Re-add support for Ruby 2.4+

.github/workflows/ci.yml

@@ -42,7 +42,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['2.6', '2.7', '3.0', '3.1']
+        ruby: ['2.4', '2.5', '2.6', '2.7', '3.0', '3.1']
 
     steps:
     - uses: actions/checkout@v1

.rubocop.yml

@@ -8,7 +8,7 @@ require:
 AllCops:
   DisplayCopNames: true
   DisplayStyleGuide: true
-  TargetRubyVersion: 2.6
+  TargetRubyVersion: 2.4
 
 Inclusivity/Race:
   Enabled: true

faraday.gemspec

@@ -13,7 +13,7 @@ Gem::Specification.new do |spec| # rubocop:disable Metrics/BlockLength
   spec.homepage = 'https://lostisland.github.io/faraday'
   spec.licenses = ['MIT']
 
-  spec.required_ruby_version = '>= 2.6'
+  spec.required_ruby_version = '>= 2.4'
 
   spec.add_dependency 'faraday-em_http', '~> 1.0'
   spec.add_dependency 'faraday-em_synchrony', '~> 1.0'

spec/faraday/request/instrumentation_spec.rb

@@ -30,11 +30,13 @@ def instrument(name, env)
 
   it { expect(options.name).to eq('request.faraday') }
   it 'defaults to ActiveSupport::Notifications' do
-    res = options.instrumenter
-  rescue NameError => e
-    expect(e.to_s).to match('ActiveSupport')
-  else
-    expect(res).to eq(ActiveSupport::Notifications)
+    begin
+      res = options.instrumenter
+    rescue NameError => e
+      expect(e.to_s).to match('ActiveSupport')
+    else
+      expect(res).to eq(ActiveSupport::Notifications)
+    end
   end
 
   it 'instruments with default name' do

spec/support/webmock_rack_app.rb

@@ -41,7 +41,8 @@ def req_uri(env)
 
   def req_headers(env)
     http_headers = env.select { |k, _| k.start_with?('HTTP_') }
-                      .transform_keys { |k| k[5..] }
+                      .map { |k, v| [k[5..-1], v] }
+                      .to_h
 
     special_headers = Faraday::Adapter::Rack::SPECIAL_HEADERS
     http_headers.merge(env.select { |k, _| special_headers.include?(k) })