Add Style/RedundantSelf rule

spec/ameba/rule/style/redundant_self_spec.cr

@@ -0,0 +1,280 @@
+require "../../../spec_helper"
+
+module Ameba::Rule::Style
+  describe RedundantSelf do
+    subject = RedundantSelf.new
+
+    it "does not report solitary `self` reference" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def bar
+            self
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report calls without a receiver" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def foo!
+            foo || 42
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used in the presence of a method argument with the same name" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def bar(foo)
+            foo || self.foo
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used in the presence of a block argument with the same name" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo
+            42
+          end
+
+          def bar
+            [1, 11, 111].map { |foo| self.foo + foo }
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used in the presence of a method argument with the same name inherited from the parent scope" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo
+            42
+          end
+
+          def bar(foo)
+            [1, 11, 111].map { |n| self.foo + n }
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used in the presence of a proc argument with the same name" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo
+            42
+          end
+
+          def bar
+            ->(foo : Int32) { self.foo + foo }
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used within the definition of a variable with the same name" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def foo!
+            foo = self.foo
+            foo
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used in the presence of a variable with the same name" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def foo!
+            foo = 42
+            bar = self.foo
+            bar
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used in the presence of a type declaration variable with the same name" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def foo!
+            foo : Int32 = 42
+            bar = self.foo
+            bar
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used in the presence of a type declaration variable with the same name (2)" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def foo!
+            foo : Int32?
+            bar = self.foo
+            bar
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used with a setter" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def foo=(value); end
+
+          def foo!
+            self.foo = 42
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used with an operators" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def +(value); end
+          def %(value); end
+          def <<(value); end
+
+          def foo
+            self + "foo"
+            self % "foo"
+            self << "foo"
+          end
+        end
+        CRYSTAL
+    end
+
+    it "does not report if `self` is used with a square bracket operators" do
+      expect_no_issues subject, <<-CRYSTAL
+        class Foo
+          def []?(i); end
+          def [](i); end
+          def []=(i, value); end
+
+          def foo?
+            self[0]?
+          end
+
+          def foo
+            self[0]
+          end
+
+          def foo!
+            self[0] = 42
+          end
+        end
+        CRYSTAL
+    end
+
+    it "reports if there is redundant `self` used in a method body" do
+      source = expect_issue subject, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def foo!
+            self.foo || 42
+          # ^^^^ error: Redundant `self` detected
+          end
+        end
+        CRYSTAL
+
+      expect_correction source, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def foo!
+            foo || 42
+          end
+        end
+        CRYSTAL
+    end
+
+    it "reports if there is redundant `self` used in a method arguments' default values" do
+      source = expect_issue subject, <<-CRYSTAL
+        class Foo
+          def foo
+            42
+          end
+
+          def foo!(bar = self.foo, baz = false)
+                       # ^^^^ error: Redundant `self` detected
+          end
+        end
+        CRYSTAL
+
+      expect_correction source, <<-CRYSTAL
+        class Foo
+          def foo
+            42
+          end
+
+          def foo!(bar = foo, baz = false)
+          end
+        end
+        CRYSTAL
+    end
+
+    it "reports if there is redundant `self` used in a string interpolation" do
+      source = expect_issue subject, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def foo!
+            "\#{self.foo || 42}"
+             # ^^^^ error: Redundant `self` detected
+          end
+        end
+        CRYSTAL
+
+      expect_correction source, <<-CRYSTAL
+        class Foo
+          def foo; end
+
+          def foo!
+            "\#{foo || 42}"
+          end
+        end
+        CRYSTAL
+    end
+
+    {% for keyword in %w[class module].map(&.id) %}
+      it "reports if there is redundant `self` within {{ keyword }} definition" do
+        source = expect_issue subject, <<-CRYSTAL
+          {{ keyword }} Foo
+            def self.foo; end
+
+            self.foo
+          # ^^^^ error: Redundant `self` detected
+          end
+          CRYSTAL
+
+        expect_correction source, <<-CRYSTAL
+          {{ keyword }} Foo
+            def self.foo; end
+
+            foo
+          end
+          CRYSTAL
+      end
+    {% end %}
+  end
+end