checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
  Copyright © 2020 Cask Data, Inc.
  Licensed 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.
  -->

<!DOCTYPE module PUBLIC
        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
        "https://checkstyle.org/dtds/configuration_1_3.dtd">

<!-- This is a checkstyle configuration file. For descriptions of
what the following rules do, please see the checkstyle configuration
page at http://checkstyle.sourceforge.net/config.html -->

<module name="Checker">

    <module name="FileTabCharacter">
        <property name="severity" value="error"/>
        <!-- Checks that there are no tab characters in the file.
        -->
    </module>

    <!--
    LENGTH CHECKS FOR FILES
    -->

    <module name="FileLength">
        <property name="max" value="3000"/>
        <property name="severity" value="warning"/>
    </module>


    <module name="NewlineAtEndOfFile">
        <property name="lineSeparator" value="lf"/>
    </module>

    <module name="RegexpSingleline">
        <!-- Checks that FIXME is not used in comments.  TODO is preferred.
        -->
        <property name="format" value="((//.*)|(\*.*))FIXME" />
        <property name="message" value='TODO is preferred to FIXME.  e.g. "TODO: (ENG-123) -  Refactor when v2 is released."' />
    </module>

    <module name="RegexpSingleline">
        <!-- Checks that TODOs are named with some basic formatting. Checks for the following pattern  TODO: (
        -->
        <property name="format" value="((//.*)|(\*.*))TODO[^: (]" />
        <property name="message" value='All TODOs should be named.  e.g. "TODO: (ENG-123) - Refactor when v2 is released."' />
    </module>

    <module name="JavadocPackage">
        <!-- Checks that each Java package has a Javadoc file used for commenting.
          Only allows a package-info.java, not package.html. -->
        <property name="severity" value="error"/>
    </module>

    <!-- All Java AST specific tests live under TreeWalker module. -->
    <module name="TreeWalker">

        <!-- required for SupressionCommentFilter and SuppressWithNearbyCommentFilter -->
        <!--
        IMPORT CHECKS
        -->
        <module name="SuppressionCommentFilter">
          <property name="offCommentFormat" value="CHECKSTYLE OFF: (.+)" />
          <property name="onCommentFormat" value="CHECKSTYLE ON" />
          <property name="checkFormat" value="Javadoc.*"/>
          <property name="messageFormat" value="$1"/>
        </module>

        <module name="AvoidStarImport">
            <property name="allowClassImports" value="false"/>
            <property name="severity" value="error"/>
        </module>

        <module name="RedundantImport">
            <!-- Checks for redundant import statements. -->
            <property name="severity" value="error"/>
        </module>

        <module name="ImportOrder">
            <!-- Checks for out of order import statements. -->
            <property name="severity" value="error"/>
            <property name="ordered" value="true"/>
            <property name="groups" value="/([^j]|.[^a]|..[^v]|...[^a])/,/^javax?\./"/>
            <!-- This ensures that static imports go to the end. -->
            <property name="option" value="bottom"/>
            <property name="tokens" value="STATIC_IMPORT, IMPORT"/>
        </module>

        <module name="IllegalImport">
            <property name="illegalPkgs" value="junit.framework"/>
        </module>

        <!--
        METHOD LENGTH CHECKS
        -->

        <module name="MethodLength">
            <property name="tokens" value="METHOD_DEF"/>
            <property name="max" value="300"/>
            <property name="countEmpty" value="false"/>
            <property name="severity" value="warning"/>
        </module>

        <!--
        JAVADOC CHECKS
        -->

        <!-- Checks for Javadoc comments.                     -->
        <!-- See http://checkstyle.sf.net/config_javadoc.html -->
        <module name="JavadocMethod">
            <property name="scope" value="protected"/>
            <property name="severity" value="error"/>
            <property name="allowMissingJavadoc" value="true"/>
            <property name="allowMissingParamTags" value="true"/>
            <property name="allowMissingReturnTag" value="true"/>
            <property name="allowMissingThrowsTags" value="true"/>
            <property name="allowThrowsTagsForSubclasses" value="true"/>
            <property name="allowUndeclaredRTE" value="true"/>
        </module>

