Unused argument rule (#52)

* Unused argument rule

* IgnoreDefs, IgnoreBlocks, IgnoreProcs parameters

* Implicit reference by super keyworkd

* Handle macro arguments

spec/ameba/rule/unused_argument_spec.cr

@@ -0,0 +1,259 @@
+require "../../spec_helper"
+
+module Ameba::Rule
+  subject = UnusedArgument.new
+  subject.ignore_defs = false
+
+  describe UnusedArgument do
+    it "doesn't report if arguments are used" do
+      s = Source.new %(
+        def method(a, b, c)
+          a + b + c
+        end
+
+        3.times do |i|
+          i + 1
+        end
+
+        ->(i : Int32) { i + 1 }
+      )
+      subject.catch(s).should be_valid
+    end
+
+    it "reports if method argument is unused" do
+      s = Source.new %(
+        def method(a, b, c)
+          a + b
+        end
+      )
+      subject.catch(s).should_not be_valid
+      s.errors.first.message.should eq "Unused argument `c`"
+    end
+
+    it "reports if block argument is unused" do
+      s = Source.new %(
+        [1,2].each_with_index do |a, i|
+          a
+        end
+      )
+      subject.catch(s).should_not be_valid
+      s.errors.first.message.should eq "Unused argument `i`"
+    end
+
+    it "reports if proc argument is unused" do
+      s = Source.new %(
+        -> (a : Int32, b : String) do
+          a = a + 1
+        end
+      )
+      subject.catch(s).should_not be_valid
+      s.errors.first.message.should eq "Unused argument `b`"
+    end
+
+    it "reports multiple unused args" do
+      s = Source.new %(
+        def method(a, b, c)
+          nil
+        end
+      )
+      subject.catch(s).should_not be_valid
+      s.errors[0].message.should eq "Unused argument `a`"
+      s.errors[1].message.should eq "Unused argument `b`"
+      s.errors[2].message.should eq "Unused argument `c`"
+    end
+
+    it "doesn't report if it is an instance var argument" do
+      s = Source.new %(
+        class A
+          def method(@name)
+          end
+        end
+      )
+      subject.catch(s).should be_valid
+    end
+
+    it "doesn't report if a typed argument is used" do
+      s = Source.new %(
+        def method(x : Int32)
+          3.times do
+            puts x
+          end
+        end
+      )
+      subject.catch(s).should be_valid
+    end
+
+    it "doesn't report if an argument with default value is used" do
+      s = Source.new %(
+        def method(x = 1)
+          puts x
+        end
+      )
+      subject.catch(s).should be_valid
+    end
+
+    it "doesn't report if argument starts with a _" do
+      s = Source.new %(
+        def method(_x)
+        end
+      )
+      subject.catch(s).should be_valid
+    end
+
+    it "doesn't report if it is a block and used" do
+      s = Source.new %(
+        def method(&block)
+          block.call
+        end
+      )
+      subject.catch(s).should be_valid
+    end
+
+    it "reports if block arg is not used" do
+      s = Source.new %(
+        def method(&block)
+        end
+      )
+      subject.catch(s).should_not be_valid
+    end
+
+    it "reports if unused and there is yield" do
+      s = Source.new %(
+        def method(&block)
+          yield 1
+        end
+      )
+      subject.catch(s).should_not be_valid
+    end
+
+    it "doesn't report if variable is referenced implicitly" do
+      s = Source.new %(
+        class Bar < Foo
+          def method(a, b)
+            super
+          end
+        end
+      )
+      subject.catch(s).should be_valid
+    end
+
+    context "super" do
+      it "reports if variable is not referenced implicitly by super" do
+        s = Source.new %(
+          class Bar < Foo
+            def method(a, b)
+              super a
+            end
+          end
+        )
+        subject.catch(s).should_not be_valid
+        s.errors.first.message.should eq "Unused argument `b`"
+      end
+
+      it "reports rule, location and message" do
+        s = Source.new %(
+          def method(a)
+          end
+        ), "source.cr"
+        subject.catch(s).should_not be_valid
+        error = s.errors.first
+        error.rule.should_not be_nil
+        error.message.should eq "Unused argument `a`"
+        error.location.to_s.should eq "source.cr:2:22"
+      end
+    end
+
+    context "macro" do
+      it "doesn't report if it is a used macro argument" do
+        s = Source.new %(
+          macro my_macro(arg)
+            {% arg %}
+          end
+        )
+        subject.catch(s).should be_valid
+      end
+
+      it "doesn't report if it is a used macro block argument" do
+        s = Source.new %(
+          macro my_macro(&block)
+            {% block %}
+          end
+        )
+        subject.catch(s).should be_valid
+      end
+
+      it "doesn't report used macro args with equal names in record" do
+        s = Source.new %(
+          record X do
+            macro foo(a, b)
+              {{a}} + {{b}}
+            end
+
+            macro bar(a, b, c)
+              {{a}} + {{b}} + {{c}}
+            end
+          end
+        )
+        subject.catch(s).should be_valid
+      end
+    end
+
+    context "properties" do
+      describe "#ignore_defs" do
+        it "lets the rule to ignore def scopes if true" do
+          subject.ignore_defs = true
+          s = Source.new %(
+            def method(a)
+            end
+          )
+          subject.catch(s).should be_valid
+        end
+
+        it "lets the rule not to ignore def scopes if false" do
+          subject.ignore_defs = false
+          s = Source.new %(
+            def method(a)
+            end
+          )
+          subject.catch(s).should_not be_valid
+        end
+      end
+
+      context "#ignore_blocks" do
+        it "lets the rule to ignore block scopes if true" do
+          subject.ignore_blocks = true
+          s = Source.new %(
+            3.times { |i| puts "yo!" }
+          )
+          subject.catch(s).should be_valid
+        end
+
+        it "lets the rule not to ignore block scopes if false" do
+          subject.ignore_blocks = false
+          s = Source.new %(
+            3.times { |i| puts "yo!" }
+          )
+          subject.catch(s).should_not be_valid
+        end
+      end
+
+      context "#ignore_procs" do
+        it "lets the rule to ignore proc scopes if true" do
+          subject.ignore_procs = true
+          s = Source.new %(
+            ->(a : Int32) {}
+          )
+          subject.catch(s).should be_valid
+        end
+
+        it "lets the rule not to ignore proc scopes if false" do
+          subject.ignore_procs = false
+          s = Source.new %(
+            ->(a : Int32) {}
+          )
+          subject.catch(s).should_not be_valid
+        end
+      end
+    end
+  end
+end