Accept any Enumerable input and remove Param.coerce

Both Multipart and Urlencoded encoders now consistently accept any
Enumerable of key-value pairs (Hash, Array, Enumerator, etc.) instead
of requiring Hash or Array specifically. This is done via a new
FormData.ensure_data method that coerces input to an Enumerable.

* Remove Param.coerce and inline its logic into Multipart#parts
* Replace FormData.ensure_hash with FormData.ensure_data in encoders
* Add tests for Enumerable input on both Multipart and ensure_data

Author: sferik

lib/http/form_data.rb

@@ -38,11 +38,11 @@ class << self
       # FormData factory. Automatically selects best type depending on given
       # `data` Hash.
       #
-      # @param [#to_h, Hash] data
+      # @param [Enumerable, Hash, #to_h] data
       # @return [Multipart] if any of values is a {FormData::File}
       # @return [Urlencoded] otherwise
       def create(data, encoder: nil)
-        data = ensure_hash data
+        data = ensure_data data
 
         if multipart?(data)
           Multipart.new(data)
@@ -64,6 +64,18 @@ def ensure_hash(obj)
         end
       end
 
+      # Coerce `obj` to an Enumerable of key-value pairs.
+      #
+      # @raise [Error] `obj` can't be coerced.
+      # @return [Enumerable]
+      def ensure_data(obj)
+        if    obj.nil?                  then []
+        elsif obj.is_a?(Enumerable)     then obj
+        elsif obj.respond_to?(:to_h)    then obj.to_h
+        else raise Error, "#{obj.inspect} is neither Enumerable nor responds to :to_h"
+        end
+      end
+
       private
 
       # Tells whenever data contains multipart data or not.

lib/http/form_data/multipart.rb

@@ -14,7 +14,7 @@ class Multipart
 
       attr_reader :boundary
 
-      # @param [#to_h, Hash] data form data key-value Hash
+      # @param [Enumerable, Hash, #to_h] data form data key-value pairs
       def initialize(data, boundary: self.class.generate_boundary)
         @boundary = boundary.to_s.freeze
         @io = CompositeIO.new(parts(data).flat_map { |part| [glue, part] } << tail)
@@ -54,11 +54,15 @@ def tail
       end
 
       def parts(data)
-        if data.is_a?(Array)
-          Param.coerce data
-        else
-          Param.coerce FormData.ensure_hash data
+        params = []
+
+        FormData.ensure_data(data).each do |name, values|
+          Array(values).each do |value|
+            params << Param.new(name, value)
+          end
         end
+
+        params
       end
     end
   end

lib/http/form_data/multipart/param.rb

@@ -41,24 +41,6 @@ def initialize(name, value)
           @io = CompositeIO.new [header, @part, footer]
         end
 
-        # Flattens given `data` Hash or Array into an array of `Param`'s.
-        # Nested arrays are unwinded.
-        # Behavior is similar to `URL.encode_www_form`.
-        #
-        # @param [Array || Hash] data
-        # @return [Array<FormData::MultiPart::Param>]
-        def self.coerce(data)
-          params = []
-
-          data.each do |name, values|
-            Array(values).each do |value|
-              params << new(name, value)
-            end
-          end
-
-          params
-        end
-
         private
 
         def header

lib/http/form_data/urlencoded.rb

@@ -95,10 +95,10 @@ def escape(value)
         private_constant :DefaultEncoder
       end
 
-      # @param [#to_h, Hash] data form data key-value Hash
+      # @param [Enumerable, Hash, #to_h] data form data key-value pairs
       def initialize(data, encoder: nil)
         encoder ||= self.class.encoder
-        @io = StringIO.new(encoder.call(FormData.ensure_hash(data)))
+        @io = StringIO.new(encoder.call(FormData.ensure_data(data)))
       end
 
       # Returns MIME type to be used for HTTP request `Content-Type` header.

spec/lib/http/form_data/multipart_spec.rb

@@ -87,6 +87,22 @@ def disposition(params)
       end
     end
 
+    it "supports any Enumerable of pairs" do
+      enum = Enumerator.new { |y| y << [:foo, :bar] << [:foo, :baz] }
+      form_data = described_class.new(enum)
+
+      boundary_value = form_data.boundary
+      expect(form_data.to_s).to eq([
+        "--#{boundary_value}#{crlf}",
+        "#{disposition 'name' => 'foo'}#{crlf}",
+        "#{crlf}bar#{crlf}",
+        "--#{boundary_value}#{crlf}",
+        "#{disposition 'name' => 'foo'}#{crlf}",
+        "#{crlf}baz#{crlf}",
+        "--#{boundary_value}--#{crlf}"
+      ].join)
+    end
+
     # https://github.com/httprb/http/issues/663
     context "when params is an Array of pairs" do
       let(:params) do

spec/lib/http/form_data_spec.rb

@@ -22,6 +22,42 @@
     end
   end
 
+  describe ".ensure_data" do
+    subject(:ensure_data) { HTTP::FormData.ensure_data data }
+
+    context "when Hash given" do
+      let(:data) { { :foo => :bar } }
+      it { is_expected.to eq :foo => :bar }
+    end
+
+    context "when Array given" do
+      let(:data) { [[:foo, :bar], [:foo, :baz]] }
+      it { is_expected.to eq [[:foo, :bar], [:foo, :baz]] }
+    end
+
+    context "when Enumerator given" do
+      let(:data) { Enumerator.new { |y| y << [:foo, :bar] } }
+      it { is_expected.to be_a Enumerator }
+    end
+
+    context "when #to_h given" do
+      let(:data) { double(:to_h => { :foo => :bar }) }
+      it { is_expected.to eq :foo => :bar }
+    end
+
+    context "when nil given" do
+      let(:data) { nil }
+      it { is_expected.to eq([]) }
+    end
+
+    context "when neither Enumerable nor #to_h given" do
+      let(:data) { double }
+      it "fails with HTTP::FormData::Error" do
+        expect { ensure_data }.to raise_error HTTP::FormData::Error
+      end
+    end
+  end
+
   describe ".ensure_hash" do
     subject(:ensure_hash) { HTTP::FormData.ensure_hash data }