Adds support for foreign key annotations

README.rdoc

@@ -175,6 +175,7 @@ you can do so with a simple environment variable, instead of editing the
         -v, --version                    Show the current version of this gem
         -m, --show-migration             Include the migration version number in the annotation
         -i, --show-indexes               List the table's database indexes in the annotation
+        -k, --show-foreign-keys          List the table's foreign key constraints in the annotation
         -s, --simple-indexes             Concat the column's related indexes in the annotation
             --model-dir dir              Annotate model files stored in dir rather than app/models, separate multiple dirs with comas
             --ignore-model-subdirects    Ignore subdirectories of the models directory

bin/annotate

@@ -109,6 +109,11 @@ OptionParser.new do |opts|
     ENV['include_version'] = "yes"
   end
 
+  opts.on('-k', '--show-foreign-keys',
+          "List the table's foreign key constraints in the annotation") do
+    ENV['show_foreign_keys'] = "yes"
+  end
+
   opts.on('-i', '--show-indexes',
           "List the table's database indexes in the annotation") do
     ENV['show_indexes'] = "yes"

lib/annotate.rb

@@ -26,7 +26,7 @@ module Annotate
     :show_indexes, :simple_indexes, :include_version, :exclude_tests,
     :exclude_fixtures, :exclude_factories, :ignore_model_sub_dir,
     :format_bare, :format_rdoc, :format_markdown, :sort, :force, :trace,
-    :timestamp, :exclude_serializers, :classified_sort
+    :timestamp, :exclude_serializers, :classified_sort, :show_foreign_keys,
   ]
   OTHER_OPTIONS=[
     :ignore_columns

lib/annotate/annotate_models.rb

@@ -193,6 +193,10 @@ module AnnotateModels
         info << get_index_info(klass, options)
       end
 
+      if options[:show_foreign_keys] && klass.table_exists?
+        info << get_foreign_key_info(klass, options)
+      end
+
       if options[:format_rdoc]
         info << "#--\n"
         info << "# #{END_MARK}\n"
@@ -223,6 +227,28 @@ module AnnotateModels
       return index_info
     end
 
+    def get_foreign_key_info(klass, options={})
+      if(options[:format_markdown])
+        fk_info = "#\n# ### Foreign Keys\n#\n"
+      else
+        fk_info = "#\n# Foreign Keys\n#\n"
+      end
+
+      foreign_keys = klass.connection.respond_to?(:foreign_keys) ? klass.connection.foreign_keys(klass.table_name) : []
+      return "" if foreign_keys.empty?
+
+      max_size = foreign_keys.collect{|fk| fk.name.size}.max + 1
+      foreign_keys.sort_by{|fk| fk.name}.each do |fk|
+        ref_info = "#{fk.column} => #{fk.to_table}.#{fk.primary_key}"
+        if(options[:format_markdown])
+          fk_info << sprintf("# * `%s`:\n#     * **`%s`**\n", fk.name, ref_info)
+        else
+          fk_info << sprintf("#  %-#{max_size}.#{max_size}s %s", fk.name, "(#{ref_info})").rstrip + "\n"
+        end
+      end
+      return fk_info
+    end
+
     # Add a schema block to a file. If the file already contains
     # a schema info block (a comment starting with "== Schema Information"), check if it
     # matches the block that is already there. If so, leave it be. If not, remove the old

lib/generators/annotate/templates/auto_annotate_models.rake

@@ -11,6 +11,7 @@ if Rails.env.development?
       'position_in_test'     => "before",
       'position_in_fixture'  => "before",
       'position_in_factory'  => "before",
+      'show_foreign_keys'    => "true",
       'show_indexes'         => "true",
       'simple_indexes'       => "false",
       'model_dir'            => "app/models",

spec/annotate/annotate_models_spec.rb

@@ -4,9 +4,26 @@ require 'annotate/annotate_models'
 require 'annotate/active_record_patch'
 
 describe AnnotateModels do
-  def mock_class(table_name, primary_key, columns)
+  def mock_foreign_key(name, from_column, to_table, to_column = 'id')
+    double("ForeignKeyDefinition",
+      :name         => name,
+      :column       => from_column,
+      :to_table     => to_table,
+      :primary_key  => to_column,
+    )
+  end
+
+  def mock_connection(indexes = [], foreign_keys = [])
+    double("Conn",
+      :indexes      => indexes,
+      :foreign_keys => foreign_keys,
+    )
+  end
+
+  def mock_class(table_name, primary_key, columns, foreign_keys = [])
     options = {
-      :connection   => double("Conn", :indexes => []),
+      :connection       => mock_connection([], foreign_keys),
+      :table_exists?    => true,
       :table_name       => table_name,
       :primary_key      => primary_key,
       :column_names     => columns.map { |col| col.name.to_s },
@@ -127,6 +144,33 @@ EOS
 EOS
   end
 
+  it "should get foreign key info" do
+           klass = mock_class(:users, :id, [
+              mock_column(:id, :integer),
+              mock_column(:foreign_thing_id, :integer),
+            ],
+            [
+              mock_foreign_key(
+                'fk_rails_02e851e3b7',
+                'foreign_thing_id',
+                'foreign_things'
+              )
+            ])
+            expect(AnnotateModels.get_schema_info(klass, "Schema Info", :show_foreign_keys => true)).to eql(<<-EOS)
+# Schema Info
+#
+# Table name: users
+#
+#  id               :integer          not null, primary key
+#  foreign_thing_id :integer          not null
+#
+# Foreign Keys
+#
+#  fk_rails_02e851e3b7  (foreign_thing_id => foreign_things.id)
+#
+EOS
+  end
+
   it "should get schema info as RDoc" do
     klass = mock_class(:users, :id, [
                                      mock_column(:id, :integer),

spec/integration/rails_4.1.1/lib/tasks/auto_annotate_models.rake

@@ -11,6 +11,7 @@ if Rails.env.development?
       'position_in_test'     => "before",
       'position_in_fixture'  => "before",
       'position_in_factory'  => "before",
+      'show_foreign_keys'    => "true",
       'show_indexes'         => "true",
       'simple_indexes'       => "false",
       'model_dir'            => "app/models",

spec/integration/rails_4.2.0/lib/tasks/auto_annotate_models.rake

@@ -11,6 +11,7 @@ if Rails.env.development?
       'position_in_test'     => "before",
       'position_in_fixture'  => "before",
       'position_in_factory'  => "before",
+      'show_foreign_keys'    => "true",
       'show_indexes'         => "true",
       'simple_indexes'       => "false",
       'model_dir'            => "app/models",