        <module name="JavadocType">
            <property name="scope" value="protected"/>
            <property name="severity" value="error"/>
        </module>

        <module name="JavadocStyle">
            <property name="severity" value="error"/>
        </module>

        <!--
        NAMING CHECKS
        -->

        <!-- Item 38 - Adhere to generally accepted naming conventions -->

        <module name="PackageName">
            <!-- Validates identifiers for package names against the
              supplied expression. -->
            <!-- Here the default checkstyle rule restricts package name parts to
              seven characters, this is not in line with common practice at Google.
            -->
            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]{1,})*$"/>
            <property name="severity" value="error"/>
        </module>

        <module name="TypeNameCheck">
            <!-- Validates static, final fields against the
            expression "^[A-Z][a-zA-Z0-9]*$". -->
            <metadata name="altname" value="TypeName"/>
            <property name="severity" value="error"/>
        </module>

        <module name="ConstantNameCheck">
            <!-- Validates non-private, static, final fields against the supplied
            public/package final fields "^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$". -->
            <metadata name="altname" value="ConstantName"/>
            <property name="applyToPublic" value="true"/>
            <property name="applyToProtected" value="true"/>
            <property name="applyToPackage" value="true"/>
            <property name="applyToPrivate" value="false"/>
            <property name="format" value="^([A-Z][A-Z0-9]*(_[A-Z0-9]+)*|FLAG_.*)$"/>
            <message key="name.invalidPattern"
                     value="Variable ''{0}'' should be in ALL_CAPS (if it is a constant) or be private (otherwise)."/>
            <property name="severity" value="error"/>
        </module>

        <module name="StaticVariableNameCheck">
            <!-- Validates static, non-final fields against the supplied
            expression "^[a-z][a-zA-Z0-9]*_?$". -->
            <metadata name="altname" value="StaticVariableName"/>
            <property name="applyToPublic" value="true"/>
            <property name="applyToProtected" value="true"/>
            <property name="applyToPackage" value="true"/>
            <property name="applyToPrivate" value="true"/>
            <property name="format" value="^[a-z][a-zA-Z0-9]*_?$"/>
            <property name="severity" value="error"/>
        </module>

        <module name="MemberNameCheck">
            <!-- Validates non-static members against the supplied expression. -->
            <metadata name="altname" value="MemberName"/>
            <property name="applyToPublic" value="true"/>
            <property name="applyToProtected" value="true"/>
            <property name="applyToPackage" value="true"/>
            <property name="applyToPrivate" value="true"/>
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
            <property name="severity" value="error"/>
        </module>

        <module name="MethodNameCheck">
            <!-- Validates identifiers for method names. -->
            <metadata name="altname" value="MethodName"/>
            <property name="format" value="^[a-z][a-zA-Z0-9]*(_[a-zA-Z0-9]+)*$"/>
            <property name="severity" value="error"/>
        </module>

        <module name="ParameterName">
            <!-- Validates identifiers for method parameters against the
              expression "^[a-z][a-zA-Z0-9]*$". -->
            <property name="severity" value="error"/>
        </module>

        <module name="LocalFinalVariableName">
            <!-- Validates identifiers for local final variables against the
              expression "^[a-z][a-zA-Z0-9]*$". -->
            <property name="severity" value="error"/>
        </module>

        <module name="LocalVariableName">
            <!-- Validates identifiers for local variables against the
              expression "^[a-z][a-zA-Z0-9]*$". -->
            <property name="severity" value="error"/>
        </module>


        <!--
        LENGTH and CODING CHECKS
        -->

        <module name="LineLength">
            <!-- Checks if a line is too long. -->
            <property name="max" value="120" default="120"/>
            <property name="severity" value="error"/>

            <!--
              The default ignore pattern exempts the following elements:
                - import statements
                - long URLs inside comments
            -->

            <property name="ignorePattern"
                      value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.ignorePattern}"
                      default="^(package .*;\s*)|(import .*;\s*)|( *\* *https?://.*)$"/>
        </module>

        <module name="LeftCurly">
            <!-- Checks for placement of the left curly brace ('{'). -->
            <property name="severity" value="error"/>
        </module>

