Ignore test env in DatabaseTasks when DATABASE_URL is present

Fixes https://github.com/rails/rails/issues/28827.

The steps to reproduce are as follows:

git clone git@github.com:bbuchalter/rails-issue-28827.git
cd rails-issue-28827
bundle install
bin/rails db:create

Observe that we create two databases when invoking db:create: development and test. Now observe what happens when we invoke our drop command while using DATABASE_URL.

DATABASE_URL=sqlite3://$(pwd)/db/database_url.sqlite3 bin/rails db:create

As expected, the development environment now uses the DATABASE_URL. What is unexpected is that the test environment does not.

It's unclear what the expected behavior should be in this case, but the cause of it is this: https://github.com/rails/rails/blob/9f2c74eda07ea5a9e4e624d5575a717714088dbf/activerecord/lib/active_record/tasks/database_tasks.rb#L494

Because of each_local_configuration, there seems to be no way invoke these database rake on only the development environment to ensure DATABASE_URL is respected.

The smallest scope of change I can think to make would be to conditionalize this behavior so it does not get applied when DATABASE_URL is present.

activerecord/CHANGELOG.md

+*   Skip test database when running `db:create` or `db:drop` in development
+    with `DATABASE_URL` set.
+
+    *Brian Buchalter*
+
 *   Don't allow mutations on the datbase configurations hash.
 
     Freeze the configurations hash to disallow directly changing the configurations hash. If applications need to change the hash, for example to create adatabases for parallelization, they should use the `DatabaseConfig` object directly.

activerecord/lib/active_record/railties/databases.rake

@@ -34,7 +34,7 @@ db_namespace = namespace :db do
     end
   end
 
-  desc "Creates the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:create:all to create all databases in the config). Without RAILS_ENV or when RAILS_ENV is development, it defaults to creating the development and test databases."
+  desc "Creates the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:create:all to create all databases in the config). Without RAILS_ENV or when RAILS_ENV is development, it defaults to creating the development and test databases, except when DATABASE_URL is present."
   task create: [:load_config] do
     ActiveRecord::Tasks::DatabaseTasks.create_current
   end
@@ -53,7 +53,7 @@ db_namespace = namespace :db do
     end
   end
 
-  desc "Drops the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:drop:all to drop all databases in the config). Without RAILS_ENV or when RAILS_ENV is development, it defaults to dropping the development and test databases."
+  desc "Drops the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:drop:all to drop all databases in the config). Without RAILS_ENV or when RAILS_ENV is development, it defaults to dropping the development and test databases, except when DATABASE_URL is present."
   task drop: [:load_config, :check_protected_environments] do
     db_namespace["drop:_unsafe"].invoke
   end
@@ -73,7 +73,7 @@ db_namespace = namespace :db do
     ActiveRecord::Tasks::DatabaseTasks.truncate_all
   end
 
-  # desc "Empty the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:purge:all to purge all databases in the config). Without RAILS_ENV it defaults to purging the development and test databases."
+  # desc "Empty the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:purge:all to purge all databases in the config). Without RAILS_ENV it defaults to purging the development and test databases, except when DATABASE_URL is present."
   task purge: [:load_config, :check_protected_environments] do
     ActiveRecord::Tasks::DatabaseTasks.purge_current
   end

activerecord/lib/active_record/tasks/database_tasks.rb

@@ -484,7 +484,7 @@ def class_for_adapter(adapter)
 
         def each_current_configuration(environment, spec_name = nil)
           environments = [environment]
-          environments << "test" if environment == "development"
+          environments << "test" if environment == "development" && !ENV["DATABASE_URL"]
 
           environments.each do |env|
             ActiveRecord::Base.configurations.configs_for(env_name: env).each do |db_config|

railties/test/application/rake/dbs_test.rb

@@ -60,6 +60,28 @@ def db_create_with_warning(expected_database)
         db_create_and_drop database_url_db_name
       end
 
+      test "db:create and db:drop with database URL don't use YAML DBs" do
+        require "#{app_path}/config/environment"
+        set_database_url
+
+        File.write("#{app_path}/config/database.yml", <<~YAML)
+          test:
+            adapter: sqlite3
+            database: db/test.sqlite3
+
+          development:
+            adapter: sqlite3
+            database: db/development.sqlite3
+        YAML
+
+        with_rails_env "development" do
+          db_create_and_drop database_url_db_name do
+            assert_not File.exist?("#{app_path}/db/test.sqlite3")
+            assert_not File.exist?("#{app_path}/db/development.sqlite3")
+          end
+        end
+      end
+
       test "db:create and db:drop respect environment setting" do
         app_file "config/database.yml", <<-YAML
           <% 1 %>