1877: Add checkstyle to project (#2042)

* 1877: Add checkstyle to project

Add checkstyle plugin to common.gradle
Add a checkstyle.xml based on google checkstyle xml with ammendments.
Checkstyle errors do not fail the build, everything is marked as a
warning, can be refined over time as per comments in #1877.

Checkstyle can be run with `./gradlew checkstyleMain` - it runs for all
projects.

* 1877: Updated to work with Java 8

Wound back checkstyle version to 9.3
Last good version to work out of the box with java 8
Re-copied the google checkstyle config from that version too
Updated the links in the checkstyle config to the right docs url.
Rebuilt with Java 8 & 17 to test.

* 1877: Reduce checks to limit output

* Ignore some modules that produce a lot of warnings.
* Increase line length to 150 so we only get the worst offenders
* Reduces output by ~70% (counting main.html sizes, about 4M)

* Reduced checkstyle output

* Don't run checkstyle on jme3-networking and jme3-vr
* These two make up about 1M of reporting
* Fixed ref to checkstyle-suppressions and added a template file
* Removed suppressionXPathFilter
* Disabled a couple more checks.
* Output is down to ~ 2.2M

* 1877: Further refinement of output

* Only process /com/jme3/renderer sources
* Rolled back jme3-network/vr exclusion (still not processed though)
* Added modules back into checkstyle config
* Now gives 38 errors from 11 files within com/jme3/renderer package
* BeforeExecutionExclusionFileFilter wasn't playing nicely

* 1877: Fixed package filter

* Realised I made a mistake on the package filter
* was only pulling java classes directly under com/jme/renderer/
* Ammded to include all java classes in that package
* Opened up to 200Kb of errors over 4 projects

* 1877: Fixed some style rules

* Made style changes suggested in the PR comments

common.gradle

@@ -7,6 +7,8 @@ apply plugin: 'groovy'
 apply plugin: 'maven-publish'
 apply plugin: 'signing'
 apply plugin: 'eclipse'
+apply plugin: 'checkstyle'
+
 eclipse.jdt.file.withProperties { props ->
     props.setProperty "org.eclipse.jdt.core.circularClasspath", "warning"
 }
@@ -200,3 +202,24 @@ signing {
 tasks.withType(Sign) {
     onlyIf { gradle.rootProject.hasProperty('signingKey') }
 }
+
+checkstyle {
+    toolVersion '9.3'
+    configFile file("${gradle.rootProject.rootDir}/config/checkstyle/checkstyle.xml")
+}
+
+checkstyleMain {
+    source ='src/main/java'
+}
+
+checkstyleTest {
+    source ='src/test/java'
+}
+
+tasks.withType(Checkstyle) {
+    reports {
+        xml.enabled false
+        html.enabled true
+    }
+    include("**/com/jme3/renderer/**/*.java")
+}

config/checkstyle/checkstyle-suppressions.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0"?>
+<!DOCTYPE suppressions PUBLIC "-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN" "https://checkstyle.org/dtds/suppressions_1_2.dtd">
+
+<suppressions>
+    <!-- https://checkstyle.org/filters/suppressionfilter.html -->
+</suppressions>

