druid/codestyle/checkstyle.xml

<?xml version="1.0" ?>

<!--
  ~ 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
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  ~ 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.
  -->

<!DOCTYPE module PUBLIC
    "-//Puppy Crawl//DTD Check Configuration 1.2//EN"
    "http://www.puppycrawl.com/dtds/configuration_1_2.dtd">

<module name="Checker">
  <module name="Header">
    <property name="headerFile" value="${checkstyle.header.file}"/>
    <property name="fileExtensions" value="java"/>
  </module>

  <module name="NewlineAtEndOfFile"/>
  <module name="FileTabCharacter"/>

  <module name="TreeWalker">
    <module name="SuppressionCommentFilter">
      <property name="offCommentFormat" value="CHECKSTYLE.OFF\: ([\w\|]+)"/>
      <property name="onCommentFormat" value="CHECKSTYLE.ON\: ([\w\|]+)"/>
      <property name="checkFormat" value="$1"/>
    </module>

    <module name="RedundantModifier">
      <property name="tokens" value="INTERFACE_DEF,ENUM_DEF,METHOD_DEF"/>
    </module>

    <!-- See http://checkstyle.sourceforge.net/checks.html for examples -->

    <!--<module name="LineLength">-->
      <!--<property name="max" value="120"/>-->
    <!--</module>-->
    <module name="AvoidStarImport"/>
    <module name="AvoidStaticImport"/>
    <module name="RedundantImport"/>
    <module name="UnusedImports" />
    <module name="NeedBraces"/>
    <module name="LeftCurly">
      <property name="option" value="nl"/>
      <property name="tokens" value="INTERFACE_DEF,CLASS_DEF,ANNOTATION_DEF,ENUM_DEF,CTOR_DEF,METHOD_DEF"/>
    </module>
    <module name="LeftCurly">
      <property name="option" value="eol"/>
      <property name="tokens" value="LITERAL_WHILE,LITERAL_TRY,LITERAL_CATCH,LITERAL_FINALLY,LITERAL_SYNCHRONIZED,LITERAL_SWITCH,LITERAL_DO,LITERAL_IF,LITERAL_ELSE,LITERAL_FOR,STATIC_INIT,LAMBDA,ENUM_CONSTANT_DEF"/>
    </module>
    <module name="RightCurly">
      <property name="option" value="same"/>
      <property name="tokens" value="LITERAL_IF,LITERAL_ELSE,LITERAL_DO"/>
    </module>
    <module name="RightCurly">
      <property name="option" value="alone"/>
      <property name="tokens" value="LITERAL_TRY,LITERAL_CATCH,LITERAL_FINALLY,CLASS_DEF,METHOD_DEF,CTOR_DEF,LITERAL_FOR,LITERAL_WHILE,STATIC_INIT,INSTANCE_INIT"/>
    </module>

    <module name="WhitespaceAfter"/>
    <module name="WhitespaceAround">
      <property name="allowEmptyConstructors" value="true"/>
      <property name="allowEmptyMethods" value="true"/>
      <property name="allowEmptyLambdas" value="true"/>
      <property name="allowEmptyTypes" value="true"/>
      <property name="ignoreEnhancedForColon" value="false"/>
    </module>
    <module name="ParenPad"/>
    <module name="SingleSpaceSeparator"/>
    <module name="NoWhitespaceBefore">
      <property name="tokens" value="COMMA,SEMI,POST_INC,POST_DEC,ELLIPSIS,METHOD_REF"/>
    </module>
    <module name="NoWhitespaceBefore">
      <property name="tokens" value="DOT"/>
      <property name="allowLineBreaks" value="true"/>
    </module>
    <module name="NoWhitespaceAfter"/>
    <module name="NoWhitespaceAfter">
      <property name="tokens" value="DOT"/>
      <property name="allowLineBreaks" value="false"/>
    </module>
    <module name="GenericWhitespace"/>

    <module name="EmptyLineSeparator">
      <property name="tokens" value="PACKAGE_DEF,IMPORT,STATIC_IMPORT,INTERFACE_DEF,STATIC_INIT,INSTANCE_INIT,CTOR_DEF,VARIABLE_DEF"/>
      <property name="allowNoEmptyLineBetweenFields" value="true"/>
      <property name="allowMultipleEmptyLinesInsideClassMembers" value="false"/>
    </module>

