Translate adapter errors that indicate a violated uniqueness constraint to ActiveRecord::RecordNotUnique exception derived from ActiveReecord::StatementInvalid.

Signed-off-by: Michael Koziarski <michael@koziarski.com>

activerecord/lib/active_record/base.rb

@@ -67,6 +67,10 @@ module ActiveRecord #:nodoc:
   class StatementInvalid < ActiveRecordError
   end
 
+  # Raised when a record cannot be inserted because it would violate a uniqueness constraint.
+  class RecordNotUnique < StatementInvalid
+  end
+
   # Raised when number of bind variables in statement given to <tt>:condition</tt> key (for example, when using +find+ method)
   # does not match number of expected variables.
   #

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -211,9 +211,14 @@ module ActiveRecord
           @last_verification = 0
           message = "#{e.class.name}: #{e.message}: #{sql}"
           log_info(message, name, 0)
-          raise ActiveRecord::StatementInvalid, message
+          raise translate_exception(e, message)
         end
 
+      def translate_exception(e, message)
+        # override in derived class
+        ActiveRecord::StatementInvalid.new(message)
+      end
+
         def format_log_entry(message, dump = nil)
           if ActiveRecord::Base.colorize_logging
             if @@row_even

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -563,6 +563,17 @@ module ActiveRecord
         where_sql
       end
 
+      protected
+
+        def translate_exception(exception, message)
+          case exception.errno
+          when 1062
+            RecordNotUnique.new(message)
+          else
+            super
+          end
+        end
+
       private
         def connect
           encoding = @config[:encoding]

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -941,6 +941,15 @@ module ActiveRecord
             end
         end
 
+        def translate_exception(exception, message)
+          case exception.message
+          when /duplicate key value violates unique constraint/
+            RecordNotUnique.new(message)
+          else
+            super
+          end
+        end
+
       private
         # The internal PostgreSQL identifier of the money data type.
         MONEY_COLUMN_TYPE_OID = 790 #:nodoc:

activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb

@@ -431,6 +431,16 @@ module ActiveRecord
             'INTEGER PRIMARY KEY NOT NULL'.freeze
           end
         end
+
+        def translate_exception(exception, message)
+          case exception.message
+          when /column(s)? .* (is|are) not unique/
+            RecordNotUnique.new(message)
+          else
+            super
+          end
+        end
+
     end
 
     class SQLite2Adapter < SQLiteAdapter # :nodoc:

activerecord/test/cases/adapter_test.rb

@@ -130,4 +130,11 @@ class AdapterTest < ActiveRecord::TestCase
       assert_equal " LIMIT 1,7 OFFSET 7", @connection.add_limit_offset!("", :limit=>sql_inject, :offset=>7)
     end
   end
+
+  def test_uniqueness_violations_are_translated_to_specific_exception
+    @connection.execute "INSERT INTO subscribers(nick) VALUES('me')"
+    assert_raises(ActiveRecord::RecordNotUnique) do
+      @connection.execute "INSERT INTO subscribers(nick) VALUES('me')"
+    end
+  end
 end