scalastyle-config.xml

<?xml version="1.0"?>
<scalastyle>
    <!--
      http://www.scalastyle.org/rules-1.0.0.html

      The ID values are used for suppressing a check in limited situations, using either a block level comment pair:

        // scalastyle:off ID_GOES_HERE
        ... code ...
        // scalastyle:on ID_GOES_HERE

      or a single line suppression (at the end of the line):

        ... code ... // scalastyle:ignore ID_GOES_HERE
    -->
    <name>Scalastyle standard configuration</name>
    <check level="error" enabled="true" class="org.scalastyle.file.FileLengthChecker">
        <!--
          Check the number of lines in a file.
          ID: file.size.limit
          Justification: Files which are too long can be hard to read and understand.
        -->
        <parameters>
            <parameter name="maxFileLength"><![CDATA[800]]></parameter>
        </parameters>
    </check>
    <check level="warning" enabled="true" class="org.scalastyle.file.FileLineLengthChecker">
        <!--
          Check the number of characters in a line.
          ID: line.size.limit
          Justification: Lines that are too long can be hard to read and horizontal scrolling is annoying.
        -->
        <parameters>
            <parameter name="ignoreImports"><![CDATA[false]]></parameter>
            <parameter name="maxLineLength"><![CDATA[160]]></parameter>
            <parameter name="tabSize"><![CDATA[2]]></parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.file.FileTabChecker">
        <!--
          Check that there are no tabs in a file.
          ID: line.contains.tab
          Justification: Some say that tabs are evil.
        -->
    </check>
    <check level="warning" enabled="false" class="org.scalastyle.file.HeaderMatchesChecker">
        <!--
          Check the first lines of each file matches the text
          ID: header.matches
          Justification: A lot of projects require a header with a copyright notice, or they require a license in each file.
            This check does a simple text comparison between the header and the first lines of the file. You can have
            multiple lines, but make sure you surround the text with a CDATA section. You can also specify a regular
            expression, as long as you set the regex parameter to true.
        -->
        <parameters>
            <parameter name="header"><![CDATA[// No copyright required.]]></parameter>
            <parameter name="regex">false</parameter>
        </parameters>
    </check>
    <check level="warning" enabled="false" class="org.scalastyle.file.IndentationChecker">
        <!--
          Checks that lines are indented by a multiple of the tab size.
          ID: indentation
          Justification: Code that is not indented consistently can be hard to read.
        -->
        <parameters>
            <parameter name="classParamIndentSize">2</parameter>
            <parameter name="methodParamIndentSize">2</parameter>
            <parameter name="tabSize">2</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.file.NewLineAtEofChecker">
        <!--
          Checks that a file ends with a newline character.
          ID: newline.at.eof
          Justification: Some version control systems don't cope well with files which don't end with a newline character.
        -->
    </check>
    <check level="error" enabled="false" class="org.scalastyle.file.NoNewLineAtEofChecker">
        <!--
          Checks that a file does not end with a newline character.
          ID: no.newline.at.eof
          Justification: Because Mirco Dotta wanted it.
          MUST BE DISABLED.
        -->
    </check>
    <check level="error" enable="true" class="org.scalastyle.file.RegexChecker">
        <!--
          Checks that a regular expression cannot be matched; if found reports this.
          ID: regex
          Justification: Some checks can be carried out with a regular expression.
        -->
        <parameters>
            <parameter name="regex"><![CDATA[(?m)^\s*$(\r|)\n^\s*$(\r|)\n]]></parameter>
            <parameter name="line">false</parameter>
        </parameters>
        <customMessage>No double blank lines</customMessage>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.file.WhitespaceEndOfLineChecker">
        <!--
          Check that there is no trailing whitespace at the end of lines.
          ID: whitespace.end.of.line
          Justification: Whitespace at the end of a line can cause problems when diffing between files or between versions.
        -->
        <parameters>
            <parameter name="ignoreWhitespaceLines">false</parameter>
        </parameters>
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.BlockImportChecker">
        <!--
          Checks that block imports are not used.
          ID: block.import
          Justification: Block imports (e.g. `import a.{b, c}`) can lead to annoying merge errors in large code bases that
            are maintained by lot of developers. This rule ensures that only single imports are used in order to minimize
            merge errors in import declarations.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.ClassNamesChecker">
        <!--
          Check that class names match a regular expression.
          ID: class.name
          Justification: The Scala style guide recommends that class names conform to certain standards.
        -->
        <parameters>
            <parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.ClassTypeParameterChecker">
