Add struct_constructor?, class_definition? and module_definition? mat…

…chers

Closes rubocop#28

CHANGELOG.md

@@ -7,6 +7,7 @@
 * [#4](https://github.com/rubocop-hq/rubocop-ast/issues/4): Add `interpolation?` for `RegexpNode`. ([@tejasbubane][])
 * [#20](https://github.com/rubocop-hq/rubocop-ast/pull/20): Add option predicates for `RegexpNode`. ([@owst][])
 * [#11](https://github.com/rubocop-hq/rubocop-ast/issues/11): Add `argument_type?` method to make it easy to recognize argument nodes. ([@tejasbubane][])
+* [#28](https://github.com/rubocop-hq/rubocop-ast/issues/28): Add `struct_constructor?`, `class_definition?` and `module_definition?` matchers. ([@tejasbubane][])
 
 ## 0.0.3 (2020-05-15)
 

lib/rubocop/ast/node.rb

@@ -497,6 +497,20 @@ def guard_clause?
          (block (send (const nil? {:Class :Module}) :new ...) ...)}
       PATTERN
 
+      def_node_matcher :struct_constructor?, <<~PATTERN
+        (block (send (const nil? :Struct) :new ...) ...)
+      PATTERN
+
+      def_node_matcher :class_definition?, <<~PATTERN
+        {(class (const nil? _) {nil? (const nil? _)} ...)
+         (casgn nil? _ (block (send (const nil? {:Struct :Class}) :new ...) ...))}
+      PATTERN
+
+      def_node_matcher :module_definition?, <<~PATTERN
+        {(module (const nil? _) ...)
+         (casgn nil? _ (block (send (const nil? :Module) :new ...) ...))}
+      PATTERN
+
       # Some expressions are evaluated for their value, some for their side
       # effects, and some for both
       # If we know that an expression is useful only for its side effects, that

spec/rubocop/ast/node_spec.rb

@@ -373,4 +373,146 @@ def used?
       end
     end
   end
+
+  describe '#class_constructor?' do
+    context 'class definition with a block' do
+      let(:src) { 'Class.new { a = 42 }' }
+
+      it 'matches' do
+        expect(node.class_constructor?).to eq(true)
+      end
+    end
+
+    context 'module definition with a block' do
+      let(:src) { 'Module.new { a = 42 }' }
+
+      it 'matches' do
+        expect(node.class_constructor?).to eq(true)
+      end
+    end
+
+    context 'class definition' do
+      let(:src) { 'class Foo; a = 42; end' }
+
+      it 'does not match' do
+        expect(node.class_constructor?).to eq(nil)
+      end
+    end
+  end
+
+  describe '#struct_constructor?' do
+    context 'struct definition with a block' do
+      let(:src) { 'Struct.new { a = 42 }' }
+
+      it 'matches' do
+        expect(node.struct_constructor?).to eq(true)
+      end
+    end
+
+    context 'struct definition without block' do
+      let(:src) { 'Struct.new(:foo, :bar)' }
+
+      it 'does not matches' do
+        expect(node.struct_constructor?).to eq(nil)
+      end
+    end
+  end
+
+  describe '#class_definition?' do
+    context 'without inheritance' do
+      let(:src) { 'class Foo; a = 42; end' }
+
+      it 'matches' do
+        expect(node.class_definition?).to eq(true)
+      end
+    end
+
+    context 'with inheritance' do
+      let(:src) { 'class Foo < Bar; a = 42; end' }
+
+      it 'matches' do
+        expect(node.class_definition?).to eq(true)
+      end
+    end
+
+    context 'with Struct' do
+      let(:src) do
+        <<~RUBY
+          Person = Struct.new(:name, :age) do
+            a = 2
+            def details; end
+          end
+        RUBY
+      end
+
+      it 'matches' do
+        expect(node.class_definition?).to eq(true)
+      end
+    end
+
+    context 'constant defined as Struct without block' do
+      let(:src) { 'Person = Struct.new(:name, :age)' }
+
+      it 'does not match' do
+        expect(node.class_definition?).to eq(nil)
+      end
+    end
+
+    context 'with Class.new' do
+      let(:src) do
+        <<~RUBY
+          Person = Class.new(:name, :age) do
+            a = 2
+            def details; end
+          end
+        RUBY
+      end
+
+      it 'matches' do
+        expect(node.class_definition?).to eq(true)
+      end
+    end
+  end
+
+  describe '#module_definition?' do
+    context 'using module keyword' do
+      let(:src) { 'module Foo; A = 42; end' }
+
+      it 'matches' do
+        expect(node.module_definition?).to eq(true)
+      end
+    end
+
+    context 'with Module.new' do
+      let(:src) do
+        <<~RUBY
+          Person = Module.new(:name, :age) do
+            a = 2
+            def details; end
+          end
+        RUBY
+      end
+
+      it 'matches' do
+        expect(node.module_definition?).to eq(true)
+      end
+    end
+
+    context 'nested modules' do
+      let(:src) do
+        <<~RUBY
+          module Foo
+            module Bar
+              BAZ = 2
+              def variables; end
+            end
+          end
+        RUBY
+      end
+
+      it 'matches' do
+        expect(node.module_definition?).to eq(true)
+      end
+    end
+  end
 end