Add Checkstyle rules and suppressions

This commit adds Checkstyle rules for EssentialsX, based on those from the adventure library (https://github.com/KyoriPowered/adventure/tree/master/.checkstyle).

It also makes Checkstyle passes mandatory for a GH build to pass.

.checkstyle/checkstyle.xml

@@ -0,0 +1,183 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE module PUBLIC "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+        "https://checkstyle.org/dtds/configuration_1_3.dtd">
+
+<!-- based on https://github.com/KyoriPowered/adventure/blob/master/.checkstyle/checkstyle.xml -->
+
+<module name="Checker">
+    <property name="charset" value="UTF-8"/>
+    <property name="fileExtensions" value="java, properties, xml"/>
+    <property name="severity" value="error"/>
+
+    <!-- https://checkstyle.org/config_filefilters.html#BeforeExecutionExclusionFileFilter -->
+    <module name="BeforeExecutionExclusionFileFilter">
+        <property name="fileNamePattern" value="module\-info\.java$"/>
+    </module>
+
+    <!-- https://checkstyle.org/config_whitespace.html#FileTabCharacter -->
+    <module name="FileTabCharacter">
+        <property name="eachLine" value="true"/>
+    </module>
+
+    <!-- https://checkstyle.org/config_misc.html#NewlineAtEndOfFile -->
+    <module name="NewlineAtEndOfFile"/>
+
+    <!-- https://checkstyle.org/config_filters.html#SuppressionFilter -->
+    <module name="SuppressionFilter">
+        <property name="file" value="${checkstyle.suppressions.file}"/>
+    </module>
+
+    <!-- https://checkstyle.org/config_filters.html#SuppressWithPlainTextCommentFilter -->
+    <module name="SuppressWithPlainTextCommentFilter"/>
+
+    <module name="TreeWalker">
+        <!-- https://checkstyle.org/config_misc.html#ArrayTypeStyle -->
+        <module name="ArrayTypeStyle"/>
+
+        <!-- https://checkstyle.org/config_imports.html#AvoidStarImport -->
+        <module name="AvoidStarImport"/>
+
+        <!-- https://checkstyle.org/config_misc.html#AvoidEscapedUnicodeCharacters -->
+        <module name="AvoidEscapedUnicodeCharacters">
+            <property name="allowByTailComment" value="true"/>
+            <property name="allowEscapesForControlCharacters" value="true"/>
+            <property name="allowNonPrintableEscapes" value="true"/>
+            <property name="severity" value="info"/>
+        </module>
+
+        <!-- https://checkstyle.org/config_misc.html#CommentsIndentation -->
+        <module name="CommentsIndentation"/>
+
+        <!-- https://checkstyle.org/config_whitespace.html#EmptyForInitializerPad -->
+        <module name="EmptyForInitializerPad"/>
+
+        <!-- https://checkstyle.org/config_whitespace.html#EmptyForIteratorPad -->
+        <module name="EmptyForIteratorPad"/>
+
+        <!-- https://checkstyle.org/config_whitespace.html#EmptyLineSeparator -->
+        <module name="EmptyLineSeparator">
+            <property name="allowMultipleEmptyLines" value="false"/>
+            <property name="allowMultipleEmptyLinesInsideClassMembers" value="false"/>
+            <property name="allowNoEmptyLineBetweenFields" value="true"/>
+            <property name="tokens"
+                      value="CLASS_DEF, CTOR_DEF, ENUM_DEF, IMPORT, INSTANCE_INIT, INTERFACE_DEF, METHOD_DEF, STATIC_IMPORT, STATIC_INIT, VARIABLE_DEF"/> <!-- remove PACKAGE_DEF, temporarily remove COMPACT_CTOR_DEF, RECORD_DEF -->
+        </module>
+
+        <!-- https://checkstyle.org/config_coding.html#FallThrough -->
+        <module name="FallThrough">
+            <property name="checkLastCaseGroup" value="true"/>
+        </module>
+
+        <!-- https://checkstyle.org/config_design.html#FinalClass -->
+        <module name="FinalClass"/>
+
+        <!-- https://checkstyle.org/config_coding.html#FinalLocalVariable -->
+        <module name="FinalLocalVariable"/>
+
+        <!-- https://checkstyle.org/config_whitespace.html#GenericWhitespace -->
+        <module name="GenericWhitespace"/>
+
+        <!-- https://checkstyle.org/config_design.html#HideUtilityClassConstructor -->
+        <module name="HideUtilityClassConstructor"/>
+
+        <!-- https://checkstyle.org/config_imports.html#IllegalImport -->
+        <module name="IllegalImport">
