SPARK-1096, a space after comment start style checker.

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #124 from ScrapCodes/SPARK-1096/scalastyle-comment-check and squashes the following commits:

214135a [Prashant Sharma] Review feedback.
5eba88c [Prashant Sharma] Fixed style checks for ///+ comments.
e54b2f8 [Prashant Sharma] improved message, work around.
83e7144 [Prashant Sharma] removed dependency on scalastyle in plugin, since scalastyle sbt plugin already depends on the right version. Incase we update the plugin we will have to adjust our spark-style project to depend on right scalastyle version.
810a1d6 [Prashant Sharma] SPARK-1096, a space after comment style checker.
ba33193 [Prashant Sharma] scala style as a project

4 files changed, 104 insertions, 3 deletions

diff --git a/project/SparkBuild.scala b/project/SparkBuild.scala
index 9e269e6551..2549bc9710 100644
--- a/project/SparkBuild.scala
+++ b/project/SparkBuild.scala
@@ -17,7 +17,7 @@
 
 import sbt._
 import sbt.Classpaths.publishTask
-import Keys._
+import sbt.Keys._
 import sbtassembly.Plugin._
 import AssemblyKeys._
 import scala.util.Properties
@@ -27,7 +27,7 @@ import com.typesafe.tools.mima.plugin.MimaKeys.previousArtifact
 import scala.collection.JavaConversions._
 
 // For Sonatype publishing
-//import com.jsuereth.pgp.sbtplugin.PgpKeys._
+// import com.jsuereth.pgp.sbtplugin.PgpKeys._
 
 object SparkBuild extends Build {
   val SPARK_VERSION = "1.0.0-SNAPSHOT" 
@@ -200,7 +200,7 @@ object SparkBuild extends Build {
 
     publishMavenStyle := true,
 
-    //useGpg in Global := true,
+    // useGpg in Global := true,
 
     pomExtra := (
       <parent>
diff --git a/project/plugins.sbt b/project/plugins.sbt
index 4ff6f67af4..5aa8a1ec24 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -22,3 +22,4 @@ addSbtPlugin("org.scalastyle" %% "scalastyle-sbt-plugin" % "0.4.0")
 addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.1.6")
 
 addSbtPlugin("com.alpinenow" % "junit_xml_listener" % "0.5.0")
+
diff --git a/project/project/SparkPluginBuild.scala b/project/project/SparkPluginBuild.scala
new file mode 100644
index 0000000000..43361aa2b4
--- /dev/null
+++ b/project/project/SparkPluginBuild.scala
@@ -0,0 +1,44 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import sbt._
+import sbt.Keys._
+
+/**
+ * This plugin project is there to define new scala style rules for spark. This is
+ * a plugin project so that this gets compiled first and is put on the classpath and
+ * becomes available for scalastyle sbt plugin.
+ */
+object SparkPluginDef extends Build {
+  lazy val root = Project("plugins", file(".")) dependsOn(sparkStyle)
+  lazy val sparkStyle = Project("spark-style", file("spark-style"), settings = styleSettings)
+  val sparkVersion = "1.0.0-SNAPSHOT"
+  // There is actually no need to publish this artifact.
+  def styleSettings = Defaults.defaultSettings ++ Seq (
+    name                 :=  "spark-style",
+    organization         :=  "org.apache.spark",
+    version              :=  sparkVersion,
+    scalaVersion         :=  "2.10.3",
+    scalacOptions        :=  Seq("-unchecked", "-deprecation"),
+    libraryDependencies  ++= Dependencies.scalaStyle,
+    sbtPlugin            :=  true
+  )
+
+  object Dependencies {
+    val scalaStyle = Seq("org.scalastyle" %% "scalastyle" % "0.4.0")
+  }
+}
diff --git a/project/spark-style/src/main/scala/org/apache/spark/scalastyle/SparkSpaceAfterCommentStyleCheck.scala b/project/spark-style/src/main/scala/org/apache/spark/scalastyle/SparkSpaceAfterCommentStyleCheck.scala
new file mode 100644
index 0000000000..2f3c1a1828
--- /dev/null
+++ b/project/spark-style/src/main/scala/org/apache/spark/scalastyle/SparkSpaceAfterCommentStyleCheck.scala
@@ -0,0 +1,56 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+package org.apache.spark.scalastyle
+
+import java.util.regex.Pattern
+
+import org.scalastyle.{PositionError, ScalariformChecker, ScalastyleError}
+import scalariform.lexer.{MultiLineComment, ScalaDocComment, SingleLineComment, Token}
+import scalariform.parser.CompilationUnit
+
+class SparkSpaceAfterCommentStartChecker extends ScalariformChecker {
+  val errorKey: String = "insert.a.single.space.after.comment.start"
+
+  private def multiLineCommentRegex(comment: Token) =
+    Pattern.compile( """/\*\S+.*""", Pattern.DOTALL).matcher(comment.text.trim).matches()
+
+  private def scalaDocPatternRegex(comment: Token) =
+    Pattern.compile( """/\*\*\S+.*""", Pattern.DOTALL).matcher(comment.text.trim).matches()
+
+  private def singleLineCommentRegex(comment: Token): Boolean =
+    comment.text.trim.matches( """//\S+.*""") && !comment.text.trim.matches( """///+""")
+
+  override def verify(ast: CompilationUnit): List[ScalastyleError] = {
+    ast.tokens
+      .filter(hasComment)
+      .map {
+      _.associatedWhitespaceAndComments.comments.map {
+        case x: SingleLineComment if singleLineCommentRegex(x.token) => Some(x.token.offset)
+        case x: MultiLineComment if multiLineCommentRegex(x.token) => Some(x.token.offset)
+        case x: ScalaDocComment if scalaDocPatternRegex(x.token) => Some(x.token.offset)
+        case _ => None
+      }.flatten
+    }.flatten.map(PositionError(_))
+  }
+
+
+  private def hasComment(x: Token) =
+    x.associatedWhitespaceAndComments != null && !x.associatedWhitespaceAndComments.comments.isEmpty
+
+}