Allow schema cache path to be defined in the config file

This updates the database tasks for dumping the Active Record schema cache as
well as clearing the schema cache file, allowing the path to be defined in the
database configuration YAML file.

As before, the value can also be defined in an ENV variable, though this would
not work for a multi-db application. If the value is specified neither in the
DB config, nor in the ENV, then the path will continue to be derived from the
DB config spec_name.

Note that in order to make this change cleaner I also moved a bit of logic
out of a rake task and into the DatabaseTasks class, for symmetry.

We have two rake tasks for the schema cache:

    $ rake db:schema:cache:dump
    $ rake db:schema:cache:clear

The cache:dump task was implemented in DatabaseTasks, but the
cache:clear one was not.

I also added some tests for the behavior that I was changing, since some of
the code paths weren't tested.

activerecord/CHANGELOG.md

+*   Allow schema cache path to be defined in the database configuration file.
+
+    For example:
+
+    ```
+    development:
+      adapter: postgresql
+      database: blog_development
+      pool: 5
+      schema_cache_path: tmp/schema/main.yml
+    ```
+
+    *Katrina Owen*
+
 *   Deprecate `#remove_connection` in favor of `#remove_connection_pool` when called on the handler.
 
     `#remove_connection` is deprecated in order to support returning a `DatabaseConfig` object instead of a `Hash`. Use `#remove_connection_pool`, `#remove_connection` will be removed in 6.2.

activerecord/lib/active_record/database_configurations/database_config.rb

@@ -65,6 +65,10 @@ def migrations_paths
       def for_current_env?
         env_name == ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
       end
+
+      def schema_cache_path
+        raise NotImplementedError
+      end
     end
   end
 end

activerecord/lib/active_record/database_configurations/hash_config.rb

@@ -87,6 +87,13 @@ def idle_timeout
       def adapter
         configuration_hash[:adapter]
       end
+
+      # The path to the schema cache dump file for a database.
+      # If omitted, the filename will be read from ENV or a
+      # default will be derived.
+      def schema_cache_path
+        configuration_hash[:schema_cache_path]
+      end
     end
   end
 end

activerecord/lib/active_record/railties/databases.rake

@@ -407,7 +407,10 @@ db_namespace = namespace :db do
       task dump: :load_config do
         ActiveRecord::Base.configurations.configs_for(env_name: ActiveRecord::Tasks::DatabaseTasks.env).each do |db_config|
           ActiveRecord::Base.establish_connection(db_config)
-          filename = ActiveRecord::Tasks::DatabaseTasks.cache_dump_filename(db_config.spec_name)
+          filename = ActiveRecord::Tasks::DatabaseTasks.cache_dump_filename(
+            db_config.spec_name,
+            schema_cache_path: db_config.schema_cache_path,
+          )
           ActiveRecord::Tasks::DatabaseTasks.dump_schema_cache(
             ActiveRecord::Base.connection,
             filename,
@@ -418,8 +421,13 @@ db_namespace = namespace :db do
       desc "Clears a db/schema_cache.yml file."
       task clear: :load_config do
         ActiveRecord::Base.configurations.configs_for(env_name: ActiveRecord::Tasks::DatabaseTasks.env).each do |db_config|
-          filename = ActiveRecord::Tasks::DatabaseTasks.cache_dump_filename(db_config.spec_name)
-          rm_f filename, verbose: false
+          filename = ActiveRecord::Tasks::DatabaseTasks.cache_dump_filename(
+            db_config.spec_name,
+            schema_cache_path: db_config.schema_cache_path,
+          )
+          ActiveRecord::Tasks::DatabaseTasks.clear_schema_cache(
+            filename,
+          )
         end
       end
     end

activerecord/lib/active_record/tasks/database_tasks.rb

@@ -409,14 +409,14 @@ def dump_filename(namespace, format = ActiveRecord::Base.schema_format)
         ENV["SCHEMA"] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, filename)
       end
 
-      def cache_dump_filename(namespace)
+      def cache_dump_filename(namespace, schema_cache_path: nil)
         filename = if namespace == "primary"
           "schema_cache.yml"
         else
           "#{namespace}_schema_cache.yml"
         end
 
