Hammer CLI

While working on the hammer cli for katello, I find that we really need the ability in the output format DSL to 'omit' attributes/fields that are nil (or blank).

Below is a scenario to describe why this is needed and useful.

For katello content view filters, a user may create a filter for the following types of content: package, package group, erratum or puppet module.

For each filter that the user creates, the 'parameters' for the filter may vary based upon the filter type, but also based upon what the user wants to define in the filter.

The following output format covers the possibilities:

label "Parameters" do
          from :parameters do
            collection :units, "Units" do
              field :id, "ID" 
              field :name, "Name" 
              field :author, "Author" 
              field :version, "Version" 
              field :min_version, "Minimum Version" 
              field :max_version, "Maximum Version" 
              field :inclusion, "Include" 
              field :created_at, "Created" 
            end

label "Date Range" do
              from :date_range do
                field :start, "Start Date" 
                field :end, "End Date" 
              end
            end

field :inclusion, "Include" 
            field :created_at, "Created" 
          end
        end

For a very simple package rule, to 'include zip 10.0', the command output looks like:

hammer> content_view filter info --id 4
Filter ID: 4
Name: filter1
Type: rpm
Repositories:
Parameters:
Units:
ID:
Name: zip
Author:
Version: 10.0
Minimum Version:
Maximum Version:
Include: true
Created: 2014-01-31T13:48:33Z

Date Range:         
    Start Date:       
    End Date:         
  Include:            
  Created:

As you can see, there are a lot of empty fields.

Given that the filter can contain many different parameter units, we really need the ability to leave out all of the 'empty' fields that are not returned by the server. One possibility would be to specify this in the output format using something like ":include_blank? => false" when defining the output. For example, the above specification could become:

label "Parameters" do
          from :parameters do
            collection :units, "Units", :include_blank? => false do
              field :id, "ID", :include_blank? => false
              field :name, "Name", :include_blank? => false
              field :author, "Author", :include_blank? => false
              field :version, "Version", :include_blank? => false
              field :min_version, "Minimum Version", :include_blank? => false
              field :max_version, "Maximum Version", :include_blank? => false
              field :inclusion, "Include", :include_blank? => false
              field :created_at, "Created", :include_blank? => false
            end

label "Date Range", :include_blank? => false do
              from :date_range do
                field :start, "Start Date", :include_blank? => false
                field :end, "End Date", :include_blank? => false
              end
            end

field :inclusion, "Include" 
            field :created_at, "Created" 
          end
        end

With this, the same command could be streamlined to look like:

hammer> content_view filter info --id 4
Filter ID: 4
Name: filter1
Type: rpm
Repositories:
Parameters:
Units:
Name: zip
Version: 10.0
Include: true
Created: 2014-01-31T13:48:33Z