config/checkstyle/checkstyle.xml

@@ -0,0 +1,361 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN" "https://checkstyle.org/dtds/configuration_1_3.dtd">
+
+<!--
+    Checkstyle configuration that checks the Google coding conventions from Google Java Style
+    that can be found at https://google.github.io/styleguide/javaguide.html. 
+
+    Based on google_checks.xml found in the checkstyle repository:
+    https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml
+
+    Adapted for changes by the jMonkeyEngine contribution guidelines document.
+ -->
+
+<module name="Checker">
+    <property name="charset" value="UTF-8" />
+
+    <property name="severity" value="warning" />
+
+    <property name="fileExtensions" value="java, properties, xml" />
+    <!-- Excludes all 'module-info.java' files              -->
+    <!-- See https://checkstyle.org/filefilters/index.html -->
+    <module name="BeforeExecutionExclusionFileFilter">
+        <property name="fileNamePattern" value="module\-info\.java$" />
+    </module>
+
+    <!-- https://checkstyle.org/filters/suppressionfilter.html -->
+    <module name="SuppressionFilter">
+        <property name="file" value="config/checkstyle/checkstyle-suppressions.xml"/>
+        <property name="optional" value="true" />
+    </module>
+
+    <!-- Checks for whitespace                               -->
+    <!-- See https://checkstyle.org/checks/whitespace/index.html -->
+    <module name="FileTabCharacter">
+        <property name="eachLine" value="false" />
+    </module>
+
+    <module name="LineLength">
+        <property name="fileExtensions" value="java" />
+        <property name="max" value="110" />
+        <property name="ignorePattern"
+            value="^package.*|^import.*|a href|href|http://|https://|ftp://" />
+    </module>
+
+    <module name="TreeWalker">
+        <module name="OuterTypeFilename" />
+        <module name="IllegalTokenText">
+            <property name="tokens" value="STRING_LITERAL, CHAR_LITERAL" />
+            <property name="format"
+                value="\\u00(09|0(a|A)|0(c|C)|0(d|D)|22|27|5(C|c))|\\(0(10|11|12|14|15|42|47)|134)" />
+            <property name="message"
+                value="Consider using special escape sequence instead of octal value or Unicode escaped value." />
+        </module>
+        <module name="AvoidEscapedUnicodeCharacters">
+            <property name="allowEscapesForControlCharacters" value="true" />
+            <property name="allowByTailComment" value="true" />
+            <property name="allowNonPrintableEscapes" value="true" />
+        </module>
+        <module name="AvoidStarImport"/>
+        <module name="OneTopLevelClass" />
+        <module name="NoLineWrap">
+            <property name="tokens" value="PACKAGE_DEF, IMPORT, STATIC_IMPORT" />
+        </module>
+        <module name="EmptyBlock">
+            <property name="option" value="TEXT" />
+            <property name="tokens"
+                value="LITERAL_TRY, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_SWITCH" />
+        </module>
+        <module name="NeedBraces">
+            <property name="tokens"
+                value="LITERAL_DO, LITERAL_ELSE, LITERAL_FOR, LITERAL_IF, LITERAL_WHILE" />
+        </module>
+        <module name="LeftCurly">
+            <property name="tokens"
+                value="ANNOTATION_DEF, CLASS_DEF, CTOR_DEF, ENUM_CONSTANT_DEF, ENUM_DEF,
+                    INTERFACE_DEF, LAMBDA, LITERAL_CASE, LITERAL_CATCH, LITERAL_DEFAULT,
+                    LITERAL_DO, LITERAL_ELSE, LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF,
+                    LITERAL_SWITCH, LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, METHOD_DEF,
+                    OBJBLOCK, STATIC_INIT, RECORD_DEF, COMPACT_CTOR_DEF" />
+        </module>
+        <module name="RightCurly">
+            <property name="id" value="RightCurlySame" />
+            <property name="tokens"
+                value="LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE,
+                    LITERAL_DO" />
+        </module>
+        <module name="RightCurly">
+            <property name="id" value="RightCurlyAlone" />
+            <property name="option" value="alone" />
+            <property name="tokens"
+                value="CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, STATIC_INIT,
+                    INSTANCE_INIT, ANNOTATION_DEF, ENUM_DEF, INTERFACE_DEF, RECORD_DEF,
+                    COMPACT_CTOR_DEF" />
+        </module>
+        <module name="SuppressionXpathSingleFilter">