-        ENV["SCHEMA_CACHE"] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, filename)
+        schema_cache_path || ENV["SCHEMA_CACHE"] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, filename)
       end
 
       def load_schema_current(format = ActiveRecord::Base.schema_format, file = nil, environment = env)
@@ -454,6 +454,10 @@ def dump_schema_cache(conn, filename)
         open(filename, "wb") { |f| f.write(YAML.dump(conn.schema_cache)) }
       end
 
+      def clear_schema_cache(filename)
+        FileUtils.rm_f filename, verbose: false
+      end
+
       private
         def resolve_configuration(configuration)
           Base.configurations.resolve(configuration)

activerecord/test/cases/tasks/database_tasks_test.rb

@@ -208,12 +208,78 @@ class DatabaseTasksCreateTest < ActiveRecord::TestCase
 
   class DatabaseTasksDumpSchemaCacheTest < ActiveRecord::TestCase
     def test_dump_schema_cache
-      path = "/tmp/my_schema_cache.yml"
-      ActiveRecord::Tasks::DatabaseTasks.dump_schema_cache(ActiveRecord::Base.connection, path)
-      assert File.file?(path)
+      Dir.mktmpdir do |dir|
+        ActiveRecord::Tasks::DatabaseTasks.stub(:db_dir, dir) do
+          path = File.join(dir, "schema_cache.yml")
+          assert_not File.file?(path)
+          ActiveRecord::Tasks::DatabaseTasks.dump_schema_cache(ActiveRecord::Base.connection, path)
+          assert File.file?(path)
+        end
+      end
     ensure
       ActiveRecord::Base.clear_cache!
-      FileUtils.rm_rf(path)
+    end
+
+    def test_clear_schema_cache
+      Dir.mktmpdir do |dir|
+        ActiveRecord::Tasks::DatabaseTasks.stub(:db_dir, dir) do
+          path = File.join(dir, "schema_cache.yml")
+          File.open(path, "wb") do |f|
+            f.puts "This is a cache."
+          end
+          assert File.file?(path)
+          ActiveRecord::Tasks::DatabaseTasks.clear_schema_cache(path)
+          assert_not File.file?(path)
+        end
+      end
+    end
+
+    def test_cache_dump_default_filename
+      old_path = ENV["SCHEMA_CACHE"]
+      ENV.delete("SCHEMA_CACHE")
+
+      ActiveRecord::Tasks::DatabaseTasks.stub(:db_dir, "db") do
+        path = ActiveRecord::Tasks::DatabaseTasks.cache_dump_filename("primary")
+        assert_equal "db/schema_cache.yml", path
+      end
+    ensure
+      ENV["SCHEMA_CACHE"] = old_path
+    end
+
+    def test_cache_dump_alternate_filename
+      old_path = ENV["SCHEMA_CACHE"]
+      ENV.delete("SCHEMA_CACHE")
+
+      ActiveRecord::Tasks::DatabaseTasks.stub(:db_dir, "db") do
+        path = ActiveRecord::Tasks::DatabaseTasks.cache_dump_filename("alternate")
+        assert_equal "db/alternate_schema_cache.yml", path
+      end
+    ensure
+      ENV["SCHEMA_CACHE"] = old_path
+    end
+
+    def test_cache_dump_filename_with_env_override
+      old_path = ENV["SCHEMA_CACHE"]
+      ENV["SCHEMA_CACHE"] = "tmp/something.yml"
+
+      ActiveRecord::Tasks::DatabaseTasks.stub(:db_dir, "db") do
+        path = ActiveRecord::Tasks::DatabaseTasks.cache_dump_filename("primary")
+        assert_equal "tmp/something.yml", path
+      end
+    ensure
+      ENV["SCHEMA_CACHE"] = old_path
+    end
+
+    def test_cache_dump_filename_with_path_from_db_config
+      old_path = ENV["SCHEMA_CACHE"]
+      ENV.delete("SCHEMA_CACHE")
+
+      ActiveRecord::Tasks::DatabaseTasks.stub(:db_dir, "db") do
+        path = ActiveRecord::Tasks::DatabaseTasks.cache_dump_filename("primary", schema_cache_path: "tmp/something.yml")
+        assert_equal "tmp/something.yml", path
+      end
+    ensure
+      ENV["SCHEMA_CACHE"] = old_path
     end
   end