Add a `required` option to the model generator

Syntax was chosen to follow the passing of multiple options to
decimal/numeric types. Curly braces, and allowing any of `,`, `.`, or
`-` to be used as a separator to avoid the need for shell quoting. (I'm
intending to expand this to all columns, but that's another PR.

The `required` option will cause 2 things to change. `required: true`
will be added to the association. `null: false` will be added to the
column in the migration.

1 files changed, 20 insertions, 4 deletions

diff --git a/railties/lib/rails/generators/generated_attribute.rb b/railties/lib/rails/generators/generated_attribute.rb
index c5326d70d1..f16bd8e082 100644
--- a/railties/lib/rails/generators/generated_attribute.rb
+++ b/railties/lib/rails/generators/generated_attribute.rb
@@ -44,8 +44,11 @@ module Rails
             return $1, limit: $2.to_i
           when /decimal\{(\d+)[,.-](\d+)\}/
             return :decimal, precision: $1.to_i, scale: $2.to_i
-          when /(references|belongs_to)\{polymorphic\}/
-            return $1, polymorphic: true
+          when /(references|belongs_to)\{(.+)\}/
+            type = $1
+            provided_options = $2.split(/[,.-]/)
+            options = Hash[provided_options.map { |opt| [opt.to_sym, true] }]
+            return type, options
           else
             return type, {}
           end
@@ -123,7 +126,11 @@ module Rails
       end
 
       def polymorphic?
-        self.attr_options.has_key?(:polymorphic)
+        self.attr_options[:polymorphic]
+      end
+
+      def required?
+        self.attr_options[:required]
       end
 
       def has_index?
@@ -139,12 +146,21 @@ module Rails
       end
 
       def inject_options
-        "".tap { |s| @attr_options.each { |k,v| s << ", #{k}: #{v.inspect}" } }
+        "".tap { |s| options_for_migration.each { |k,v| s << ", #{k}: #{v.inspect}" } }
       end
 
       def inject_index_options
         has_uniq_index? ? ", unique: true" : ""
       end
+
+      def options_for_migration
+        @attr_options.dup.tap do |options|
+          if required?
+            options.delete(:required)
+            options[:null] = false
+          end
+        end
+      end
     end
   end
 end