[SPARK-7986] Split scalastyle config into 3 sections.

(1) rules that we enforce.
(2) rules that we would like to enforce, but haven't cleaned up the codebase to
    turn on yet (or we need to make the scalastyle rule more configurable).
(3) rules that we don't want to enforce.

Author: Reynold Xin <rxin@databricks.com>

Closes #6543 from rxin/scalastyle and squashes the following commits:

beefaab [Reynold Xin] [SPARK-7986] Split scalastyle config into 3 sections.

1 files changed, 174 insertions, 116 deletions

diff --git a/scalastyle-config.xml b/scalastyle-config.xml
index f52b09551a..d6f927b6fa 100644
--- a/scalastyle-config.xml
+++ b/scalastyle-config.xml
@@ -14,25 +14,41 @@
   ~ See the License for the specific language governing permissions and
   ~ limitations under the License.
   -->
-<!-- If you wish to turn off checking for a section of code, you can put a comment in the source
- before and after the section, with the following syntax: -->
-<!-- // scalastyle:off -->
-<!-- ... -->
-<!-- // naughty stuff -->
-<!-- ... -->
-<!-- // scalastyle:on -->
+<!--
+
+If you wish to turn off checking for a section of code, you can put a comment in the source
+before and after the section, with the following syntax:
+
+  // scalastyle:off
+  ...  // stuff that breaks the styles
+  // scalastyle:on
+
+You can also disable only one rule, by specifying its rule id, as specified in:
+  http://www.scalastyle.org/rules-0.7.0.html
+
+  // scalastyle:off no.finalize
+  override def finalize(): Unit = ...
+  // scalastyle:on no.finalize
+
+This file is divided into 3 sections:
+ (1) rules that we enforce.
+ (2) rules that we would like to enforce, but haven't cleaned up the codebase to turn on yet
+     (or we need to make the scalastyle rule more configurable).
+ (3) rules that we don't want to enforce.
+-->
 
 <scalastyle>
- <name>Scalastyle standard configuration</name>
- <check level="error" class="org.scalastyle.file.FileTabChecker" enabled="true"></check>
- <!-- <check level="error" class="org.scalastyle.file.FileLengthChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maxFileLength"><![CDATA[800]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <check level="error" class="org.scalastyle.file.HeaderMatchesChecker" enabled="true">
-  <parameters>
-   <parameter name="header"><![CDATA[/*
+  <name>Scalastyle standard configuration</name>
+
+  <!-- ================================================================================ -->
+  <!--                               rules we enforce                                   -->
+  <!-- ================================================================================ -->
+
+  <check level="error" class="org.scalastyle.file.FileTabChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.file.HeaderMatchesChecker" enabled="true">
+    <parameters>
+       <parameter name="header"><![CDATA[/*
  * 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.
@@ -48,122 +64,164 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */]]></parameter>
-  </parameters>
- </check>
+    </parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.SpacesAfterPlusChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.SpacesBeforePlusChecker" enabled="true"></check>
 
   <check level="error" class="org.scalastyle.file.WhitespaceEndOfLineChecker" enabled="true"></check>
 