+            <property name="illegalPkgs" value="sun, jdk, com.sun"/>
+        </module>
+
+        <!-- https://checkstyle.org/config_coding.html#IllegalTokenText -->
+        <module name="IllegalTokenText">
+            <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."/>
+            <property name="tokens" value="CHAR_LITERAL, STRING_LITERAL"/>
+        </module>
+
+        <!-- https://checkstyle.org/config_misc.html#Indentation -->
+        <module name="Indentation"/>
+
+        <!-- https://checkstyle.org/config_blocks.html#LeftCurly -->
+        <module name="LeftCurly"/>
+
+        <!-- https://checkstyle.org/config_naming.html#MethodName -->
+        <module name="MethodName">
+            <property name="format" value="^[_]?[a-z][a-zA-Z0-9]*$"/>
+        </module>
+
+        <!-- https://checkstyle.org/config_whitespace.html#MethodParamPad -->
+        <module name="MethodParamPad"/>
+
+        <!-- https://checkstyle.org/config_javadoc.html#MissingJavadocMethod -->
+        <module name="MissingJavadocMethod">
+            <property name="allowMissingPropertyJavadoc" value="true"/>
+            <property name="tokens" value="METHOD_DEF, ANNOTATION_FIELD_DEF"/> <!-- remove CTOR_DEF, COMPACT_CTOR_DEF -->
+        </module>
+
+        <!-- https://checkstyle.org/config_javadoc.html#MissingJavadocType -->
+        <module name="MissingJavadocType"/>
+
+        <!-- https://checkstyle.org/config_coding.html#NoFinalizer -->
+        <module name="NoFinalizer"/>
+
+        <!-- https://checkstyle.org/config_whitespace.html#NoLineWrap -->
+        <module name="NoLineWrap"/>
+
+        <!-- https://checkstyle.org/config_whitespace.html#NoWhitespaceAfter -->
+        <module name="NoWhitespaceAfter">
+            <property name="allowLineBreaks" value="false"/>
+        </module>
+
+        <!-- https://checkstyle.org/config_whitespace.html#NoWhitespaceBefore -->
+        <module name="NoWhitespaceBefore">
+            <property name="allowLineBreaks" value="true"/>
+        </module>
+
+        <!-- https://checkstyle.org/config_coding.html#OneStatementPerLine -->
+        <module name="OneStatementPerLine"/>
+
+        <!-- https://checkstyle.org/config_misc.html#OuterTypeFilename -->
+        <module name="OuterTypeFilename"/>
+
+        <!-- https://checkstyle.org/config_imports.html#RedundantImport -->
+        <module name="RedundantImport"/>
+
+        <!-- https://checkstyle.org/config_modifier.html#RedundantModifier -->
+        <module name="RedundantModifier">
+            <property name="tokens"
+                      value="ANNOTATION_FIELD_DEF, CLASS_DEF, CTOR_DEF, ENUM_DEF, INTERFACE_DEF, VARIABLE_DEF"/> <!-- remove METHOD_DEF and RESOURCE -->
+        </module>
+
+        <!-- https://checkstyle.org/config_coding.html#RequireThis -->
+        <module name="RequireThis"/>
+
+        <!-- https://checkstyle.org/config_blocks.html#RightCurly -->
+        <module name="RightCurly">
+            <property name="id" value="RightCurlyAlone"/>
+            <property name="option" value="alone"/>
+            <property name="tokens"
+                      value="ANNOTATION_DEF, CLASS_DEF, CTOR_DEF, ENUM_DEF, INSTANCE_INIT, LITERAL_FOR, LITERAL_WHILE, METHOD_DEF, STATIC_INIT"/>
+        </module>
+        <module name="RightCurly">
+            <property name="id" value="RightCurlySame"/>
+            <property name="option" value="same"/>
+            <property name="tokens"
+                      value="LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE, LITERAL_FINALLY, LITERAL_IF, LITERAL_TRY"/> <!-- add LITERAL_DO -->
+        </module>
+
+        <!-- https://checkstyle.org/config_whitespace.html#SingleSpaceSeparator -->
+        <module name="SingleSpaceSeparator">
+            <property name="validateComments" value="true"/>
+        </module>
+
+        <!-- https://checkstyle.org/config_whitespace.html#TypecastParenPad -->
+        <module name="TypecastParenPad"/>
+
+        <!-- https://checkstyle.org/config_coding.html#UnnecessaryParentheses -->
+        <module name="UnnecessaryParentheses"/>
+
+        <!-- https://checkstyle.org/config_imports.html#UnusedImports -->
+        <module name="UnusedImports"/>
+
+    </module>
+</module>

