Merge pull request #2245 from herwinw/data_to_h

Support block argument in Data#to_h

spec/core/data/to_h_spec.rb

@@ -0,0 +1,65 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+ruby_version_is "3.2" do
+  describe "Data#to_h" do
+    it "transforms the data object into a hash" do
+      data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+      data.to_h.should == { amount: 42, unit: 'km' }
+    end
+
+    context "with block" do
+      it "transforms [key, value] pairs returned by the block into a hash" do
+        data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+        data.to_h { |key, value| [value, key] }.should == { 42 => :amount, 'km' => :unit }
+      end
+
+      it "passes to a block each pair's key and value as separate arguments" do
+        ScratchPad.record []
+        data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+        data.to_h { |k, v| ScratchPad << [k, v]; [k, v] }
+        ScratchPad.recorded.sort.should == [[:amount, 42], [:unit, 'km']]
+
+        ScratchPad.record []
+        data.to_h { |*args| ScratchPad << args; [args[0], args[1]] }
+        ScratchPad.recorded.sort.should == [[:amount, 42], [:unit, 'km']]
+      end
+
+      it "raises ArgumentError if block returns longer or shorter array" do
+        data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+        -> do
+          data.to_h { |k, v| [k.to_s, v*v, 1] }
+        end.should raise_error(ArgumentError, /element has wrong array length/)
+
+        -> do
+          data.to_h { |k, v| [k] }
+        end.should raise_error(ArgumentError, /element has wrong array length/)
+      end
+
+      it "raises TypeError if block returns something other than Array" do
+        data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+        -> do
+          data.to_h { |k, v| "not-array" }
+        end.should raise_error(TypeError, /wrong element type String/)
+      end
+
+      it "coerces returned pair to Array with #to_ary" do
+        x = mock('x')
+        x.stub!(:to_ary).and_return([:b, 'b'])
+        data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+
+        data.to_h { |k| x }.should == { :b => 'b' }
+      end
+
+      it "does not coerce returned pair to Array with #to_a" do
+        x = mock('x')
+        x.stub!(:to_a).and_return([:b, 'b'])
+        data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+
+        -> do
+          data.to_h { |k| x }
+        end.should raise_error(TypeError, /wrong element type MockObject/)
+      end
+    end
+  end
+end

src/data.rb

@@ -39,7 +39,13 @@ def self.define(*members, &block)
       end
       alias_method :to_s, :inspect
 
-      define_method(:to_h) { members.to_h { |member| [member, public_send(member)] } }
+      define_method(:to_h) do |&block|
+        if block
+          members.to_h { |member| block.call(member, public_send(member)) }
+        else
+          members.to_h { |member| [member, public_send(member)] }
+        end
+      end
 
       define_method(:with) do |**kwargs|
         if kwargs.empty?

test/natalie/data_test.rb

@@ -3,10 +3,6 @@
 
 ruby_version_is ''...'3.2' do
   describe 'we need the same number of tests here to make the ruby comparison pass' do
-    it 'transforms the data object into a hash' do
-      1.should == 1
-    end
-
     it 'results in a readable representation' do
       1.should == 1
     end
@@ -18,13 +14,6 @@
 end
 
 ruby_version_is '3.2' do
-  describe 'Data#to_h' do
-    it 'transforms the data object into a hash' do
-      data = DataSpecs::Measure.new(amount: 42, unit: 'km')
-      data.to_h.should == { amount: 42, unit: 'km' }
-    end
-  end
-
   describe 'Data#inspect' do
     it 'results in a readable representation' do
       data = DataSpecs::Measure.new(amount: 42, unit: 'km')