- <check level="error" class="org.scalastyle.scalariform.SpacesAfterPlusChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.scalariform.SpacesBeforePlusChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.file.WhitespaceEndOfLineChecker" enabled="false"></check>
- <check level="error" class="org.scalastyle.file.FileLineLengthChecker" enabled="true">
-  <parameters>
-   <parameter name="maxLineLength"><![CDATA[100]]></parameter>
-   <parameter name="tabSize"><![CDATA[2]]></parameter>
-   <parameter name="ignoreImports">true</parameter>
-  </parameters>
- </check>
- <check level="error" class="org.scalastyle.scalariform.ClassNamesChecker" enabled="true">
-  <parameters>
-   <parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter>
-  </parameters>
- </check>
- <check level="error" class="org.scalastyle.scalariform.ObjectNamesChecker" enabled="true">
-  <parameters>
-   <parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter>
-  </parameters>
- </check>
- <check level="error" class="org.scalastyle.scalariform.PackageObjectNamesChecker" enabled="true">
-  <parameters>
-   <parameter name="regex"><![CDATA[^[a-z][A-Za-z]*$]]></parameter>
-  </parameters>
- </check>
- <check level="error" class="org.scalastyle.scalariform.EqualsHashCodeChecker" enabled="false"></check>
- <!-- <check level="error" class="org.scalastyle.scalariform.IllegalImportsChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="illegalImports"><![CDATA[sun._,java.awt._]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <check level="error" class="org.scalastyle.scalariform.ParameterNumberChecker" enabled="true">
-  <parameters>
-   <parameter name="maxParameters"><![CDATA[10]]></parameter>
-  </parameters>
- </check>
- <!-- <check level="error" class="org.scalastyle.scalariform.MagicNumberChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="ignore"><![CDATA[-1,0,1,2,3]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <check level="error" class="org.scalastyle.scalariform.NoWhitespaceBeforeLeftBracketChecker" enabled="false"></check>
- <check level="error" class="org.scalastyle.scalariform.NoWhitespaceAfterLeftBracketChecker" enabled="false"></check>
- <!-- <check level="error" class="org.scalastyle.scalariform.ReturnChecker" enabled="true"></check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.NullChecker" enabled="true"></check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.NoCloneChecker" enabled="true"></check> -->
+  <check level="error" class="org.scalastyle.file.FileLineLengthChecker" enabled="true">
+    <parameters>
+      <parameter name="maxLineLength"><![CDATA[100]]></parameter>
+      <parameter name="tabSize"><![CDATA[2]]></parameter>
+      <parameter name="ignoreImports">true</parameter>
+    </parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.ClassNamesChecker" enabled="true">
+    <parameters><parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter></parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.ObjectNamesChecker" enabled="true">
+    <parameters><parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter></parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.PackageObjectNamesChecker" enabled="true">
+    <parameters><parameter name="regex"><![CDATA[^[a-z][A-Za-z]*$]]></parameter></parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.ParameterNumberChecker" enabled="true">
+    <parameters><parameter name="maxParameters"><![CDATA[10]]></parameter></parameters>
+  </check>
+
   <check level="error" class="org.scalastyle.scalariform.NoFinalizeChecker" enabled="true"></check>
+
   <check level="error" class="org.scalastyle.scalariform.CovariantEqualsChecker" enabled="true"></check>
- <!-- <check level="error" class="org.scalastyle.scalariform.StructuralTypeChecker" enabled="true"></check> -->
- <!-- <check level="error" class="org.scalastyle.file.RegexChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="regex"><![CDATA[println]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.NumberOfTypesChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maxTypes"><![CDATA[30]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.CyclomaticComplexityChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maximum"><![CDATA[10]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
 
   <check level="error" class="org.scalastyle.scalariform.StructuralTypeChecker" enabled="true"></check>
 