    <module name="Indentation">
      <property name="basicOffset" value="2"/>
      <property name="caseIndent" value="2"/>
    </module>

    <module name="MethodParamPad">
      <property name="allowLineBreaks" value="true"/>
    </module>
    <module name="OneStatementPerLine"/>
    <module name="EmptyStatement"/>

    <module name="ModifierOrder" />

    <module name="Regexp">
      <property name="format" value="com\.google\.common\.io\.Closer"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use org.apache.druid.java.util.common.io.Closer instead of Guava's Closer"/>
    </module>
    <module name="Regexp">
      <property name="format" value="^// {2}"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Don't commit IntelliJ-style commented code lines"/>
    </module>
    <module name="Regexp">
      <property name="format" value="/\*[^\*].*?\n(\s*\*.*?\n)*\s+\*/[\s\n]*(transient|volatile|strictfp|synchronized|native|abstract|class|interface|enum|static|private|public|protected|default|void|byte|char|short|int|float|long|double|[A-Z])"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Comments to classes and methods must be Javadoc comments"/>
    </module>
    <module name="Regexp">
      <property name="format" value="natural\(\)[\s\n]*\.[\s\n]*nullsFirst\(\)"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use Comparators.naturalNullsFirst() instead of Ordering.natural().nullsFirst()"/>
    </module>
    <module name="Regexp">
      <property name="format" value="Enums\.getIfPresent\("/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use GuavaUtils.getEnumIfPresent() instead of Enums.getIfPresent()"/>
    </module>
    <module name="Regexp">
      <property name="format" value="(Byte|Character|Short|Integer|Long|Float|Double)\.TYPE"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use primitive.class instead. But check twice that you don't actually need BoxedPrimitive.class instead of BoxedPrimitive.TYPE"/>
    </module>
    <module name="Regexp">
      <property name="format" value="Float\.MAX_VALUE"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use Float.POSITIVE_INFINITY"/>
    </module>
    <module name="Regexp">
      <property name="format" value="Float\.MIN_VALUE"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use Float.NEGATIVE_INFINITY"/>
    </module>
    <module name="Regexp">
      <property name="format" value="Double\.MAX_VALUE"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use Double.POSITIVE_INFINITY"/>
    </module>
    <module name="Regexp">
      <property name="format" value="Double\.MIN_VALUE"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use Double.NEGATIVE_INFINITY"/>
    </module>
    <module name="Regexp">
      <property name="format" value="com\.metamx\.common\.logger"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use org.apache.druid.java.util.common.logger.Logger instead"/>
    </module>

    <module name="Regexp">
      <!-- Couldn't check this in forbidden-apis, because javac replaces compile-time constants without refs. -->
      <property name="format" value="(Shorts|Chars|Ints|Longs|Floats|Doubles)\.BYTES"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use java.lang.Primitive.BYTES instead."/>
    </module>
    <!-- This regex should be replaced with an IntelliJ inspection when teamcity.jetbrains.com updates to at least IntelliJ 2018.1 (currently it uses 2017.2) -->
    <module name="Regexp">
      <property name="format" value='[a-z][a-zA-Z0-9_]*\.equals\((\"|[A-Z_]+\))'/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value='Use "string".equals(javaVar) and STRING_CONSTANT.equals(javaVar) instead of javaVar.equals("string") and javaVar.equals(STRING_CONSTANT)'/>
    </module>

    <module name="Regexp">
      <property name="format" value="toArray\([\s\n]*new [a-zA-Z0-9_]+\[[^0]"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value='Use toArray(new Object[0]) instead'/>
    </module>
    <module name="Regexp">
      <property name="format" value="Strings.emptyToNull"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use org.apache.druid.common.config.NullHandling.emptyToNullIfNeeded instead"/>
    </module>
    <module name="Regexp">
      <property name="format" value="Strings.nullToEmpty"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use org.apache.druid.common.config.NullHandling.nullToEmptyIfNeeded instead"/>
    </module>

    <module name="Regexp">
      <property name="format" value='@Produces\(\"text/plain\"\)'/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Use org.apache.druid.server.http.HttpMediaType#TEXT_PLAIN_UTF8 instead"/>
    </module>

    <module name="PackageName">
      <property name="format" value="^org.apache.druid.*$"/>
    </module>
    <module name="PackageDeclaration"/>