+            <!-- suppresion is required till https://github.com/checkstyle/checkstyle/issues/7541 -->
+            <property name="id" value="RightCurlyAlone" />
+            <property name="query"
+                value="//RCURLY[parent::SLIST[count(./*)=1]
+                                     or preceding-sibling::*[last()][self::LCURLY]]" />
+        </module>
+        <module name="WhitespaceAfter">
+            <property name="tokens"
+                value="COMMA, SEMI, TYPECAST, LITERAL_IF, LITERAL_ELSE,
+                    LITERAL_WHILE, LITERAL_DO, LITERAL_FOR, DO_WHILE" />
+        </module>
+        <module name="WhitespaceAround">
+            <property name="allowEmptyConstructors" value="true" />
+            <property name="allowEmptyLambdas" value="true" />
+            <property name="allowEmptyMethods" value="true" />
+            <property name="allowEmptyTypes" value="true" />
+            <property name="allowEmptyLoops" value="true" />
+            <property name="ignoreEnhancedForColon" value="false" />
+            <property name="tokens"
+                value="ASSIGN, BAND, BAND_ASSIGN, BOR, BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR,
+                    BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN, DO_WHILE, EQUAL, GE, GT, LAMBDA, LAND,
+                    LCURLY, LE, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE, LITERAL_FINALLY,
+                    LITERAL_FOR, LITERAL_IF, LITERAL_RETURN, LITERAL_SWITCH, LITERAL_SYNCHRONIZED,
+                    LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS, MINUS_ASSIGN, MOD, MOD_ASSIGN,
+                    NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION, RCURLY, SL, SLIST, SL_ASSIGN, SR,
+                    SR_ASSIGN, STAR, STAR_ASSIGN, LITERAL_ASSERT, TYPE_EXTENSION_AND" />
+            <message key="ws.notFollowed"
+                value="WhitespaceAround: ''{0}'' is not followed by whitespace. Empty blocks may only be represented as '{}' when not part of a multi-block statement (4.1.3)" />
+            <message key="ws.notPreceded"
+                value="WhitespaceAround: ''{0}'' is not preceded with whitespace." />
+        </module>
+        <module name="OneStatementPerLine" />
+        <module name="MultipleVariableDeclarations" />
+        <module name="ArrayTypeStyle" />
+        <module name="MissingSwitchDefault" />
+        <module name="FallThrough" />
+        <module name="UpperEll" />
+        <module name="ModifierOrder" />
+        <module name="EmptyLineSeparator">
+            <property name="tokens"
+                value="IMPORT, STATIC_IMPORT, CLASS_DEF, INTERFACE_DEF, ENUM_DEF,
+                    STATIC_INIT, INSTANCE_INIT, METHOD_DEF, CTOR_DEF, VARIABLE_DEF, RECORD_DEF,
+                    COMPACT_CTOR_DEF" />
+            <property name="allowNoEmptyLineBetweenFields" value="true" />
+        </module>
+        <module name="SeparatorWrap">
+            <property name="id" value="SeparatorWrapDot" />
+            <property name="tokens" value="DOT" />
+            <property name="option" value="nl" />
+        </module>
+        <module name="SeparatorWrap">
+            <property name="id" value="SeparatorWrapComma" />
+            <property name="tokens" value="COMMA" />
+            <property name="option" value="EOL" />
+        </module>
+        <module name="SeparatorWrap">
+            <!-- ELLIPSIS is EOL until https://github.com/google/styleguide/issues/259 -->
+            <property name="id" value="SeparatorWrapEllipsis" />
+            <property name="tokens" value="ELLIPSIS" />
+            <property name="option" value="EOL" />
+        </module>
+        <module name="SeparatorWrap">
+            <!-- ARRAY_DECLARATOR is EOL until https://github.com/google/styleguide/issues/258 -->
+            <property name="id" value="SeparatorWrapArrayDeclarator" />
+            <property name="tokens" value="ARRAY_DECLARATOR" />
+            <property name="option" value="EOL" />
+        </module>
+        <module name="SeparatorWrap">
+            <property name="id" value="SeparatorWrapMethodRef" />
+            <property name="tokens" value="METHOD_REF" />
+            <property name="option" value="nl" />
+        </module>
+        <module name="PackageName">
+            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$" />
+            <message key="name.invalidPattern"
+                value="Package name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="TypeName">
+            <property name="tokens"
+                value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF,
+                    ANNOTATION_DEF, RECORD_DEF" />
