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.

4 files changed, 80 insertions, 4 deletions

diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 1ccdfb6589..5e2b82c3e9 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Add a `required` option to the model generator for associations
+
+    *Sean Griffin*
+
 *   Add `after_bundle` callbacks in Rails templates. Useful for allowing the
     generated binstubs to be added to version control.
 
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
diff --git a/railties/test/generators/migration_generator_test.rb b/railties/test/generators/migration_generator_test.rb
index 6fac643ed0..72f5fe29ca 100644
--- a/railties/test/generators/migration_generator_test.rb
+++ b/railties/test/generators/migration_generator_test.rb
@@ -159,6 +159,18 @@ class MigrationGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_add_migration_with_required_references
+    migration = "add_references_to_books"
+    run_generator [migration, "author:belongs_to{required}", "distributor:references{polymorphic,required}"]
+
+    assert_migration "db/migrate/#{migration}.rb" do |content|
+      assert_method :change, content do |change|
+        assert_match(/add_reference :books, :author, index: true, null: false/, change)
+        assert_match(/add_reference :books, :distributor, polymorphic: true, index: true, null: false/, change)
+      end
+    end
+  end
+
   def test_create_join_table_migration
     migration = "add_media_join_table"
     run_generator [migration, "artist_id", "musics:uniq"]
diff --git a/railties/test/generators/model_generator_test.rb b/railties/test/generators/model_generator_test.rb
index b67cf02d7b..8e5b556a7d 100644
--- a/railties/test/generators/model_generator_test.rb
+++ b/railties/test/generators/model_generator_test.rb
@@ -1,5 +1,6 @@
 require 'generators/generators_test_helper'
 require 'rails/generators/rails/model/model_generator'
+require 'active_support/core_ext/string/strip'
 
 class ModelGeneratorTest < Rails::Generators::TestCase
   include GeneratorsTestHelper
@@ -363,6 +364,49 @@ class ModelGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_required_belongs_to_adds_required_association
+    run_generator ["account", "supplier:references{required}"]
+
+    expected_file = <<-FILE.strip_heredoc
+    class Account < ActiveRecord::Base
+      belongs_to :supplier, required: true
+    end
+    FILE
+    assert_file "app/models/account.rb", expected_file
+  end
+
+  def test_required_polymorphic_belongs_to_generages_correct_model
+    run_generator ["account", "supplier:references{required,polymorphic}"]
+
+    expected_file = <<-FILE.strip_heredoc
+    class Account < ActiveRecord::Base
+      belongs_to :supplier, polymorphic: true, required: true
+    end
+    FILE
+    assert_file "app/models/account.rb", expected_file
+  end
+
+  def test_required_and_polymorphic_are_order_independent
+    run_generator ["account", "supplier:references{polymorphic.required}"]
+
+    expected_file = <<-FILE.strip_heredoc
+    class Account < ActiveRecord::Base
+      belongs_to :supplier, polymorphic: true, required: true
+    end
+    FILE
+    assert_file "app/models/account.rb", expected_file
+  end
+
+  def test_required_adds_null_false_to_column
+    run_generator ["account", "supplier:references{required}"]
+
+    assert_migration "db/migrate/create_accounts.rb" do |m|
+      assert_method :change, m do |up|
+        assert_match(/t\.references :supplier,.*\snull: false/, up)
+      end
+    end
+  end
+
   private
     def assert_generated_fixture(path, parsed_contents)
       fixture_file = File.new File.expand_path(path, destination_root)