Add CreateMigration action

This Thor-action isolates the logic whether to (over-)write migration and
what is shown to the user. It's modelled after Thor's CreateFile-action.

This solves the issue that removing a non-existing migration, tried to
remove the template-path (#13588).

Related issues: #12674

1 files changed, 134 insertions, 0 deletions

diff --git a/railties/test/generators/create_migration_test.rb b/railties/test/generators/create_migration_test.rb
new file mode 100644
index 0000000000..e16a77479a
--- /dev/null
+++ b/railties/test/generators/create_migration_test.rb
@@ -0,0 +1,134 @@
+require 'generators/generators_test_helper'
+require 'rails/generators/rails/migration/migration_generator'
+
+class CreateMigrationTest < Rails::Generators::TestCase
+  include GeneratorsTestHelper
+
+  class Migrator < Rails::Generators::MigrationGenerator
+    include Rails::Generators::Migration
+
+    def self.next_migration_number(dirname)
+      current_migration_number(dirname) + 1
+    end
+  end
+
+  tests Migrator
+
+  def default_destination_path
+    "db/migrate/create_articles.rb"
+  end
+
+  def create_migration(destination_path = default_destination_path, config = {}, generator_options = {}, &block)
+    migration_name = File.basename(destination_path, '.rb')
+    generator([migration_name], generator_options)
+    generator.set_migration_assigns!(destination_path)
+
+    dir, base = File.split(destination_path)
+    timestamped_destination_path = File.join(dir, ["%migration_number%", base].join('_'))
+
+    @migration = Rails::Generators::Actions::CreateMigration.new(generator, timestamped_destination_path, block || "contents", config)
+  end
+
+  def migration_exists!(*args)
+    @existing_migration = create_migration(*args)
+    invoke!
+    @generator = nil
+  end
+
+  def invoke!
+    capture(:stdout) { @migration.invoke! }
+  end
+
+  def revoke!
+    capture(:stdout) { @migration.revoke! }
+  end
+
+  def test_invoke
+    create_migration
+
+    assert_match(/create  db\/migrate\/1_create_articles.rb\n/, invoke!)
+    assert_file @migration.destination
+  end
+
+  def test_invoke_pretended
+    create_migration(default_destination_path, {}, { pretend: true })
+
+    assert_no_file @migration.destination
+  end
+
+  def test_invoke_when_exists
+    migration_exists!
+    create_migration
+
+    assert_equal @existing_migration.destination, @migration.existing_migration
+  end
+
+  def test_invoke_when_exists_identical
+    migration_exists!
+    create_migration
+
+    assert_match(/identical  db\/migrate\/1_create_articles.rb\n/, invoke!)
+    assert @migration.identical?
+  end
+
+  def test_invoke_when_exists_not_identical
+    migration_exists!
+    create_migration { "different content" }
+
+    assert_raise(Rails::Generators::Error) { invoke! }
+  end
+
+  def test_invoke_forced_when_exists_not_identical
+    dest = "db/migrate/migration.rb"
+    migration_exists!(dest)
+    create_migration(dest, force: true) { "different content" }
+
+    stdout = invoke!
+    assert_match(/remove  db\/migrate\/1_migration.rb\n/, stdout)
+    assert_match(/create  db\/migrate\/2_migration.rb\n/, stdout)
+    assert_file @migration.destination
+    assert_no_file @existing_migration.destination
+  end
+
+  def test_invoke_forced_pretended_when_exists_not_identical
+    migration_exists!
+    create_migration(default_destination_path, { force: true }, { pretend: true }) do
+      "different content"
+    end
+
+    stdout = invoke!
+    assert_match(/remove  db\/migrate\/1_create_articles.rb\n/, stdout)
+    assert_match(/create  db\/migrate\/2_create_articles.rb\n/, stdout)
+    assert_no_file @migration.destination
+  end
+
+  def test_invoke_skipped_when_exists_not_identical
+    migration_exists!
+    create_migration(default_destination_path, {}, { skip: true }) { "different content" }
+
+    assert_match(/skip  db\/migrate\/2_create_articles.rb\n/, invoke!)
+    assert_no_file @migration.destination
+  end
+
+  def test_revoke
+    migration_exists!
+    create_migration
+
+    assert_match(/remove  db\/migrate\/1_create_articles.rb\n/, revoke!)
+    assert_no_file @existing_migration.destination
+  end
+
+  def test_revoke_pretended
+    migration_exists!
+    create_migration(default_destination_path, {}, { pretend: true })
+
+    assert_match(/remove  db\/migrate\/1_create_articles.rb\n/, revoke!)
+    assert_file @existing_migration.destination
+  end
+
+  def test_revoke_when_no_exists
+    create_migration
+
+    assert_match(/remove  db\/migrate\/1_create_articles.rb\n/, revoke!)
+  end
+end