1 files changed, 100 insertions, 0 deletions
diff --git a/lib/chef/mixin/template.rb b/lib/chef/mixin/template.rb
new file mode 100644
index 0000000000..78148d2577
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+++ b/lib/chef/mixin/template.rb
@@ -0,0 +1,100 @@
+#--
+# Author:: Adam Jacob (<adam@opscode.com>)
+# Copyright:: Copyright (c) 2008 Opscode, Inc.
+# License:: Apache License, Version 2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+#     http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+require 'tempfile'
+require 'erubis'
+
+class Chef
+  module Mixin
+    module Template
+      
+      module ChefContext
+        def node
+          return @node if @node
+          raise "Could not find a value for node. If you are explicitly setting variables in a template, " +
+                "include a node variable if you plan to use it."
+        end
+      end
+      
+      ::Erubis::Context.send(:include, ChefContext)
+      
+      # Render a template with Erubis.  Takes a template as a string, and a 
+      # context hash.  
+      def render_template(template, context)
+        begin
+          eruby = Erubis::Eruby.new(template)
+          output = eruby.evaluate(context)
+        rescue Object => e
+          raise TemplateError.new(e, template, context)
+        end
+        Tempfile.open("chef-rendered-template") do |tempfile|
+          tempfile.print(output)
+          tempfile.close
+          yield tempfile
+        end
+      end
+      
+      class TemplateError < RuntimeError
+        attr_reader :original_exception, :context
+        SOURCE_CONTEXT_WINDOW = 2
+        
+        def initialize(original_exception, template, context)
+          @original_exception, @template, @context = original_exception, template, context
+        end
+        
+        def message
+          @original_exception.message
+        end
+        
+        def line_number
+          @line_number ||= $1.to_i if original_exception.backtrace.find {|line| line =~ /\(erubis\):(\d+)/ }
+        end
+        
+        def source_location
+          "on line ##{line_number}"
+        end
+        
+        def source_listing
+          @source_listing ||= begin
+            lines = @template.split(/\n/)
+            if line_number
+              line_index = line_number - 1
+              beginning_line = line_index <= SOURCE_CONTEXT_WINDOW ? 0 : line_index - SOURCE_CONTEXT_WINDOW
+              source_size = SOURCE_CONTEXT_WINDOW * 2 + 1
+            else
+              beginning_line = 0
+              source_size    = lines.length
+            end
+            contextual_lines = lines[beginning_line, source_size]
+            output = []
+            contextual_lines.each_with_index do |line, index|
+              line_number = (index+beginning_line+1).to_s.rjust(3)
+              output << "#{line_number}: #{line}"
+            end
+            output.join("\n")
+          end
+        end
+        
+        def to_s
+          "\n\n#{self.class} (#{message}) #{source_location}:\n\n" +
+            "#{source_listing}\n\n  #{original_exception.backtrace.join("\n  ")}\n\n"
+        end
+      end
+    end
+  end
+end