Add guards and extend trees functionality

Author: tomeroth

examples/user_pipeline.rb

@@ -64,7 +64,6 @@ def some_other_filters
     order: { 'courses.id': 'asc' },
     params: {
       limit: 10,
-      offset: 0,
       not_supported: 'omitted'
     }
   }

lib/filterly/tree.rb

@@ -27,12 +27,16 @@ def self.initialize_with_filters
     end
 
     def extend_ast(node_attr_name, new_node, stmt_type)
+      self.class.ensure_not_nil_node!(new_node)
+
       @root_node = TreeTraverser
         .new(@root_node)
         .extend_ast(node_attr_name, new_node, stmt_type)
     end
 
     def prepend_ast(new_node, stmt_type)
+      self.class.ensure_not_nil_node!(new_node)
+
       @root_node = TreeTraverser.new(@root_node).prepend_ast(new_node, stmt_type)
     end
 
@@ -44,7 +48,12 @@ def to_s
       root_node.to_s
     end
 
-    # @apir private
+    # @api private
+    def self.ensure_not_nil_node!(ast_node)
+      raise 'Tried to append nil node which is forbidden!' if ast_node.nil?
+    end
+
+    # @api private
     def self.ensure_ast_root!(root_node)
       raise 'Not a tree root!' if root_node.type != :root
     end
@@ -95,6 +104,8 @@ def recreate_node(node_attr_name, new_node, stmt_type)
       end
 
       def prepend_ast(new_node, stmt_type)
+        return prepend_ast_without_statement(new_node) if ast_node.leaf?
+
         create_node(
           ast_node.type,
           [
@@ -108,6 +119,18 @@ def prepend_ast(new_node, stmt_type)
         )
       end
 
+      # @api private
+      def prepend_ast_without_statement(new_node)
+        create_node(
+          ast_node.type,
+          [
+            ast_node.value,
+            new_node,
+            nil
+          ]
+        )
+      end
+
       # @api private
       def create_node(*args)
         Filterly::Node.new(*args)

spec/unit/pipeline/param_builder_spec.rb

@@ -73,35 +73,28 @@
                   [
                     :and,
                     [
-                      :statement,
+                      :expression,
                       [
-                        :and,
+                        :op_in,
+                        [:attr_name, [:category_ids, [], []]],
                         [
-                          :expression,
+                          :attr_array,
                           [
-                            :op_in,
-                            [:attr_name, [:category_ids, [], []]],
-                            [
-                              :attr_array,
-                              [
-                                12,
-                                [:attr_array, [34, [], []]],
-                                [:attr_array, [54, [], []]]
-                              ]
-                            ]
-                          ]
-                        ],
-                        [
-                          :expression,
-                          [
-                            :op_equal,
-                            [:attr_name, [:course_semester_id, [], []]],
-                            [:attr_value, [123, [], []]]
+                            12,
+                            [:attr_array, [34, [], []]],
+                            [:attr_array, [54, [], []]]
                           ]
                         ]
                       ]
                     ],
-                    []
+                    [
+                      :expression,
+                      [
+                        :op_equal,
+                        [:attr_name, [:course_semester_id, [], []]],
+                        [:attr_value, [123, [], []]]
+                      ]
+                    ]
                   ]
                 ]
               ]

spec/unit/tree_spec.rb

@@ -99,6 +99,14 @@
   end
 
   describe '#extend_ast' do
+    it 'tries to extend with nil node and fails' do
+      tree = described_class.initialize_with_filters
+
+      expect { tree.extend_ast('name', nil, :or) }.to raise_error(
+        'Tried to append nil node which is forbidden!'
+      )
+    end
+
     it 'adds a new node to specific node and returns root' do
       subject.extend_ast(node_attr_name, new_node, :or)
 
@@ -226,5 +234,36 @@
         ]
       )
     end
+
+    it 'adds a new node without statement for empty tree' do
+      tree = described_class.initialize_with_filters
+      tree.prepend_ast(new_node, :or)
+
+      expect(tree.to_ast.to_a).to match_array(
+        [
+          :root,
+          [
+            :filters,
+            [
+              :expression,
+              [
+                :op_equal,
+                [:attr_name, [:whatever_id, [], []]],
+                [:attr_value, [13, [], []]]
+              ]
+            ],
+            []
+          ]
+        ]
+      )
+    end
+
+    it 'tries to add nil node and fails' do
+      tree = described_class.initialize_with_filters
+
+      expect { tree.prepend_ast(nil, :or) }.to raise_error(
+        'Tried to append nil node which is forbidden!'
+      )
+    end
   end
 end