Clarify 'database does not exist' message and implementation.

* Clarify what the situation is and what to do.
* Advise loading schema using `rake db:setup` instead of migrating.
* Use a rescue in the initializer rather than extending the error
  message in-place.
* Preserve the original backtrace of other errors by using `raise`
  rather than raising again with `raise error`.

References 0ec45cd15d

activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb

@@ -20,9 +20,9 @@ module ActiveRecord
       ConnectionAdapters::Mysql2Adapter.new(client, logger, options, config)
     rescue Mysql2::Error => error
       if error.message.include?("Unknown database")
-        raise ActiveRecord::NoDatabaseError.new(error.message)
+        raise ActiveRecord::NoDatabaseError.new(error.message, error)
       else
-        raise error
+        raise
       end
     end
   end

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -36,9 +36,9 @@ module ActiveRecord
       ConnectionAdapters::MysqlAdapter.new(mysql, logger, options, config)
     rescue Mysql::Error => error
       if error.message.include?("Unknown database")
-        raise ActiveRecord::NoDatabaseError.new(error.message)
+        raise ActiveRecord::NoDatabaseError.new(error.message, error)
       else
-        raise error
+        raise
       end
     end
   end

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -718,9 +718,9 @@ module ActiveRecord
           configure_connection
         rescue ::PG::Error => error
           if error.message.include?("does not exist")
-            raise ActiveRecord::NoDatabaseError.new(error.message)
+            raise ActiveRecord::NoDatabaseError.new(error.message, error)
           else
-            raise error
+            raise
           end
         end
 

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -33,9 +33,9 @@ module ActiveRecord
       ConnectionAdapters::SQLite3Adapter.new(db, logger, config)
     rescue Errno::ENOENT => error
       if error.message.include?("No such file or directory")
-        raise ActiveRecord::NoDatabaseError.new(error.message)
+        raise ActiveRecord::NoDatabaseError.new(error.message, error)
       else
-        raise error
+        raise
       end
     end
   end

activerecord/lib/active_record/errors.rb

@@ -95,15 +95,7 @@ module ActiveRecord
   end
 
   # Raised when a given database does not exist
-  class NoDatabaseError < ActiveRecordError
-    def initialize(message)
-      super extend_message(message)
-    end
-
-    # can be over written to add additional error information.
-    def extend_message(message)
-      message
-    end
+  class NoDatabaseError < StatementInvalid
   end
 
   # Raised on attempt to save stale record. Record is stale when it's being saved in another query after

activerecord/lib/active_record/railtie.rb

@@ -116,17 +116,22 @@ module ActiveRecord
     # and then establishes the connection.
     initializer "active_record.initialize_database" do |app|
       ActiveSupport.on_load(:active_record) do
-
-        class ActiveRecord::NoDatabaseError
-          remove_possible_method :extend_message
-          def extend_message(message)
-            message << "Run `$ bin/rake db:create db:migrate` to create your database"
-            message
-          end
-        end
-
         self.configurations = Rails.application.config.database_configuration
-        establish_connection
+
+        begin
+          establish_connection
+        rescue ActiveRecord::NoDatabaseError
+          warn <<-end_warning
+Oops - You have a database configured, but it doesn't exist yet!
+
+Here's how to get started:
+
+  1. Configure your database in config/database.yml.
+  2. Run `bin/rake db:create` to create the database.
+  3. Run `bin/rake db:setup` to load your database schema.
+end_warning
+          raise
+        end
       end
     end