Fix typo in compiler flag generation

Author: ianfixes

Diff for: CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 - A missing `examples` directory no longer causes a crash in `cpp_library.rb`
 - Referring to an undefined platform no longer causes a crash; it's now a helpful error message
+- A copy/paste error that prevented compiler warning flags from being supplied has been fixed, via jgfoster
 
 ### Security
 

Diff for: lib/arduino_ci/cpp_library.rb

@@ -446,7 +446,7 @@ def feature_args(ci_gcc_config)
     def warning_args(ci_gcc_config)
       return [] if ci_gcc_config[:warnings].nil?
 
-      ci_gcc_config[:features].map { |w| "-W#{w}" }
+      ci_gcc_config[:warnings].map { |w| "-W#{w}" }
     end
 
     # GCC command line arguments for defines (e.g. -Dhave_something)

Diff for: spec/cpp_library_spec.rb

@@ -76,6 +76,32 @@ def verified_install(backend, path)
 RSpec.describe ArduinoCI::CppLibrary do
   next if skip_ruby_tests
 
+  context "compiler flags" do
+    config = ArduinoCI::CIConfig.new
+    config.load_yaml(File.join(File.dirname(__FILE__), "yaml", "o1.yaml"))
+    bogo_config = config.gcc_config("bogo")
+    fld = FakeLibDir.new
+    backend = fld.backend
+    cpp_lib_path = sampleproj_path + "DoSomething"
+    cpp_library = verified_install(backend, cpp_lib_path)
+
+    # the keys are the methods of cpp_library to call
+    # the results are what we expect to see based on the config we loaded
+    methods_and_results = {
+      feature_args: ["-fa", "-fb"],
+      warning_args: ["-We", "-Wf"],
+      define_args: ["-Dc", "-Dd"],
+      flag_args: ["g", "h"]
+    }
+
+    methods_and_results.each do |m, expected|
+      it "Creates #{m} from config" do
+        expect(expected).to eq(cpp_library.send(m, bogo_config))
+      end
+    end
+
+  end
+
   context "arduino-library-specification detection" do
 
     answers = {