+            <message key="name.invalidPattern"
+                value="Type name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="MemberName">
+            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$" />
+            <message key="name.invalidPattern"
+                value="Member name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="ParameterName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$" />
+            <message key="name.invalidPattern"
+                value="Parameter name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="LambdaParameterName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$" />
+            <message key="name.invalidPattern"
+                value="Lambda parameter name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="CatchParameterName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$" />
+            <message key="name.invalidPattern"
+                value="Catch parameter name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="LocalVariableName">
+            <property name="format" value="^[a-z]([a-zA-Z0-9]*)?$" />
+            <message key="name.invalidPattern"
+                value="Local variable name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="PatternVariableName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$" />
+            <message key="name.invalidPattern"
+                value="Pattern variable name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="ClassTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)" />
+            <message key="name.invalidPattern"
+                value="Class type name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="RecordComponentName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$" />
+            <message key="name.invalidPattern"
+                value="Record component name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="RecordTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)" />
+            <message key="name.invalidPattern"
+                value="Record type name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="MethodTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)" />
+            <message key="name.invalidPattern"
+                value="Method type name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="InterfaceTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)" />
+            <message key="name.invalidPattern"
+                value="Interface type name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="NoFinalizer" />
+        <module name="GenericWhitespace">
+            <message key="ws.followed"
+                value="GenericWhitespace ''{0}'' is followed by whitespace." />
+            <message key="ws.preceded"
+                value="GenericWhitespace ''{0}'' is preceded with whitespace." />
+            <message key="ws.illegalFollow"
+                value="GenericWhitespace ''{0}'' should followed by whitespace." />
+            <message key="ws.notPreceded"
+                value="GenericWhitespace ''{0}'' is not preceded with whitespace." />
+        </module>
+        <module name="Indentation">
+            <property name="basicOffset" value="4" />
+            <property name="braceAdjustment" value="4" />
+            <property name="caseIndent" value="4" />
+            <property name="throwsIndent" value="4" />
+            <property name="lineWrappingIndentation" value="8" />
+            <property name="arrayInitIndent" value="4" />
+        </module>
+        <module name="AbbreviationAsWordInName">
+            <property name="ignoreFinal" value="false" />
+            <property name="allowedAbbreviationLength" value="1" />
+            <property name="tokens"
+                value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, ANNOTATION_DEF, ANNOTATION_FIELD_DEF,
+                    PARAMETER_DEF, VARIABLE_DEF, METHOD_DEF, PATTERN_VARIABLE_DEF, RECORD_DEF,
+                    RECORD_COMPONENT_DEF" />
+        </module>
+        <module name="NoWhitespaceBeforeCaseDefaultColon" />
+        <module name="VariableDeclarationUsageDistance" />
+        <module name="CustomImportOrder">
+            <property name="sortImportsInGroupAlphabetically" value="true" />
+            <property name="separateLineBetweenGroups" value="true" />
+            <property name="customImportOrderRules" value="STATIC###THIRD_PARTY_PACKAGE" />
+            <property name="tokens" value="IMPORT, STATIC_IMPORT, PACKAGE_DEF" />
+        </module>
+        <module name="MethodParamPad">
+            <property name="tokens"
