Restore compatibility

.github/workflows/development.yml

@@ -15,6 +15,9 @@ jobs:
           - macos
 
         ruby:
+          - "2.3"
+          - "2.4"
+          - "2.5"
           - "2.6"
           - "2.7"
           - "3.0"
@@ -43,4 +46,6 @@ jobs:
 
     - name: Run tests
       timeout-minutes: 5
-      run: ${{matrix.env}} bundle exec rspec
+      run: |
+        gem update --system
+        ${{matrix.env}} bundle exec rspec

gems.rb

@@ -4,7 +4,9 @@
 
 gem "bake"
 
-group :maintenance, optional: true do
-	gem "bake-gem"
-	gem "bake-modernize"
+if RUBY_VERSION >= "2.7.0"
+	group :maintenance, optional: true do
+		gem "bake-gem"
+		gem "bake-modernize"
+	end
 end

lib/multipart/post/multipartable.rb

@@ -44,11 +44,10 @@ def self.secure_boundary
 
       def initialize(path, params, headers={}, boundary = Multipartable.secure_boundary)
         headers = headers.clone # don't want to modify the original variable
-        parts_headers = headers.delete(:parts) || {}
-        parts_headers.transform_keys!(&:to_sym)
+        parts_headers = symbolize_keys(headers.delete(:parts) || {})
 
         super(path, headers)
-        parts = params.transform_keys(&:to_sym).map do |k,v|
+        parts = symbolize_keys(params).map do |k,v|
           case v
           when Array
             v.map {|item| Parts::Part.new(boundary, k, item, parts_headers[k]) }
@@ -67,6 +66,18 @@ def initialize(path, params, headers={}, boundary = Multipartable.secure_boundar
       end
 
       attr :boundary
+
+      private
+
+      if RUBY_VERSION >= "2.5.0"
+        def symbolize_keys(hash)
+          hash.transform_keys(&:to_sym)
+        end
+      else
+        def symbolize_keys(hash)
+          hash.map{|key,value| [key.to_sym, value]}.to_h
+        end
+      end
     end
   end
 end

multipart-post.gemspec

@@ -10,16 +10,15 @@ Gem::Specification.new do |spec|
 	spec.authors = ["Nick Sieger", "Samuel Williams", "Olle Jonsson", "McClain Looney", "Lewis Cowles", "Gustav Ernberg", "Patrick Davey", "Steven Davidovitz", "Alex Koppel", "Ethan Turkeltaub", "Jagtesh Chadha", "Jason York", "Nick", "VincWebwag", "hasimo", "hexfet", "Christine Yen", "David Moles", "Eric Hutzelman", "Feuda Nan", "Gerrit Riessen", "Jan Piotrowski", "Jan-Joost Spanjers", "Jason Moore", "Jeff Hodges", "Johannes Wagener", "Jordi Massaguer Pla", "Lachlan Priest", "Leo Cassarani", "Lonre Wang", "Luke Redpath", "Matt Colyer", "Mislav Marohnić", "Socrates Vicente", "Steffen Grunwald", "Tim Barkley"]
 	spec.license = "MIT"
 
-	spec.required_ruby_version = ">= 2.6.0"
+	spec.required_ruby_version = ">= 2.3.0"
 
 	spec.cert_chain  = ['release.cert']
 	spec.signing_key = File.expand_path('~/.gem/release.pem')
 
 	spec.homepage = "https://github.com/socketry/multipart-post"
 
-	spec.files = Dir.glob('{lib}/**/*', File::FNM_DOTMATCH, base: __dir__)
+	spec.files = Dir.glob('{lib}/**/*', File::FNM_DOTMATCH)
 
 	spec.add_development_dependency "bundler"
-	spec.add_development_dependency "rake"
 	spec.add_development_dependency "rspec", "~> 3.4"
 end