    <!-- See https://github.com/checkstyle/checkstyle/issues/5510 and the ImportOrder suppression in
         checkstyle-suppressions.xml -->
    <module name="ImportOrder">
      <property name="groups" value="*,javax,java"/>
      <property name="ordered" value="true"/>
      <property name="separated" value="true"/>
      <property name="option" value="bottom"/>
      <property name="sortStaticImportsAlphabetically" value="true"/>
    </module>

    <module name="Regexp">
      <property name="format" value="instanceof\s+(ObjectColumnSelector|LongColumnSelector|FloatColumnSelector|DoubleColumnSelector)"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="ObjectColumnSelector, LongColumnSelector, FloatColumnSelector
      and DoubleColumnSelector must not be used in an instanceof statement, see Javadoc of those interfaces."/>
    </module>

    <module name="Regexp">
      <property name="id" value="argumentLineBreaking"/>
      <property
          name="format"
          value='(?&lt;!ImmutableMap.of|Types.mapOf|orderedMap|makeSelectResults|makeListOfPairs)\(\s*\n +([^,\n\(\{"&lt;/]+|[^,\n\(\{" /]+&gt; [a-zA-Z0-9_]+)\, ++[^,\n/]+'
      />
      <property name="illegalPattern" value="true"/>
      <property name="message" value="&#10;
According to the Druid code style, if a method or constructor declaration or a call&#10;
doesn't fit a single line, each parameter or argument should be on it's own, e. g:&#10;
&#10;
    MyReturnType myMethodWithAVeryLongName(&#10;
        MyParamTypeA myParamAWithAVeryLongName,&#10;
        MyParamTypeB myParamBWithAVeryLongName&#10;
    )&#10;
&#10;
or&#10;
&#10;
    MyValueType myValue = myMethodWithAVeryLongName(&#10;
        myVeryLongArgA,&#10;
        myVeryLongArgB&#10;
    )&#10;
&#10;
The exceptions from this rule are map-like and pair-accepting constructors and methods,&#10;
for those it's preferred to put each pair on it's own line, e. g:&#10;
&#10;
    Map&lt;MyKeyType, MyValueType&gt; myMap = ImmutableMap.of(&#10;
        myKey1, myValue1,&#10;
        myKey2, myValue2&#10;
    )&#10;
&#10;
Always prefer to fit a declaration or a method or constructor call into a single line&#10;
(less than 120 cols), if possible.&#10;
&#10;
Two things to note to avoid unnecessary breakdown:&#10;
&#10;
1) Exceptions declared for a method could be broken to the next line separately, e. g:&#10;
&#10;
    MyReturnType myMethodWithAVeryLongName(MyParamTypeA myParamA, MyParamTypeB myParamB)&#10;
        throws MyExceptionTypeAWithVeryLongName, MyExceptionTypeBWithVeryLongName&#10;
&#10;
2) In a variable, field or constant assignment, it's often more readable to break the&#10;
whole right hand side expression to the next line, instead of breaking the expression&#10;
arguments, e. g:&#10;
&#10;
    MyTypeWithAVeryLongName myVariableWithAVeryLongName =&#10;
        myMethodWithAVeryLongName(myArgA, myArgB);&#10;
&#10;
Also note that this checkstyle rule (the one that caused this message to be printed)&#10;
doesn't spot all violations of the corresponding Druid code style rule. If you see&#10;
a place where method or constructor parameters or call arguments are not properly&#10;
located each on it's own line, but this checkstyle rule is silent, if doesn't mean&#10;
that the code is formatted correctly. Fix it anyway.&#10;
&#10;
If you encouter a map-like or a pair-accepting method that is reported by this&#10;
checkstyle rule, you should add it as an exception in the corresponding rule in&#10;
codestyle/checkstyle.xml.&#10;"/>
    </module>

    <module name="Regexp">
      <property name="id" value="duplicateLine"/>
      <property name="format" value="^(.*;)(\r?\n\1)+$"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Duplicate line"/>
    </module>
    
     <!-- Added as per the issue #6936 - Prohibit method names starting with capital letters -->
	 <module name="MethodName">
	   <property name = "format" value = "^[a-z_]*[a-z0-9][a-zA-Z0-9_]*$"/>
	 </module>
  </module>
</module>