+                value="CTOR_DEF, LITERAL_NEW, METHOD_CALL, METHOD_DEF,
+                    SUPER_CTOR_CALL, ENUM_CONSTANT_DEF, RECORD_DEF" />
+        </module>
+        <module name="NoWhitespaceBefore">
+            <property name="tokens"
+                value="COMMA, SEMI, POST_INC, POST_DEC, DOT,
+                    LABELED_STAT, METHOD_REF" />
+            <property name="allowLineBreaks" value="true" />
+        </module>
+        <module name="ParenPad">
+            <property name="tokens"
+                value="ANNOTATION, ANNOTATION_FIELD_DEF, CTOR_CALL, CTOR_DEF, DOT, ENUM_CONSTANT_DEF,
+                    EXPR, LITERAL_CATCH, LITERAL_DO, LITERAL_FOR, LITERAL_IF, LITERAL_NEW,
+                    LITERAL_SWITCH, LITERAL_SYNCHRONIZED, LITERAL_WHILE, METHOD_CALL,
+                    METHOD_DEF, QUESTION, RESOURCE_SPECIFICATION, SUPER_CTOR_CALL, LAMBDA,
+                    RECORD_DEF" />
+        </module>
+        <module name="OperatorWrap">
+            <property name="option" value="NL" />
+            <property name="tokens"
+                value="BAND, BOR, BSR, BXOR, DIV, EQUAL, GE, GT, LAND, LE, LITERAL_INSTANCEOF, LOR,
+                    LT, MINUS, MOD, NOT_EQUAL, PLUS, QUESTION, SL, SR, STAR, METHOD_REF,
+                    TYPE_EXTENSION_AND " />
+        </module>
+        <module name="AnnotationLocation">
+            <property name="id" value="AnnotationLocationMostCases" />
+            <property name="tokens"
+                value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF,
+                      RECORD_DEF, COMPACT_CTOR_DEF" />
+        </module>
+        <module name="AnnotationLocation">
+            <property name="id" value="AnnotationLocationVariables" />
+            <property name="tokens" value="VARIABLE_DEF" />
+            <property name="allowSamelineMultipleAnnotations" value="true" />
+        </module>
+        <module name="NonEmptyAtclauseDescription" />
+
+        <!--
+
+        Commented out javadoc checks, these produce a lot (4k in jme3-core) of warnings so for now, might
+        be too noisy
+
+        <module name="InvalidJavadocPosition" />
+        <module name="JavadocTagContinuationIndentation" />
+        <module name="SummaryJavadoc">
+            <property name="forbiddenSummaryFragments"
+                value="^@return the *|^This method returns |^A [{]@code [a-zA-Z0-9]+[}]( is a )" />
+        </module>
+        <module name="JavadocParagraph" />
+        <module name="RequireEmptyLineBeforeBlockTagGroup" />
+        <module name="AtclauseOrder">
+            <property name="tagOrder" value="@param, @return, @throws, @deprecated" />
+            <property name="target"
+                value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF, VARIABLE_DEF" />
+        </module>
+        <module name="JavadocMethod">
+            <property name="accessModifiers" value="public" />
+            <property name="allowMissingParamTags" value="true" />
+            <property name="allowMissingReturnTag" value="true" />
+            <property name="allowedAnnotations" value="Override, Test" />
+            <property name="tokens"
+                value="METHOD_DEF, CTOR_DEF, ANNOTATION_FIELD_DEF, COMPACT_CTOR_DEF" />
+        </module>
+        <module name="MissingJavadocMethod">
+            <property name="scope" value="public" />
+            <property name="minLineCount" value="2" />
+            <property name="allowedAnnotations" value="Override, Test" />
+            <property name="tokens"
+                value="METHOD_DEF, CTOR_DEF, ANNOTATION_FIELD_DEF,
+                                   COMPACT_CTOR_DEF" />
+        </module>
+        <module name="MissingJavadocType">
+            <property name="scope" value="protected" />
+            <property name="tokens"
+                value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF,
+                      RECORD_DEF, ANNOTATION_DEF" />
+            <property name="excludeScope" value="nothing" />
+        </module>
+        <module name="MethodName">
+            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9_]*$" />
+            <message key="name.invalidPattern"
+                value="Method name ''{0}'' must match pattern ''{1}''." />
+        </module>
+        <module name="SingleLineJavadoc" />
+    -->
+        <module name="EmptyCatchBlock">
+            <property name="exceptionVariableName" value="expected" />
+        </module>
+    </module>
+</module>

jme3-vr/build.gradle

@@ -27,3 +27,4 @@ javadoc {
         options.addStringOption('Xdoclint:none', '-quiet')
     }
 }
+