Bring back "database already exists" messages when running rake tasks

When running tasks such "rake db:setup", instead of showing messages
like "db_development already exists", it was showing a big stack trace
and a message "Couldn't create database for ..." with the configuration
options, a very confusing message with a big trace.

This brings back the functionality present in 3-2, showing the same
message.

4 files changed, 20 insertions, 13 deletions

diff --git a/activerecord/lib/active_record/tasks/database_tasks.rb b/activerecord/lib/active_record/tasks/database_tasks.rb
index fda51b3d76..67c7e714e6 100644
--- a/activerecord/lib/active_record/tasks/database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/database_tasks.rb
@@ -1,5 +1,7 @@
 module ActiveRecord
   module Tasks # :nodoc:
+    class DatabaseAlreadyExists < StandardError; end # :nodoc:
+
     module DatabaseTasks # :nodoc:
       extend self
 
@@ -32,6 +34,8 @@ module ActiveRecord
       def create(*arguments)
         configuration = arguments.first
         class_for_adapter(configuration['adapter']).new(*arguments).create
+      rescue DatabaseAlreadyExists
+        $stderr.puts "#{configuration['database']} already exists"
       rescue Exception => error
         $stderr.puts error, *(error.backtrace)
         $stderr.puts "Couldn't create database for #{configuration.inspect}"
diff --git a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
index 3d27c97254..3ae5aa2cea 100644
--- a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
@@ -24,10 +24,13 @@ module ActiveRecord
         connection.create_database configuration['database'], creation_options
         connection.execute grant_statement.gsub(/\s+/, ' ').strip
         establish_connection configuration
-      rescue error_class => error
-        $stderr.puts error.error
-        $stderr.puts "Couldn't create database for #{configuration.inspect}, #{creation_options.inspect}"
-        $stderr.puts "(If you set the charset manually, make sure you have a matching collation)" if configuration['encoding']
+      rescue error_class, ActiveRecord::StatementInvalid => error
+        if /database exists/ === error.message
+          raise DatabaseAlreadyExists
+        else
+          $stderr.puts "Couldn't create database for #{configuration.inspect}, #{creation_options.inspect}"
+          $stderr.puts "(If you set the charset manually, make sure you have a matching collation)" if configuration['encoding']
+        end
       end
 
       def drop
@@ -87,14 +90,11 @@ module ActiveRecord
       end
 
       def error_class
-        case configuration['adapter']
-        when /jdbc/
+        if configuration['adapter'] =~ /jdbc/
           require 'active_record/railties/jdbcmysql_error'
           ArJdbcMySQL::Error
-        when /mysql2/
-          Mysql2::Error
         else
-          Mysql::Error
+          defined?(Mysql2) ? Mysql2::Error : Mysql::Error
         end
       end
 
diff --git a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
index ea5cb888fb..e6a85b1917 100644
--- a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
@@ -18,6 +18,12 @@ module ActiveRecord
         connection.create_database configuration['database'],
           configuration.merge('encoding' => encoding)
         establish_connection configuration
+      rescue ActiveRecord::StatementInvalid => error
+        if /database .* already exists/ === error.message
+          raise DatabaseAlreadyExists
+        else
+          raise
+        end
       end
 
       def drop
diff --git a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
index da01058a82..33c43c7774 100644
--- a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
@@ -9,10 +9,7 @@ module ActiveRecord
       end
 
       def create
-        if File.exist?(configuration['database'])
-          $stderr.puts "#{configuration['database']} already exists"
-          return
-        end
+        raise DatabaseAlreadyExists if File.exist?(configuration['database'])
 
         establish_connection configuration
         connection