Introduces flat_encode option for multipart adapter.

Fixes #1157

lib/faraday/request/multipart.rb

@@ -12,6 +12,11 @@ class Multipart < UrlEncoded
         DEFAULT_BOUNDARY_PREFIX = '-----------RubyMultipartPost'
       end
 
+      def initialize(app = nil, options = {})
+        @app = app
+        @options = options
+      end
+
       # Checks for files in the payload, otherwise leaves everything untouched.
       #
       # @param env [Faraday::Env]
@@ -29,7 +34,7 @@ def call(env)
       def process_request?(env)
         type = request_type(env)
         env.body.respond_to?(:each_key) && !env.body.empty? && (
-          (type.empty? && has_multipart?(env.body)) ||
+        (type.empty? && has_multipart?(env.body)) ||
           (type == self.class.mime_type)
         )
       end
@@ -79,7 +84,11 @@ def unique_boundary
       # @param pieces [Array]
       def process_params(params, prefix = nil, pieces = nil, &block)
         params.inject(pieces || []) do |all, (key, value)|
-          key = "#{prefix}[#{key}]" if prefix
+          if @options[:flat_encode]
+            key = prefix.to_s if prefix
+          else
+            key = "#{prefix}[#{key}]" if prefix
+          end
 
           case value
           when Array

spec/faraday/request/multipart_spec.rb

@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 
 RSpec.describe Faraday::Request::Multipart do
+  let(:options) { {} }
   let(:conn) do
     Faraday.new do |b|
-      b.request :multipart
+      b.request :multipart, options
       b.request :url_encoded
       b.adapter :test do |stub|
         stub.post('/echo') do |env|
@@ -54,9 +55,10 @@
       part_bc, body_bc = result.part('b[c]')
       expect(part_bc).to_not be_nil
       expect(part_bc.filename).to eq('multipart_spec.rb')
-      expect(part_bc.headers['content-disposition']).to eq(
-        'form-data; foo=1; name="b[c]"; filename="multipart_spec.rb"'
-      )
+      expect(part_bc.headers['content-disposition'])
+        .to eq(
+              'form-data; foo=1; name="b[c]"; filename="multipart_spec.rb"'
+            )
       expect(part_bc.headers['content-type']).to eq('text/x-ruby')
       expect(part_bc.headers['content-transfer-encoding']).to eq('binary')
       expect(body_bc).to eq(File.read(__FILE__))
@@ -112,9 +114,9 @@
       {
         a: 1,
         b: [{
-          c: Faraday::FilePart.new(__FILE__, 'text/x-ruby'),
-          d: 2
-        }]
+              c: Faraday::FilePart.new(__FILE__, 'text/x-ruby'),
+              d: 2
+            }]
       }
     end
 
@@ -135,9 +137,10 @@
       part_bc, body_bc = result.part('b[][c]')
       expect(part_bc).to_not be_nil
       expect(part_bc.filename).to eq('multipart_spec.rb')
-      expect(part_bc.headers['content-disposition']).to eq(
-        'form-data; name="b[][c]"; filename="multipart_spec.rb"'
-      )
+      expect(part_bc.headers['content-disposition'])
+        .to eq(
+              'form-data; name="b[][c]"; filename="multipart_spec.rb"'
+            )
       expect(part_bc.headers['content-type']).to eq('text/x-ruby')
       expect(part_bc.headers['content-transfer-encoding']).to eq('binary')
       expect(body_bc).to eq(File.read(__FILE__))
@@ -177,9 +180,10 @@
       part_bc, body_bc = result.part('b[c]')
       expect(part_bc).to_not be_nil
       expect(part_bc.filename).to eq('multipart_spec.rb')
-      expect(part_bc.headers['content-disposition']).to eq(
-        'form-data; foo=1; name="b[c]"; filename="multipart_spec.rb"'
-      )
+      expect(part_bc.headers['content-disposition'])
+        .to eq(
+              'form-data; foo=1; name="b[c]"; filename="multipart_spec.rb"'
+            )
       expect(part_bc.headers['content-type']).to eq('text/x-ruby')
       expect(part_bc.headers['content-transfer-encoding']).to eq('binary')
       expect(body_bc).to eq(File.read(__FILE__))
@@ -235,9 +239,9 @@
       {
         a: 1,
         b: [{
-          c: Faraday::UploadIO.new(__FILE__, 'text/x-ruby'),
-          d: 2
-        }]
+              c: Faraday::UploadIO.new(__FILE__, 'text/x-ruby'),
+              d: 2
+            }]
       }
     end
 
@@ -258,9 +262,10 @@
       part_bc, body_bc = result.part('b[][c]')
       expect(part_bc).to_not be_nil
       expect(part_bc.filename).to eq('multipart_spec.rb')
-      expect(part_bc.headers['content-disposition']).to eq(
-        'form-data; name="b[][c]"; filename="multipart_spec.rb"'
-      )
+      expect(part_bc.headers['content-disposition'])
+        .to eq(
+              'form-data; name="b[][c]"; filename="multipart_spec.rb"'
+            )
       expect(part_bc.headers['content-type']).to eq('text/x-ruby')
       expect(part_bc.headers['content-transfer-encoding']).to eq('binary')
       expect(body_bc).to eq(File.read(__FILE__))
@@ -271,4 +276,27 @@
       expect(body_bd).to eq('2')
     end
   end
+
+  context 'when passing flat_encode=true option' do
+    let(:options) { { flat_encode: true } }
+    let(:io) { StringIO.new('io-content') }
+    let(:payload) do
+      {
+        a: 1,
+        b: [
+          Faraday::UploadIO.new(io, 'application/pdf'),
+          Faraday::UploadIO.new(io, 'application/pdf')
+        ]
+      }
+    end
+
+    it_behaves_like 'a multipart request'
+
+    it 'encode params using flat encoder' do
+      response = conn.post('/echo', payload)
+
+      expect(response.body).to include('name="b"')
+      expect(response.body).not_to include('name="b[]"')
+    end
+  end
 end