Infer whether we need to publish Docker website port

Previously, users needed to explicitly specify and commandline parameter
in order to correctly serve the website locally. This change inspects
the task graph to see whether serving will be performed and
automatically adds the port publishing.

Author: swegner

website/README.md

@@ -37,7 +37,7 @@ run website tests.
 
 The following command is used to build and serve the website locally.
 
-    $ ./gradlew -PpublishJekyllPort :beam-website:serveWebsite
+    $ ./gradlew :beam-website:serveWebsite
 
 Any changes made locally will trigger a rebuild of the website.
 

website/build.gradle

@@ -64,12 +64,15 @@ task createDockerContainer(type: Exec) {
   ext.containerId = {
     return standardOutput.toString().trim()
   }
-  def extraOptions = ''
-  if (project.hasProperty('publishJekyllPort')) {
-    extraOptions = '-p 127.0.0.1:4000:4000'
+  gradle.taskGraph.whenReady {
+    def extraOptions = ''
+    if (gradle.taskGraph.hasTask(":${project.name}:serveWebsite")) {
+      // Publish port 4000 where Jekyll serves website from
+      extraOptions = '--publish 127.0.0.1:4000:4000'
+    }
+    commandLine '/bin/bash', '-c',
+      "docker create -v $project.rootDir:$dockerWorkDir -u \$(id -u):\$(id -g) $extraOptions $dockerImageTag"
   }
-  commandLine '/bin/bash', '-c',
-    "docker create -v $project.rootDir:$dockerWorkDir -u \$(id -u):\$(id -g) $extraOptions $dockerImageTag"
 }
 
 task startDockerContainer(type: Exec) {