Allow to pass a connection to the dbconsole command

Since 0a4f600, it's possible to specify a 3-level database
configuration to gather connections by environment.

The `dbconsole` command will try to look for a database configuration
which points to the current environment but with such flavour, the
environment key is flushed out so let's add the ability to specify
the connection and pick `primary` by default to be consistent with
Active Record.

railties/CHANGELOG.md

@@ -1,3 +1,10 @@
+*   Allow to pass a custom connection name to the `rails dbconsole`
+    command when using a 3-level database configuration.
+
+        $ bin/rails dbconsole -c replica
+
+    *Robin Dupret*, *Jeremy Daer*
+
 *   Skip unused components when running `bin/rails app:update`.
 
     If the initial app generation skipped Action Cable, Active Record etc.,

railties/lib/rails/commands/dbconsole/dbconsole_command.rb

@@ -87,10 +87,15 @@ def start
 
     def config
       @config ||= begin
-        if configurations[environment].blank?
+        # We need to check whether the user passed the connection the
+        # first time around to show a consistent error message to people
+        # relying on 2-level database configuration.
+        if @options["connection"] && configurations[connection].blank?
+          raise ActiveRecord::AdapterNotSpecified, "'#{connection}' connection is not configured. Available configuration: #{configurations.inspect}"
+        elsif configurations[environment].blank? && configurations[connection].blank?
           raise ActiveRecord::AdapterNotSpecified, "'#{environment}' database is not configured. Available configuration: #{configurations.inspect}"
         else
-          configurations[environment]
+          configurations[environment].presence || configurations[connection]
         end
       end
     end
@@ -99,6 +104,10 @@ def environment
       Rails.respond_to?(:env) ? Rails.env : Rails::Command.environment
     end
 
+    def connection
+      @options.fetch(:connection, "primary")
+    end
+
     private
       def configurations # :doc:
         require APP_PATH
@@ -145,6 +154,9 @@ class DbconsoleCommand < Base # :nodoc:
       class_option :environment, aliases: "-e", type: :string,
         desc: "Specifies the environment to run this console under (test/development/production)."
 
+      class_option :connection, aliases: "-c", type: :string,
+        desc: "Specifies the connection to use."
+
       def perform
         extract_environment_option_from_argument
 

railties/test/commands/dbconsole_test.rb

@@ -200,6 +200,49 @@ def test_unknown_command_line_client
     assert_match(/Unknown command-line client for db/, output)
   end
 
+  def test_primary_is_automatically_picked_with_3_level_configuration
+    sample_config = {
+      "test" => {
+        "primary" => {
+          "adapter" => "postgresql"
+        }
+      }
+    }
+
+    app_db_config(sample_config) do
+      assert_equal "postgresql", Rails::DBConsole.new.config["adapter"]
+    end
+  end
+
+  def test_specifying_a_custom_connection_and_environment
+    stub_available_environments(["development"]) do
+      dbconsole = parse_arguments(["-c", "custom", "-e", "development"])
+
+      assert_equal "development", dbconsole[:environment]
+      assert_equal "custom", dbconsole.connection
+    end
+  end
+
+  def test_specifying_a_missing_connection
+    app_db_config({}) do
+      e = assert_raises(ActiveRecord::AdapterNotSpecified) do
+        Rails::Command.invoke(:dbconsole, ["-c", "i_do_not_exist"])
+      end
+
+      assert_includes e.message, "'i_do_not_exist' connection is not configured."
+    end
+  end
+
+  def test_specifying_a_missing_environment
+    app_db_config({}) do
+      e = assert_raises(ActiveRecord::AdapterNotSpecified) do
+        Rails::Command.invoke(:dbconsole)
+      end
+
+      assert_includes e.message, "'test' database is not configured."
+    end
+  end
+
   def test_print_help_short
     stdout = capture(:stdout) do
       Rails::Command.invoke(:dbconsole, ["-h"])