work
+# with the `sprintf` function.
+#
+# @example Format a string and number
+#   $output = sprintf_hash('String: %<foo>s / number converted to binary: %<number>b',
+#                          { 'foo' => 'a string', 'number' => 5 })
+#   # $output = 'String: a string / number converted to binary: 101'
+#
+Puppet::Functions.create_function(:sprintf_hash) do
+  # @param format The format to use.
+  # @param arguments Hash with parameters.
+  # @return The formatted string.
+  dispatch :sprintf_hash do
+    param 'String', :format
+    param 'Hash', :arguments
+    return_type 'String'
+  end
+
+  def sprintf_hash(format, arguments)
+    Kernel.sprintf(format, Hash[arguments.map { |(k, v)| [k.to_sym, v] }])
+  end
+end

spec/functions/sprintf_hash_spec.rb

@@ -0,0 +1,32 @@
+require 'spec_helper'
+
+describe 'sprintf_hash' do
+  it 'exists' do
+    is_expected.not_to eq(nil)
+  end
+
+  context 'validate param count' do
+    it 'fails with no arguments' do
+      is_expected.to run.with_params.and_raise_error(ArgumentError, %r{expects 2 arguments}i)
+    end
+    it 'fails with 1 argument' do
+      is_expected.to run.with_params('').and_raise_error(ArgumentError, %r{expects 2 arguments}i)
+    end
+    it 'fails with too many arguments' do
+      is_expected.to run.with_params('', '', '').and_raise_error(ArgumentError, %r{expects 2 arguments}i)
+    end
+  end
+
+  context 'validate param type' do
+    it 'fails with wrong format type' do
+      is_expected.to run.with_params(false, {}).and_raise_error(ArgumentError, %r{parameter 'format' expects a String value}i)
+    end
+    it 'fails with wrong arguments type' do
+      is_expected.to run.with_params('', false).and_raise_error(ArgumentError, %r{parameter 'arguments' expects a Hash value}i)
+    end
+  end
+
+  it 'prints formats with name placeholders' do
+    is_expected.to run.with_params('string %<foo>s and integer %<bar>b', 'foo' => '_foo_', 'bar' => 5).and_return('string _foo_ and integer 101')
+  end
+end