Merge pull request #34 from davidrunger/add-method-shape

Add a `Method` shape

CHANGELOG.md

@@ -1,6 +1,10 @@
 ## Unreleased
 ### BREAKING CHANGES
 - Rename the `Or` shape to `Any`
+- Add a `Method` shape (where the shape description is the name of a method which, when called on a
+  test object, must return a truthy value). This is a breaking change because the `Shaped::Shape`
+  constructor will now return an instance of `Shaped::Shapes::Method` rather than
+  `Shaped::Shapes::Equality` when called with a Symbol argument.
 
 ### Added
 - Add an `All` shape (w/ multiple sub-shapes, all of which must be matched)

README.md

@@ -21,6 +21,7 @@ Validate the "shape" of Ruby objects!
       * [Shaped::Shapes::Array](#shapedshapesarray)
       * [Shaped::Shapes::Class](#shapedshapesclass)
          * [ActiveModel validations](#activemodel-validations)
+      * [Shaped::Shapes::Method](#shapedshapesmethod)
       * [Shaped::Shapes::Callable](#shapedshapescallable)
       * [Shaped::Shapes::Equality](#shapedshapesequality)
       * [Shaped::Shapes::Any](#shapedshapesany)
@@ -30,7 +31,7 @@ Validate the "shape" of Ruby objects!
    * [For maintainers](#for-maintainers)
    * [License](#license)
 
-<!-- Added by: david, at: Wed Jun 24 13:23:10 PDT 2020 -->
+<!-- Added by: david, at: Wed Jun 24 13:56:49 PDT 2020 -->
 
 <!--te-->
 
@@ -205,6 +206,21 @@ shape.matched_by?('[email protected]') # too short
 # => false
 ```
 
+## Shaped::Shapes::Method
+
+This shape allows specifying a method name that, when called upon a test object, must return a
+truthy value in order for `matched_by?` to be true.
+
+```rb
+shape = Shaped::Shape(:odd?)
+
+shape.matched_by?(55)
+# => true
+
+shape.matched_by?(60)
+# => false
+```
+
 ## Shaped::Shapes::Callable
 
 This shape is very powerful if you need a very customized shape definition; you can define any

lib/shaped.rb

@@ -30,6 +30,7 @@ def self.Shape(*shape_descriptions)
       when Shaped::Shape then shape_description
       when Hash then Shaped::Shapes::Hash.new(shape_description)
       when Array then Shaped::Shapes::Array.new(shape_description)
+      when Symbol then Shaped::Shapes::Method.new(shape_description)
       when Class then Shaped::Shapes::Class.new(shape_description, validation_options)
       else
         if shape_description.respond_to?(:call)

lib/shaped/shapes/method.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class Shaped::Shapes::Method < Shaped::Shape
+  def initialize(method_name)
+    @method_name = method_name
+  end
+
+  def matched_by?(object)
+    !!object.public_send(@method_name)
+  end
+
+  def to_s
+    "object returning truthy for ##{@method_name}"
+  end
+end

spec/shaped_spec.rb

@@ -33,6 +33,14 @@
         end
       end
 
+      context 'when called with a Symbol' do
+        let(:shape_description) { :valid? }
+
+        it 'returns an instance of Shaped::Shapes::Method' do
+          expect(shape).to be_a(Shaped::Shapes::Method)
+        end
+      end
+
       context 'when called with a Class' do
         let(:shape_description) { Numeric }
 

spec/shapes/all_spec.rb

@@ -3,7 +3,7 @@
 RSpec.describe Shaped::Shapes::All do
   subject(:all_shape) { Shaped::Shapes::All.new(*all_shape_descriptions) }
 
-  let(:all_shape_descriptions) { [Numeric, ->(number) { number.even? }] }
+  let(:all_shape_descriptions) { [Numeric, :even?] }
   let(:test_object) { 88 }
 
   describe '#initialize' do
@@ -32,7 +32,7 @@
     context 'when the test object satisfies all of the sub-shape descriptions' do
       before do
         expect(test_object).to be_a(all_shape_descriptions.first)
-        expect(all_shape_descriptions.second.call(test_object)).to eq(true)
+        expect(test_object.public_send(all_shape_descriptions.second)).to eq(true)
       end
 
       it 'returns true' do
@@ -45,7 +45,7 @@
 
       before do
         expect(test_object).to be_a(all_shape_descriptions.first) # matched
-        expect(all_shape_descriptions.second.call(test_object)).to eq(false) # not matched
+        expect(test_object.public_send(all_shape_descriptions.second)).to eq(false) # not matched
       end
 
       it 'returns false' do
@@ -57,8 +57,8 @@
   describe '#to_s' do
     subject(:to_s) { all_shape.to_s }
 
-    it 'returns a readably formatted description of the list of allowed shapes' do
-      expect(to_s).to match(/Numeric AND Proc test defined at .*all_spec\.rb:\d+/)
+    it 'returns a readably formatted description of the list of required shapes' do
+      expect(to_s).to eq('Numeric AND object returning truthy for #even?')
     end
   end
 end

spec/shapes/method_spec.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+RSpec.describe Shaped::Shapes::Method do
+  subject(:method_shape) { Shaped::Shapes::Method.new(method_shape_description) }
+
+  let(:method_shape_description) { :even? }
+  let(:test_object) { 64 }
+
+  describe '#initialize' do
+    it 'does not raise an error' do
+      expect { method_shape }.not_to raise_error
+    end
+  end
+
+  describe '#matched_by?' do
+    subject(:matched_by?) { method_shape.matched_by?(test_object) }
+
+    context 'when the test object returns a truthy value when called with the specified method' do
+      before { expect(test_object).to be_even }
+
+      it 'returns true' do
+        expect(matched_by?).to eq(true)
+      end
+    end
+
+    context 'when the test object returns a falsy value when called with the specified method' do
+      before { expect(test_object).not_to be_even }
+
+      let(:test_object) { 71 }
+
+      it 'returns false' do
+        expect(matched_by?).to eq(false)
+      end
+    end
+  end
+
+  describe '#to_s' do
+    subject(:to_s) { method_shape.to_s }
+
+    it 'returns a string naming the method that must be matched' do
+      expect(to_s).to eq('object returning truthy for #even?')
+    end
+  end
+end