Allow quoted identifier string as safe SQL string

Currently `posts.title` is regarded as a safe SQL string, but
`"posts"."title"` (it is a result of `quote_table_name("posts.title")`)
is regarded as an unsafe SQL string even though a result of
`quote_table_name` should obviously be regarded as a safe SQL string,
since the column name matcher doesn't respect quotation, it is a little
annoying.

This changes the column name matcher to allow quoted identifiers as safe
SQL string, now all results of the `quote_table_name` are regarded as
safe SQL string.

4 files changed, 105 insertions, 5 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index 2877530917..99e1a11f30 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -142,6 +142,43 @@ module ActiveRecord
         value.to_s.gsub(%r{ (/ (?: | \g<1>) \*) \+? \s* | \s* (\* (?: | \g<2>) /) }x, "")
       end
 
+      def column_name_matcher # :nodoc:
+        COLUMN_NAME
+      end
+
+      def column_name_with_order_matcher # :nodoc:
+        COLUMN_NAME_WITH_ORDER
+      end
+
+      # Regexp for column names (with or without a table name prefix).
+      # Matches the following:
+      #
+      #   "#{table_name}.#{column_name}"
+      #   "#{column_name}"
+      COLUMN_NAME = /\A(?:\w+\.)?\w+\z/i
+
+      # Regexp for column names with order (with or without a table name prefix,
+      # with or without various order modifiers). Matches the following:
+      #
+      #   "#{table_name}.#{column_name}"
+      #   "#{table_name}.#{column_name} #{direction}"
+      #   "#{table_name}.#{column_name} #{direction} NULLS FIRST"
+      #   "#{table_name}.#{column_name} NULLS LAST"
+      #   "#{column_name}"
+      #   "#{column_name} #{direction}"
+      #   "#{column_name} #{direction} NULLS FIRST"
+      #   "#{column_name} NULLS LAST"
+      COLUMN_NAME_WITH_ORDER = /
+        \A
+        (?:\w+\.)?
+        \w+
+        (?:\s+ASC|\s+DESC)?
+        (?:\s+NULLS\s+(?:FIRST|LAST))?
+        \z
+      /ix
+
+      private_constant :COLUMN_NAME, :COLUMN_NAME_WITH_ORDER
+
       private
         def type_casted_binds(binds)
           if binds.first.is_a?(Array)
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb b/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb
index 75564a61d6..84354c0187 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb
@@ -32,12 +32,33 @@ module ActiveRecord
           "x'#{value.hex}'"
         end
 
-        def _type_cast(value)
-          case value
-          when Date, Time then value
-          else super
-          end
+        def column_name_matcher
+          COLUMN_NAME
+        end
+
+        def column_name_with_order_matcher
+          COLUMN_NAME_WITH_ORDER
         end
+
+        COLUMN_NAME = /\A(?:(`?)\w+\k<1>\.)?(`?)\w+\k<2>\z/i
+
+        COLUMN_NAME_WITH_ORDER = /
+          \A
+          (?:(`?)\w+\k<1>\.)?
+          (`?)\w+\k<2>
+          (?:\s+ASC|\s+DESC)?
+          \z
+        /ix
+
+        private_constant :COLUMN_NAME, :COLUMN_NAME_WITH_ORDER
+
+        private
+          def _type_cast(value)
+            case value
+            when Date, Time then value
+            else super
+            end
+          end
       end
     end
   end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
index d40e0ef1f0..0ebed21717 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
@@ -78,6 +78,28 @@ module ActiveRecord
           type_map.lookup(column.oid, column.fmod, column.sql_type)
         end
 
+        def column_name_matcher
+          COLUMN_NAME
+        end
+
+        def column_name_with_order_matcher
+          COLUMN_NAME_WITH_ORDER
+        end
+
+        COLUMN_NAME = /\A(?:("?)\w+\k<1>\.)?("?)\w+\k<2>(?:::\w+)?\z/i
+
+        COLUMN_NAME_WITH_ORDER = /
+          \A
+          (?:("?)\w+\k<1>\.)?
+          ("?)\w+\k<2>
+          (?:::\w+)?
+          (?:\s+ASC|\s+DESC)?
+          (?:\s+NULLS\s+(?:FIRST|LAST))?
+          \z
+        /ix
+
+        private_constant :COLUMN_NAME, :COLUMN_NAME_WITH_ORDER
+
         private
           def lookup_cast_type(sql_type)
             super(query_value("SELECT #{quote(sql_type)}::regtype::oid", "SCHEMA").to_i)
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
index cb9d32a577..79d477cdb2 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
@@ -45,6 +45,26 @@ module ActiveRecord
           0
         end
 
+        def column_name_matcher
+          COLUMN_NAME
+        end
+
+        def column_name_with_order_matcher
+          COLUMN_NAME_WITH_ORDER
+        end
+
+        COLUMN_NAME = /\A(?:("?)\w+\k<1>\.)?("?)\w+\k<2>\z/i
+
+        COLUMN_NAME_WITH_ORDER = /
+          \A
+          (?:("?)\w+\k<1>\.)?
+          ("?)\w+\k<2>
+          (?:\s+ASC|\s+DESC)?
+          \z
+        /ix
+
+        private_constant :COLUMN_NAME, :COLUMN_NAME_WITH_ORDER
+
         private
 
           def _type_cast(value)