Basic support for ORDER BY

Author: solnic

lib/sql/composer/compiler.rb

@@ -40,6 +40,10 @@ def visit_where(node)
         add_node(Nodes::Where, operations: node)
       end
 
+      def visit_order(node)
+        add_node(Nodes::Order, operations: node)
+      end
+
       private
 
       def add_node(klass, options)

lib/sql/composer/nodes.rb

@@ -4,5 +4,7 @@
 require "sql/composer/nodes/select"
 require "sql/composer/nodes/from"
 require "sql/composer/nodes/where"
+require "sql/composer/nodes/order"
 require "sql/composer/nodes/operations/eql"
+require "sql/composer/nodes/operations/order_direction"
 require "sql/composer/nodes/value"

lib/sql/composer/nodes/identifier.rb

@@ -14,6 +14,14 @@ def to_s
           qualify? ? [qualifier, quote(name)].map(&:to_s).join(".") : quote(name)
         end
 
+        def asc
+          Operations::Asc.new(self)
+        end
+
+        def desc
+          Operations::Desc.new(self)
+        end
+
         def qualifier
           fetch(:qualifier)
         end

lib/sql/composer/nodes/operations/order_direction.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module SQL
+  module Composer
+    module Nodes
+      module Operations
+        class OrderDirection
+          attr_reader :source
+
+          def initialize(source)
+            @source = source
+          end
+
+          def to_s
+            "#{source.to_s} #{direction}"
+          end
+        end
+
+        class Asc < OrderDirection
+          def direction
+            "ASC"
+          end
+        end
+
+        class Desc < OrderDirection
+          def direction
+            "DESC"
+          end
+        end
+      end
+    end
+  end
+end

lib/sql/composer/nodes/order.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require "sql/composer/nodes/core"
+
+module SQL
+  module Composer
+    module Nodes
+      class Order < Core
+        def operations
+          fetch(:operations)
+        end
+
+        def to_s
+          "ORDER BY #{operations.map(&:to_s).join(', ')}"
+        end
+      end
+    end
+  end
+end

spec/integration/sql/compose_spec.rb

@@ -22,19 +22,43 @@ def build(&block)
     SQL.compose(backend: :postgres, args: UsersRelation.new, &block)
   end
 
-  it "works" do
-    result = build { |users|
-      select users.id, users.name
-        from users.table
-        where users.name == "Jane"
-    }
-
-    expect(result.to_s).to eql(
-      <<~SQL.strip
-      SELECT "users"."id", "users"."name"
-      FROM "users"
-      WHERE "users"."name" == 'Jane'
-      SQL
-    )
+  describe "SELECT" do
+    context "without ORDER" do
+      specify do
+        result = build { |users|
+          select users.id, users.name
+            from users.table
+            where users.name == "Jane"
+        }
+
+        expect(result.to_s).to eql(
+          <<~SQL.strip
+          SELECT "users"."id", "users"."name"
+          FROM "users"
+          WHERE "users"."name" == 'Jane'
+          SQL
+        )
+      end
+    end
+
+    context "with ORDER" do
+      specify do
+        result = build { |users|
+          select users.id, users.name
+            from users.table
+            where users.name == "Jane"
+            order users.id.desc
+        }
+
+        expect(result.to_s).to eql(
+          <<~SQL.strip
+          SELECT "users"."id", "users"."name"
+          FROM "users"
+          WHERE "users"."name" == 'Jane'
+          ORDER BY "users"."id" DESC
+          SQL
+        )
+      end
+    end
   end
 end