raise `ArgumentError` when redefining the primary key column. Closes #6378

activerecord/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   The `create_table` method raises an `ArgumentError` when the primary key column is redefined.
+    Fix #6378
+
+    *Yves Senn*
+
 *   `ActiveRecord::AttributeMethods#[]` raises `ActiveModel::MissingAttributeError`
     error if the given attribute is missing. Fixes #5433.
 

activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb

@@ -234,6 +234,10 @@ def column(name, type, options = {})
         name = name.to_s
         type = type.to_sym
 
+        if primary_key_column_name == name
+          raise ArgumentError, "you can't redefine the primary key column '#{name}'. To define a custom primary key, pass { id: false } to create_table."
+        end
+
         column = self[name] || new_column_definition(@base, name, type)
 
         limit = options.fetch(:limit) do
@@ -302,6 +306,11 @@ def new_column_definition(base, name, type)
         definition
       end
 
+      def primary_key_column_name
+        primary_key_column = columns.detect { |c| c.type == :primary_key }
+        primary_key_column && primary_key_column.name
+      end
+
       def native
         @base.native_database_types
       end

activerecord/test/cases/migration/change_schema_test.rb

@@ -132,6 +132,26 @@ def test_create_table_with_primary_key_prefix_as_table_name
         assert_equal %w(foo testingid), connection.columns(:testings).map(&:name).sort
       end
 
+      def test_create_table_raises_when_redefining_primary_key_column
+        error = assert_raise(ArgumentError) do
+          connection.create_table :testings do |t|
+            t.column :id, :string
+          end
+        end
+
+        assert_equal "you can't redefine the primary key column 'id'. To define a custom primary key, pass { id: false } to create_table.", error.message
+      end
+
+      def test_create_table_raises_when_redefining_custom_primary_key_column
+        error = assert_raise(ArgumentError) do
+          connection.create_table :testings, primary_key: :testing_id do |t|
+            t.column :testing_id, :string
+          end
+        end
+
+        assert_equal "you can't redefine the primary key column 'testing_id'. To define a custom primary key, pass { id: false } to create_table.", error.message
+      end
+
       def test_create_table_with_timestamps_should_create_datetime_columns
         connection.create_table table_name do |t|
           t.timestamps