Handle simpler and invalid values for config overrides

lib/java_buildpack/util/configuration_utils.rb

@@ -42,17 +42,8 @@ def load(identifier, should_log = true)
           file = CONFIG_DIRECTORY + "#{identifier}.yml"
 
           if file.exist?
-            configuration = YAML.load_file(file)
-            logger.debug { "Configuration from #{file}: #{configuration}" } if should_log
-
             user_provided = ENV[environment_variable_name(identifier)]
-
-            if user_provided
-              YAML.load(user_provided).each do |new_prop|
-                configuration = do_merge(configuration, new_prop, should_log)
-              end
-              logger.debug { "Configuration from #{file} modified with: #{user_provided}" } if should_log
-            end
+            configuration = load_configuration(file, user_provided, should_log)
           else
             logger.debug { "No configuration file #{file} found" } if should_log
           end
@@ -68,6 +59,27 @@ def load(identifier, should_log = true)
 
         private_constant :CONFIG_DIRECTORY, :ENVIRONMENT_VARIABLE_PATTERN
 
+        def load_configuration(file, user_provided, should_log)
+          configuration = YAML.load_file(file)
+          logger.debug { "Configuration from #{file}: #{configuration}" } if should_log
+
+          if user_provided
+            user_provided_value = YAML.load(user_provided)
+            if user_provided_value.is_a?(Hash)
+              configuration = do_merge(configuration, user_provided_value, should_log)
+            elsif user_provided_value.is_a?(Array)
+              user_provided_value.each do |new_prop|
+                configuration = do_merge(configuration, new_prop, should_log)
+              end
+            else
+              fail "User configuration value is not valid: #{user_provided_value}"
+            end
+            logger.debug { "Configuration from #{file} modified with: #{user_provided}" } if should_log
+          end
+
+          configuration
+        end
+
         def do_merge(hash_v1, hash_v2, should_log)
           hash_v2.each do |key, value|
             if hash_v1.key? key

spec/java_buildpack/util/configuration_utils_spec.rb

@@ -34,12 +34,14 @@
     before do
       allow_any_instance_of(Pathname).to receive(:exist?).and_return(true)
       allow(YAML).to receive(:load_file).and_return('foo' => { 'one' => '1', 'two' => 2 },
-                                                    'bar' => { 'alpha' => { 'one' => 'cat', 'two' => 'dog' } })
+                                                    'bar' => { 'alpha' => { 'one' => 'cat', 'two' => 'dog' } },
+                                                    'version' => '1.7.1')
     end
 
     it 'load configuration file' do
       expect(described_class.load('test')).to eq('foo' => { 'one' => '1', 'two' => 2 },
-                                                 'bar' => { 'alpha' => { 'one' => 'cat', 'two' => 'dog' } })
+                                                 'bar' => { 'alpha' => { 'one' => 'cat', 'two' => 'dog' } },
+                                                 'version' => '1.7.1')
     end
 
     context do
@@ -51,7 +53,34 @@
       it 'overlays matching environment variables' do
 
         expect(described_class.load('test')).to eq('foo' => { 'one' => '1', 'two' => 2 },
-                                                   'bar' => { 'alpha' => { 'one' => 3, 'two' => 'dog' } })
+                                                   'bar' => { 'alpha' => { 'one' => 3, 'two' => 'dog' } },
+                                                   'version' => '1.7.1')
+      end
+
+    end
+
+    context do
+
+      let(:environment) do
+        { 'JBP_CONFIG_TEST' => 'version: 1.8.+' }
+      end
+
+      it 'overlays simple matching environment variable' do
+        expect(described_class.load('test')).to eq('foo' => { 'one' => '1', 'two' => 2 },
+                                                   'bar' => { 'alpha' => { 'one' => 'cat', 'two' => 'dog' } },
+                                                   'version' => '1.8.+')
+      end
+
+    end
+
+    context do
+
+      let(:environment) do
+        { 'JBP_CONFIG_TEST' => 'version 1.8.+' }
+      end
+
+      it 'raises an exception when invalid override value is specified' do
+        expect { described_class.load('test') }.to raise_error(/User configuration value is not valid/)
       end
 
     end