        <module name="RightCurly">
            <!-- Checks right curlies on CATCH, ELSE, and TRY blocks are on
            the same line. e.g., the following example is fine:
            <pre>
              if {
                ...
              } else
            </pre>
            -->
            <!-- This next example is not fine:
            <pre>
              if {
                ...
              }
              else
            </pre>
            -->
            <property name="option" value="same"/>
            <property name="severity" value="error"/>
        </module>

        <!-- Checks for braces around if and else blocks -->
        <module name="NeedBraces">
            <property name="severity" value="error"/>
            <property name="tokens" value="LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO"/>
        </module>

        <module name="UpperEll">
            <!-- Checks that long constants are defined with an upper ell.-->
            <property name="severity" value="error"/>
        </module>

        <module name="FallThrough">
            <!-- Warn about falling through to the next case statement.  Similar to
            javac -Xlint:fallthrough, but the check is suppressed if a single-line comment
            on the last non-blank line preceding the fallen-into case contains 'fall through' (or
            some other variants which we don't publicized to promote consistency).
            -->
            <property name="reliefPattern"
                      value="fall through|Fall through|fallthru|Fallthru|falls through|Falls through|fallthrough|Fallthrough|No break|NO break|no break|continue on"/>
            <property name="severity" value="error"/>
        </module>


        <!--
        MODIFIERS CHECKS
        -->

        <module name="ModifierOrder">
            <!-- Warn if modifier order is inconsistent with JLS3 8.1.1, 8.3.1, and
                 8.4.3.  The prescribed order is:
                 public, protected, private, abstract, static, final, transient, volatile,
                 synchronized, native, strictfp
              -->
        </module>

        <module name="RedundantModifier">
            <!-- Checks for redundant modifiers in:
                 - interface and annotation definitions,
                 - the final modifier on methods of final classes, and
                 - inner interface declarations that are declared as static.
              -->
        </module>


        <!--
        WHITESPACE CHECKS
        -->
        <module name="GenericWhitespace"/>

        <module name="WhitespaceAround">
            <!-- Checks that various tokens are surrounded by whitespace.
                 This includes most binary operators and keywords followed
                 by regular or curly braces.
            -->
            <property name="tokens" value="ASSIGN, BAND, BAND_ASSIGN, BOR,
        BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN,
        EQUAL, GE, GT, LAND, LCURLY, LE, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE,
        LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF, LITERAL_RETURN,
        LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS,
        MINUS_ASSIGN, MOD, MOD_ASSIGN, NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION,
        SL, SLIST, SL_ASSIGN, SR_ASSIGN, STAR, STAR_ASSIGN"/>
            <property name="allowEmptyConstructors" value="true"/>
            <property name="allowEmptyMethods" value="true"/>
            <property name="severity" value="error"/>
        </module>

        <module name="WhitespaceAfter">
            <!-- Checks that commas, semicolons and typecasts are followed by
                 whitespace.
            -->
            <property name="tokens" value="COMMA, SEMI, TYPECAST"/>
            <property name="severity" value="error"/>
        </module>

        <module name="NoWhitespaceAfter">
            <!-- Checks that there is no whitespace after various unary operators.
                 Linebreaks are allowed.
            -->
            <property name="tokens" value="BNOT, DEC, DOT, INC, LNOT, UNARY_MINUS,
        UNARY_PLUS"/>
            <property name="allowLineBreaks" value="true"/>
            <property name="severity" value="error"/>
        </module>

        <module name="NoWhitespaceBefore">
            <!-- Checks that there is no whitespace before various unary operators.
                 Linebreaks are allowed.
            -->
            <property name="tokens" value="SEMI, DOT, POST_DEC, POST_INC"/>
            <property name="allowLineBreaks" value="true"/>
            <property name="severity" value="error"/>
        </module>

        <module name="ParenPad">
            <!-- Checks that there is no whitespace before close parens or after
                 open parens.
            -->
            <property name="severity" value="error"/>
        </module>

    </module>

    <!--
      Optional suppression filter. It is optional because when running with Maven, it should be the
       checkstyle plugin who provides it. It is only used when this file is used in IntelliJ.
      -->

    <module name="SuppressionFilter">
        <property name="file" value="suppressions.xml"/>
        <property name="optional" value="true"/>
    </module>
</module>