- <check level="error" class="org.scalastyle.scalariform.UppercaseLChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.scalariform.SimplifyBooleanExpressionChecker" enabled="false"></check>
- <check level="error" class="org.scalastyle.scalariform.IfBraceChecker" enabled="true">
-  <parameters>
-   <parameter name="singleLineAllowed"><![CDATA[true]]></parameter>
-   <parameter name="doubleLineAllowed"><![CDATA[true]]></parameter>
-  </parameters>
- </check>
- <!-- <check level="error" class="org.scalastyle.scalariform.MethodLengthChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maxLength"><![CDATA[50]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.MethodNamesChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="regex"><![CDATA[^[a-z][A-Za-z0-9]*$]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.NumberOfMethodsInTypeChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maxMethods"><![CDATA[30]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <check level="error" class="org.scalastyle.scalariform.PublicMethodsHaveTypeChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.file.NewLineAtEofChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.file.NoNewLineAtEofChecker" enabled="false"></check>
- <check level="error" class="org.scalastyle.scalariform.NonASCIICharacterChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.scalariform.SpaceAfterCommentStartChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.scalariform.EnsureSingleSpaceBeforeTokenChecker" enabled="true">
+  <check level="error" class="org.scalastyle.scalariform.UppercaseLChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.IfBraceChecker" enabled="true">
+    <parameters>
+      <parameter name="singleLineAllowed"><![CDATA[true]]></parameter>
+      <parameter name="doubleLineAllowed"><![CDATA[true]]></parameter>
+    </parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.PublicMethodsHaveTypeChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.file.NewLineAtEofChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.NonASCIICharacterChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.SpaceAfterCommentStartChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.EnsureSingleSpaceBeforeTokenChecker" enabled="true">
    <parameters>
      <parameter name="tokens">ARROW, EQUALS, ELSE, TRY, CATCH, FINALLY, LARROW, RARROW</parameter>
    </parameters>
- </check>
+  </check>
+
   <check level="error" class="org.scalastyle.scalariform.EnsureSingleSpaceAfterTokenChecker" enabled="true">
     <parameters>
      <parameter name="tokens">ARROW, EQUALS, COMMA, COLON, IF, ELSE, DO, WHILE, FOR, MATCH, TRY, CATCH, FINALLY, LARROW, RARROW</parameter>
     </parameters>
   </check>
+
+  <!-- ??? usually shouldn't be checked into the code base. -->
   <check level="error" class="org.scalastyle.scalariform.NotImplementedErrorUsage" enabled="true"></check>
+
   <!-- As of SPARK-7558, all tests in Spark should extend o.a.s.SparkFunSuite instead of FunSuite directly -->
-  <check level="error" class="org.scalastyle.scalariform.TokenChecker" enabled="true">
-   <parameters>
-    <parameter name="regex">^FunSuite[A-Za-z]*$</parameter>
-   </parameters>
-   <customMessage>Tests must extend org.apache.spark.SparkFunSuite instead.</customMessage>
+  <check customId="funsuite" level="error" class="org.scalastyle.scalariform.TokenChecker" enabled="true">
+    <parameters><parameter name="regex">^FunSuite[A-Za-z]*$</parameter></parameters>
+    <customMessage>Tests must extend org.apache.spark.SparkFunSuite instead.</customMessage>
+  </check>
+
+  <!-- ================================================================================ -->
+  <!--       rules we'd like to enforce, but haven't cleaned up the codebase yet        -->
+  <!-- ================================================================================ -->
+
+  <!-- SPARK-7977 We should turn this on, but we'd need to add whitelist to files that are using it first. -->
+  <check customId="println" level="error" class="org.scalastyle.scalariform.TokenChecker" enabled="false">
+    <parameters><parameter name="regex">^println$</parameter></parameters>
+    <customMessage><![CDATA[Are you sure you want to println? If yes, wrap the code block with
+      // scalastyle:off println
+      println(...)
+      // scalastyle:on println]]></customMessage>
+  </check>
+
+  <!-- We cannot turn the following two on, because it'd fail a lot of string interpolation use cases. -->
+  <!-- Ideally the following two rules should be configurable to rule out string interpolation. -->
+  <check level="error" class="org.scalastyle.scalariform.NoWhitespaceBeforeLeftBracketChecker" enabled="false"></check>
+  <check level="error" class="org.scalastyle.scalariform.NoWhitespaceAfterLeftBracketChecker" enabled="false"></check>
+
+  <!-- This breaks symbolic method names so we don't turn it on. -->
+  <!-- Maybe we should update it to allow basic symbolic names, and then we are good to go. -->
+  <check level="error" class="org.scalastyle.scalariform.MethodNamesChecker" enabled="false">
+    <parameters>
+    <parameter name="regex"><![CDATA[^[a-z][A-Za-z0-9]*$]]></parameter>
+    </parameters>
+  </check>
+
+  <!-- Should turn this on, but we have a few places that need to be fixed first -->
+  <check level="error" class="org.scalastyle.scalariform.EqualsHashCodeChecker" enabled="false"></check>
+
+  <!-- ================================================================================ -->
+  <!--                               rules we don't want                                -->
+  <!-- ================================================================================ -->
+
+  <check level="error" class="org.scalastyle.scalariform.IllegalImportsChecker" enabled="false">
+    <parameters><parameter name="illegalImports"><![CDATA[sun._,java.awt._]]></parameter></parameters>
   </check>
+
+  <!-- We want the opposite of this: NewLineAtEofChecker -->
+  <check level="error" class="org.scalastyle.file.NoNewLineAtEofChecker" enabled="false"></check>
+
+  <!-- This one complains about all kinds of random things. Disable. -->
+  <check level="error" class="org.scalastyle.scalariform.SimplifyBooleanExpressionChecker" enabled="false"></check>
+
+  <!-- We use return quite a bit for control flows and guards -->
+  <check level="error" class="org.scalastyle.scalariform.ReturnChecker" enabled="false"></check>
+
+  <!-- We use null a lot in low level code and to interface with 3rd party code -->
+  <check level="error" class="org.scalastyle.scalariform.NullChecker" enabled="false"></check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.scalariform.NoCloneChecker" enabled="false"></check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.file.FileLengthChecker" enabled="false">
+    <parameters><parameter name="maxFileLength">800></parameter></parameters>
+  </check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.scalariform.NumberOfTypesChecker" enabled="false">
+    <parameters><parameter name="maxTypes">30</parameter></parameters>
+  </check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.scalariform.CyclomaticComplexityChecker" enabled="false">
+    <parameters><parameter name="maximum">10</parameter></parameters>
+  </check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.scalariform.MethodLengthChecker" enabled="false">
+    <parameters><parameter name="maxLength">50</parameter></parameters>
+  </check>
+
+  <!-- Not exactly feasible to enforce this right now. -->
+  <!-- It is also infrequent that somebody introduces a new class with a lot of methods. -->
+  <check level="error" class="org.scalastyle.scalariform.NumberOfMethodsInTypeChecker" enabled="false">
+    <parameters><parameter name="maxMethods"><![CDATA[30]]></parameter></parameters>
+  </check>
+
+  <!-- Doesn't seem super big deal here, and we have a lot of magic numbers ... -->
+  <check level="error" class="org.scalastyle.scalariform.MagicNumberChecker" enabled="false">
+    <parameters><parameter name="ignore">-1,0,1,2,3</parameter></parameters>
+  </check>
+
 </scalastyle>