.checkstyle/suppressions.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE suppressions PUBLIC "-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN" "http://checkstyle.org/dtds/suppressions_1_2.dtd">
+<suppressions>
+    <suppress files=".*[\\/]test[\\/]java[\\/].*" checks="RequireExplicitVisibilityModifier"/>
+    <suppress files="(com[\\/]earth2me[\\/]essentials[\\/]|net[\\/]ess3[\\/])(?:[^\\/]+$|(?!api)[^\\/]+[\\/])" checks="MissingJavadoc(Method|Type)"/>
+</suppressions>

.github/workflows/build.yml

@@ -29,7 +29,7 @@ jobs:
       with:
         java-version: 1.8
     - name: Build with Maven
-      run: mvn package --file pom.xml
+      run: mvn package verify --file pom.xml
     - name: Copy artifacts
       run: mkdir -p ./out/ && cp -t ./out/ **/target/Essentials*.jar
     - uses: actions/upload-artifact@master

.gitignore

@@ -1,11 +1,14 @@
-# IDE files
+# Other IDE files
 *.classpath
 *.project
 *.settings/
-.idea/
+.idea/*
 *.iml
 .DS_Store
 
+# Checkstyle-IDEA config
+!.idea/checkstyle-idea.xml
+
 # Essentials files
 /Essentials/userdata
 /Essentials/config.yml
@@ -16,4 +19,4 @@
 # Build files
 target/
 jars/
-out/
+out/

.idea/checkstyle-idea.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="CheckStyle-IDEA">
+    <option name="configuration">
+      <map>
+        <entry key="active-configuration" value="PROJECT_RELATIVE:$PROJECT_DIR$/.checkstyle/checkstyle.xml:EssentialsX" />
+        <entry key="checkstyle-version" value="8.36.2" />
+        <entry key="copy-libs" value="true" />
+        <entry key="location-0" value="BUNDLED:(bundled):Sun Checks" />
+        <entry key="location-1" value="BUNDLED:(bundled):Google Checks" />
+        <entry key="location-2" value="PROJECT_RELATIVE:$PROJECT_DIR$/.checkstyle/checkstyle.xml:EssentialsX" />
+        <entry key="property-2.checkstyle.suppressions.file" value=".checkstyle/suppressions.xml" />
+        <entry key="scan-before-checkin" value="false" />
+        <entry key="scanscope" value="JavaOnly" />
+        <entry key="suppress-errors" value="false" />
+      </map>
+    </option>
+  </component>
+</project>

pom.xml

@@ -35,10 +35,10 @@
             <id>paper-repo</id>
             <url>https://papermc.io/repo/repository/maven-public/</url>
         </repository>
-		<repository>
+        <repository>
-		    <id>jitpack</id>
+            <id>jitpack</id>
-		    <url>https://jitpack.io</url>
+            <url>https://jitpack.io</url>
-		</repository>
+        </repository>
     </repositories>
 
     <modules>
@@ -188,6 +188,7 @@
                             <value>${full.version}</value>
                         </replacement>
                         <replacement>
+                            <!--suppress UnresolvedMavenProperty -->
                             <token>$${build.number}</token>
                             <value>${full.version}</value>
                         </replacement>
@@ -251,7 +252,24 @@
                     </gitDescribe>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-checkstyle-plugin</artifactId>
+                <version>3.1.1</version>
+                <configuration>
+                    <configLocation>.checkstyle/checkstyle.xml</configLocation>
+                    <suppressionsLocation>.checkstyle/suppressions.xml</suppressionsLocation>
+                </configuration>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>check</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
+
         <resources>
             <resource>
                 <directory>src</directory>
@@ -274,6 +292,7 @@
         <release.version>2.18.1</release.version>
 
         <!-- The plugins' build number -->
+        <!--suppress UnresolvedMavenProperty -->
         <build.version>${git.closest.tag.commit.count}</build.version>
 
         <full.version>${release.version}.${build.version}</full.version>