Add a `knife yaml convert` tool

Very basic interface, reads in a YAML recipe, ruby recipe goes to stdout.

```
---
resources:

  - type: "bash"
    name: "new chef user"
    code: "
    touch /tmp/jmc/something ;
    echo something >> /tmp/jmc/something ;
    rm -f /tmp/jmc/bash ;
    "

something:
  - other: "dont use this"
```

gets converted to:

```

bash "new chef user" do
  code " touch /tmp/jmc/something ; echo something >> /tmp/jmc/something ; rm -f /tmp/jmc/bash ; "
end
```

Signed-off-by: Bryan McLellan <btm@loftninjas.org>

1 files changed, 67 insertions, 0 deletions

diff --git a/lib/chef/knife/yaml_convert.rb b/lib/chef/knife/yaml_convert.rb
new file mode 100644
index 0000000000..5cdc340d22
--- /dev/null
+++ b/lib/chef/knife/yaml_convert.rb
@@ -0,0 +1,67 @@
+#
+# Author:: Bryan McLellan <btm@loftninjas.org>
+# Copyright:: Copyright 2020, Chef Software 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 "yaml"
+require_relative "../knife"
+class Chef::Knife::YamlConvert < Chef::Knife
+
+  banner "knife yaml convert YAML_FILENAME"
+
+  def run
+    if name_args.empty?
+      ui.error("Please specify the file name of a YAML recipe to convert to Ruby")
+      exit 1
+    elsif name_args.size >= 2
+      ui.error("Only one recipe may converted at a time")
+      exit 1
+    end
+
+    filename = @name_args[0]
+    yaml_contents = IO.read(filename)
+
+    if ::YAML.load_stream(yaml_contents).length > 1
+      raise ArgumentError, "YAML recipe '#{filename}' contains multiple documents, only one is supported"
+    end
+
+    # Unfortunately, per the YAML spec, comments are stripped when we load, so we lose them on conversion
+    yaml_hash = ::YAML.safe_load(yaml_contents)
+    unless yaml_hash.is_a?(Hash) && yaml_hash.key?("resources")
+      raise ArgumentError, "YAML recipe '#{source_file}' must contain a top-level 'resources' hash (YAML sequence), i.e. 'resources:'"
+    end
+
+    ruby_contents = []
+    ruby_contents << "# Autoconverted recipe from #{filename}"
+    ruby_contents << ""
+
+    yaml_hash["resources"].each do |r|
+      type = r.delete("type")
+      name = r.delete("name")
+
+      ruby_contents << "#{type} \"#{name}\" do"
+      r.each do |p|
+        ruby_contents << "  #{p.shift} \"#{p.shift}\""
+      end
+      ruby_contents << "end"
+      ruby_contents << ""
+    end
+
+    ruby_contents.each do |l|
+      puts l
+    end
+  end
+end