Add Flag to Disable JRebel

This change adds a flag to the JRebel configuration that allows users to
explicitly disable the JRebel framework.

[resolves #457]

Author: dmitri-gb

config/jrebel_agent.yml

@@ -17,3 +17,4 @@
 ---
 version: 7.+
 repository_root: https://dl.zeroturnaround.com/jrebel
+enabled: true

docs/framework-jrebel_agent.md

@@ -25,6 +25,7 @@ The framework can be configured by modifying the [`config/jrebel_agent.yml`][] f
 | ---- | -----------
 | `repository_root` | The URL of the JRebel repository index ([details][repositories]).
 | `version` | The version of JRebel to use. Candidate versions can be found in [this listing][].
+| `enabled` | Whether to activate JRebel (upon the presence of `rebel-remote.xml`) or not.
 
 [Configuration and Extension]: ../README.md#configuration-and-extension
 [`config/jrebel_agent.yml`]: ../config/jrebel_agent.yml

lib/java_buildpack/framework/jrebel_agent.rb

@@ -46,8 +46,10 @@ def release
 
       # (see JavaBuildpack::Component::VersionedDependencyComponent#supports?)
       def supports?
-        jrebel_configured?(@application.root) || jrebel_configured?(@application.root + 'WEB-INF/classes') ||
-          jars_with_jrebel_configured?(@application.root)
+        enabled? && (
+            jrebel_configured?(@application.root) ||
+            jrebel_configured?(@application.root + 'WEB-INF/classes') ||
+            jars_with_jrebel_configured?(@application.root))
       end
 
       private
@@ -68,6 +70,10 @@ def architecture
         `uname -m`.strip
       end
 
+      def enabled?
+        @configuration['enabled'].nil? || @configuration['enabled']
+      end
+
     end
 
   end

spec/java_buildpack/framework/jrebel_agent_spec.rb

@@ -39,6 +39,15 @@
     expect(component.detect).to eq("jrebel-agent=#{version}")
   end
 
+  context do
+    let(:configuration) { { 'enabled' => false } }
+
+    it 'does not detect when not enabled',
+       app_fixture: 'framework_jrebel_app_simple' do
+      expect(component.detect).to be_nil
+    end
+  end
+
   it 'downloads the JRebel JAR and the native agent',
      app_fixture: 'framework_jrebel_app_simple',
      cache_fixture: 'stub-jrebel-archive.zip' do