Allow specify fixtures to be ignored

Allow specifying what fixtures can be ignored by setting
`ignore` in fixtures YAML file:

    # users.yml
    _fixture:
      ignore:
        - base

    base: &base
      admin: false
      introduction: "This is a default description"

    admin:
      <<: *base
      admin: true

    visitor:
      <<: *base

In the above example, "base" fixture will be ignored when creating
users fixture. This is helpful when you want to inherit attributes
and it makes your fixtures more "DRY".

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Allow specifying fixtures to be ignored by setting `ignore` in YAML file's '_fixture' section.
+
+    *Tongfei Gao*
+
 *   Make the DATABASE_URL env variable only affect the primary connection. Add new env variables for multiple databases.
 
     *John Crepezzi*, *Eileen Uchitelle*

activerecord/lib/active_record/fixture_set/file.rb

@@ -29,6 +29,10 @@ module ActiveRecord
         config_row["model_class"]
       end
 
+      def ignored_fixtures
+        config_row["ignore"]
+      end
+
       private
         def rows
           @rows ||= raw_rows.reject { |fixture_name, _| fixture_name == "_fixture" }
@@ -40,7 +44,7 @@ module ActiveRecord
             if row
               row.last
             else
-              { 'model_class': nil }
+              { 'model_class': nil, 'ignore': nil }
             end
           end
         end

activerecord/lib/active_record/fixtures.rb

@@ -420,6 +420,29 @@ module ActiveRecord
   #
   # Any fixture labeled "DEFAULTS" is safely ignored.
   #
+  # Besides using "DEFAULTS", you can also specify what fixtures will
+  # be ignored by setting "ignore" in "_fixture" section.
+  #
+  #   # users.yml
+  #   _fixture:
+  #     ignore:
+  #       - base
+  #     # or use "ignore: base" when there is only one fixture needs to be ignored.
+  #
+  #   base: &base
+  #     admin: false
+  #     introduction: "This is a default description"
+  #
+  #   admin:
+  #     <<: *base
+  #     admin: true
+  #
+  #   visitor:
+  #     <<: *base
+  #
+  # In the above example, 'base' will be ignored when creating fixtures.
+  # This can be used for common attributes inheriting.
+  #
   # == Configure the fixture model class
   #
   # It's possible to set the fixture's model class directly in the YAML file.
@@ -614,7 +637,7 @@ module ActiveRecord
         end
     end
 
-    attr_reader :table_name, :name, :fixtures, :model_class, :config
+    attr_reader :table_name, :name, :fixtures, :model_class, :ignored_fixtures, :config
 
     def initialize(_, name, class_name, path, config = ActiveRecord::Base)
       @name     = name
@@ -647,8 +670,8 @@ module ActiveRecord
     # Returns a hash of rows to be inserted. The key is the table, the value is
     # a list of rows to insert to that table.
     def table_rows
-      # allow a standard key to be used for doing defaults in YAML
-      fixtures.delete("DEFAULTS")
+      # allow specifying fixtures to be ignored by setting `ignore` in `_fixture` section
+      fixtures.except!(*ignored_fixtures)
 
       TableRows.new(
         table_name,
@@ -667,6 +690,21 @@ module ActiveRecord
         end
       end
 
+      def ignored_fixtures=(base)
+        @ignored_fixtures =
+            case base
+            when Array
+              base
+            when String
+              [base]
+            else
+              []
+            end
+
+        @ignored_fixtures << "DEFAULTS" unless @ignored_fixtures.include?("DEFAULTS")
+        @ignored_fixtures.compact
+      end
+
       # Loads the fixtures from the YAML file at +path+.
       # If the file sets the +model_class+ and current instance value is not set,
       # it uses the file value.
@@ -678,6 +716,7 @@ module ActiveRecord
         yaml_files.each_with_object({}) do |file, fixtures|
           FixtureSet::File.open(file) do |fh|
             self.model_class ||= fh.model_class if fh.model_class
+            self.ignored_fixtures ||= fh.ignored_fixtures
             fh.each do |fixture_name, row|
               fixtures[fixture_name] = ActiveRecord::Fixture.new(row, model_class)
             end

activerecord/test/cases/fixtures_test.rb

@@ -1279,6 +1279,33 @@ class CustomNameForFixtureOrModelTest < ActiveRecord::TestCase
   end
 end
 
+class IgnoreFixturesTest < ActiveRecord::TestCase
+  fixtures :other_books, :parrots
+
+  test "ignores books fixtures" do
+    assert_raise(StandardError) { other_books(:published) }
+    assert_raise(StandardError) { other_books(:published_paperback) }
+    assert_raise(StandardError) { other_books(:published_ebook) }
+
+    assert_equal 2, Book.count
+    assert_equal "Agile Web Development with Rails", other_books(:awdr).name
+    assert_equal "published", other_books(:awdr).status
+    assert_equal "paperback", other_books(:awdr).format
+    assert_equal "english", other_books(:awdr).language
+
+    assert_equal "Ruby for Rails", other_books(:rfr).name
+    assert_equal "ebook", other_books(:rfr).format
+    assert_equal "published", other_books(:rfr).status
+  end
+
+  test "ignores parrots fixtures" do
+    assert_raise(StandardError) { parrots(:DEFAULT) }
+    assert_raise(StandardError) { parrots(:DEAD_PARROT) }
+
+    assert_equal "DeadParrot", parrots(:polly).parrot_sti_class
+  end
+end
+
 class FixturesWithDefaultScopeTest < ActiveRecord::TestCase
   fixtures :bulbs
 

activerecord/test/fixtures/other_books.yml

@@ -0,0 +1,26 @@
+_fixture:
+  model_class: Book
+  ignore:
+    - PUBLISHED
+    - PUBLISHED_PAPERBACK
+    - PUBLISHED_EBOOK
+
+PUBLISHED: &PUBLISHED
+  status: :published
+
+PUBLISHED_PAPERBACK: &PUBLISHED_PAPERBACK
+  <<: *PUBLISHED
+  format: "paperback"
+  language: :english
+
+PUBLISHED_EBOOK: &PUBLISHED_EBOOK
+  <<: *PUBLISHED
+  format: "ebook"
+
+awdr:
+  <<: *PUBLISHED_PAPERBACK
+  name: "Agile Web Development with Rails"
+
+rfr:
+  <<: *PUBLISHED_EBOOK
+  name: "Ruby for Rails"

activerecord/test/fixtures/parrots.yml

@@ -1,3 +1,9 @@
+_fixture:
+  ignore: DEAD_PARROT
+
+DEAD_PARROT: &DEAD_PARROT
+  parrot_sti_class: DeadParrot
+
 george:
   name: "Curious George"
   treasures: diamond, sapphire
@@ -17,7 +23,7 @@ polly:
   name: $LABEL
   killer: blackbeard
   treasures: sapphire, ruby
-  parrot_sti_class: DeadParrot
+  <<: *DEAD_PARROT
 
 DEFAULTS: &DEFAULTS
   treasures: sapphire, ruby