Allow `truncate` for SQLite3 adapter and add `rails db:seed:replant` (#34779)

* Add `ActiveRecord::Base.connection.truncate` for SQLite3 adapter.

SQLite doesn't support `TRUNCATE TABLE`, but SQLite3 adapter can support
`ActiveRecord::Base.connection.truncate` by using `DELETE FROM`.

`DELETE` without `WHERE` uses "The Truncate Optimization",
see https://www.sqlite.org/lang_delete.html.

* Add `rails db:seed:replant` that truncates database tables and loads the seeds

Closes #34765

2 files changed, 140 insertions, 0 deletions

diff --git a/activerecord/test/cases/adapters/sqlite3/connection_test.rb b/activerecord/test/cases/adapters/sqlite3/connection_test.rb
new file mode 100644
index 0000000000..3dabc8766a
--- /dev/null
+++ b/activerecord/test/cases/adapters/sqlite3/connection_test.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+
+class SQLite3ConnectionTest < ActiveRecord::SQLite3TestCase
+  fixtures :comments
+
+  def test_truncate
+    rows = ActiveRecord::Base.connection.exec_query("select count(*) from comments")
+    count = rows.first.values.first
+    assert_operator count, :>, 0
+
+    ActiveRecord::Base.connection.truncate("comments")
+    rows = ActiveRecord::Base.connection.exec_query("select count(*) from comments")
+    count = rows.first.values.first
+    assert_equal 0, count
+  end
+end
diff --git a/activerecord/test/cases/tasks/database_tasks_test.rb b/activerecord/test/cases/tasks/database_tasks_test.rb
index 3fd1813d64..bd6fb099a4 100644
--- a/activerecord/test/cases/tasks/database_tasks_test.rb
+++ b/activerecord/test/cases/tasks/database_tasks_test.rb
@@ -2,6 +2,7 @@
 
 require "cases/helper"
 require "active_record/tasks/database_tasks"
+require "models/author"
 
 module ActiveRecord
   module DatabaseTasksSetupper
@@ -944,6 +945,127 @@ module ActiveRecord
     end
   end
 
+  unless in_memory_db?
+    class DatabaseTasksTruncateAllTest < ActiveRecord::TestCase
+      self.use_transactional_tests = false
+
+      fixtures :authors, :author_addresses
+
+      def test_truncate_tables
+        assert_operator Author.count, :>, 0
+        assert_operator AuthorAddress.count, :>, 0
+
+        old_configurations = ActiveRecord::Base.configurations
+        configurations = { development: ActiveRecord::Base.configurations["arunit"] }
+        ActiveRecord::Base.configurations = configurations
+
+        ActiveRecord::Tasks::DatabaseTasks.stub(:root, nil) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+
+        assert_equal 0, Author.count
+        assert_equal 0, AuthorAddress.count
+      ensure
+        ActiveRecord::Base.configurations = old_configurations
+      end
+    end
+  end
+
+  class DatabaseTasksTruncateAllWithMultipleDatabasesTest < ActiveRecord::TestCase
+    def setup
+      @configurations = {
+        "development" => { "primary" => { "database" => "dev-db" }, "secondary" => { "database" => "secondary-dev-db" } },
+        "test" => { "primary" => { "database" => "test-db" }, "secondary" => { "database" => "secondary-test-db" } },
+        "production" => { "primary" => { "url" => "abstract://prod-db-host/prod-db" }, "secondary" => { "url" => "abstract://secondary-prod-db-host/secondary-prod-db" } }
+      }
+    end
+
+    def test_truncate_all_databases_for_environment
+      with_stubbed_configurations do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :truncate_tables,
+          [
+            ["database" => "test-db"],
+            ["database" => "secondary-test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("test")
+          )
+        end
+      end
+    end
+
+    def test_truncate_all_databases_with_url_for_environment
+      with_stubbed_configurations do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :truncate_tables,
+          [
+            ["adapter" => "abstract", "database" => "prod-db", "host" => "prod-db-host"],
+            ["adapter" => "abstract", "database" => "secondary-prod-db", "host" => "secondary-prod-db-host"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("production")
+          )
+        end
+      end
+    end
+
+    def test_truncate_all_development_databases_when_env_was_no_specified
+      with_stubbed_configurations do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :truncate_tables,
+          [
+            ["database" => "dev-db"],
+            ["database" => "secondary-dev-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    end
+
+    def test_truncate_all_development_databases_when_env_is_development
+      old_env = ENV["RAILS_ENV"]
+      ENV["RAILS_ENV"] = "development"
+
+      with_stubbed_configurations do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :truncate_tables,
+          [
+            ["database" => "dev-db"],
+            ["database" => "secondary-dev-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    ensure
+      ENV["RAILS_ENV"] = old_env
+    end
+
+    private
+      def with_stubbed_configurations
+        old_configurations = ActiveRecord::Base.configurations
+        ActiveRecord::Base.configurations = @configurations
+
+        yield
+      ensure
+        ActiveRecord::Base.configurations = old_configurations
+      end
+  end
+
   class DatabaseTasksCharsetTest < ActiveRecord::TestCase
     include DatabaseTasksSetupper