ruleset.xml

<?xml version="1.0"?>

<ruleset name="PMD HappyCoders Rules (relaxed for binary tree repository)"
  xmlns="http://pmd.sourceforge.net/ruleset/2.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 https://pmd.sourceforge.io/ruleset_2_0_0.xsd">

  <description>PMD ruleset for HappyCoders.eu</description>

  <rule ref="category/java/bestpractices.xml">
    <exclude name="ArrayIsStoredDirectly"/>             <!-- This is usually a good rule as robustness is more important than performance. In Advent of Code, it's the other way round :-) -->
    <exclude name="AvoidReassigningParameters"/>        <!-- IMO, that's OK if you do it right at the beginning of a method, e.g., to trim a String parameter. -->
    <exclude name="LiteralsFirstInComparisons"/>        <!-- IMO, that's OK if you know that the variable is not null. -->
    <exclude name="MethodReturnsInternalArray"/>        <!-- This is usually a good rule as robustness is more important than performance. In Advent of Code, it's the other way round :-) -->
    <exclude name="SystemPrintln"/>                     <!-- While this rule makes sense for most applications, here we just sometimes want to print things. -->
    <exclude name="UseVarargs"/>                        <!-- PMD suggests this where it doesn't make sense, meaning where I always pass in an existing array. -->
  </rule>

  <rule ref="category/java/codestyle.xml">
    <exclude name="AtLeastOneConstructor"/>             <!-- We don't need artificial default constructors. -->
    <exclude name="CallSuperInConstructor"/>            <!-- We don't need to call the super constructor explicitly if it's done implicitly. -->
    <exclude name="CommentDefaultAccessModifier"/>      <!-- We don't comment why we make fields private, protected or public. So why should we comment on default access? -->
    <exclude name="LocalVariableCouldBeFinal"/>         <!-- Using 'final' on local variables (in contrast to fields) has no effect on the compiler; IMO it's noise. -->
    <exclude name="MethodArgumentCouldBeFinal"/>        <!-- Using 'final' on method arguments (in contrast to fields) has no effect on the compiler; IMO it's noise. -->
    <exclude name="OnlyOneReturn"/>                     <!-- IMO not a good rule as it would make some methods more complicated than necessary. -->
    <exclude name="ShortClassName"/>                    <!-- Wouldn't allow class names like "File" -->
    <exclude name="ShortMethodName"/>                   <!-- Wouldn't allow method names like "of". -->
  </rule>

  <rule ref="category/java/codestyle.xml/ShortVariable">
    <properties>
      <property name="minimum" value="2" />             <!-- Default min is 3, but that wouldn't allow a variable name like "id". -->
    </properties>
  </rule>

  <rule ref="category/java/codestyle.xml/TooManyStaticImports">
    <properties>
      <property name="maximumStaticImports" value="10" /><!-- Default is 4, which is too low IMO. -->
    </properties>
  </rule>

  <rule ref="category/java/codestyle.xml/LongVariable">
    <properties>
      <property name="minimum" value="65" />            <!-- Default max is 16, which is not always enough for a descriptive name; allow longer variables. -->
    </properties>
  </rule>

  <rule ref="category/java/design.xml">
    <exclude name="LawOfDemeter"/>                      <!-- That rule also forbids fluent programming style. -->
    <exclude name="UseUtilityClass"/>                   <!-- Usually, this is a good rule; in this project however, I would consider this noise. -->
  </rule>

  <!-- Ignore class length checks for puzzle inputs -->
  <rule ref="category/java/design.xml/ExcessiveClassLength">
    <properties>
      <property name="violationSuppressXPath" value="//ClassOrInterfaceDeclaration['Main*.java']"/>
    </properties>
  </rule>

  <rule ref="category/java/documentation.xml">
    <exclude name="CommentRequired"/>                   <!-- Would require comments on all fields, public methods, and constructors. Good names are a much better documentation. -->
    <exclude name="CommentSize"/>                       <!-- Don't limit the size of comments. -->
  </rule>

  <rule ref="category/java/errorprone.xml">
    <exclude name="AvoidFieldNameMatchingMethodName"/>  <!-- I personally like using the field name also as an accessor name for final fields (like in Java records). -->
    <exclude name="NullAssignment"/>                    <!-- Sometimes, we want to reset a value, e.g. in an array backing a collection, so it can be garbage-collected. -->
    <exclude name="NonSerializableClass"/>              <!-- We don't use serialization. -->
  </rule>

  <!-- Allow a few other literals than the default (-1, 0). -->
  <rule ref="category/java/errorprone.xml/AvoidLiteralsInIfCondition">
    <properties>
      <property name="ignoreMagicNumbers" value="-1,0,1,2" />
    </properties>
  </rule>

  <rule ref="category/java/multithreading.xml">
    <exclude name="UseConcurrentHashMap"/>              <!-- We have no multithreading in Advent of Code. -->
  </rule>

  <rule ref="category/java/performance.xml">
    <exclude name="AvoidInstantiatingObjectsInLoops"/>  <!-- Rule makes sense only sometimes. -->
    <exclude name="InsufficientStringBufferDeclaration"/><!-- I consider this premature optimization. -->
  </rule>

  <rule ref="category/java/security.xml"/>

</ruleset>