        <!--
          Checks that type parameter to a class matches a regular expression.
          ID: class.type.parameter.name
          Justification: Scala generic type names are generally single upper case letters. This check checks for classes and
            traits. Note that this check only checks the innermost type parameter, to allow for `List[T]`.
        -->
        <parameters>
            <parameter name="regex"><![CDATA[^[A-Z_]$]]></parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.CovariantEqualsChecker">
        <!--
          Check that classes and objects do not define equals without overriding `equals(java.lang.Object)`.
          ID: covariant.equals
          Justification: Mistakenly defining a covariant `equals()` method without overriding method
            `equals(java.lang.Object)` can produce unexpected runtime behaviour.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.CyclomaticComplexityChecker">
        <!--
          Checks that the cyclomatic complexity of a method does exceed a value.
          ID: cyclomatic.complexity
          Justification: If the code is too complex, then this can make code hard to read.
        -->
        <parameters>
            <parameter name="countCases">true</parameter>
            <parameter name="maximum">10</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.DeprecatedJavaChecker">
        <!--
          Checks that Java `@Deprecated` is not used, Scala `@deprecated` should be used instead.
          ID: deprecated.java
          Justification: You should be using the Scala `@deprecated` instead.
        -->
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.DisallowSpaceAfterTokenChecker">
        <!--
          Disallow space after certain token(s).
          ID: disallow.space.after.token
          Justification: Correct formatting can help readability.
        -->
        <parameters>
            <parameter name="tokens">LPAREN</parameter>
        </parameters>
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.DisallowSpaceBeforeTokenChecker">
        <!--
          Disallow space before certain token(s).
          ID: disallow.space.before.token
          Justification: Correct formatting can help readability.
        -->
        <parameters>
            <parameter name="tokens">COLON, COMMA, RPAREN</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.EmptyClassChecker">
        <!--
          If a class/trait has no members, the braces are unnecessary.
          ID: empty.class
          Justification: If a class / trait has no members, then braces are unnecessary, and can be removed.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.EmptyInterpolatedStringChecker">
        <!--
          The interpolation for this string literal is not necessary.
          ID: empty.interpolated.strings
          Justification: Empty interpolated strings are harder to read and not necessary.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.EnsureSingleSpaceAfterTokenChecker">
        <!--
          Ensure single space after certain token(s).
          ID: ensure.single.space.after.token
          Justification: Correct formatting can help readability.
        -->
        <parameters>
            <parameter name="tokens">COLON, COMMA, IF</parameter>
        </parameters>
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.EnsureSingleSpaceBeforeTokenChecker">
        <!--
          Ensure single space before certain token(s).
          ID: ensure.single.space.before.token
          Justification: Correct formatting can help readability.
        -->
        <parameters>
            <parameter name="tokens"></parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.EqualsHashCodeChecker">
        <!--
          Check that if a class implements either `equals` or `hashCode`, it should implement the other.
          ID: equals.hash.code
          Justification: Defining either `equals` or `hashCode` in a class without defining the other is a known source of
            bugs. Usually, when you define one, you should also define the other.
        -->
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.FieldNamesChecker">
        <!--
          Check that field names match a regular expression.
          ID: field.name
          Justification: A consistent naming convention for field names can make code easier to read and understand:
            - Constants in an object must be in `PascalCase` a.k.a `TitleCase`.
            - Fields in a class must be in `camelCase`.
        -->
        <parameters>
            <parameter name="objectFieldRegex"><![CDATA[^[A-Z][A-Za-z0-9]*$]]></parameter>
            <parameter name="regex"><![CDATA[^[a-z][A-Za-z]*$]]></parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.ForBraceChecker">
        <!--
          Checks that braces are used in for comprehensions.
          ID: for.brace
          Justification: Usage of braces (rather than parentheses) within a `for` comprehension means that you don't have to
            specify a semi-colon at the end of every line:

            ```
            for {      // braces
              t <- List(1,2,3)
              if (i % 2 == 0)
            } yield t
            ```

            is preferred to:

            ```
            for (      // parentheses
              t <- List(1,2,3);
              if (i % 2 == 0)
            ) yield t
            ```

            To fix it, replace the `()` with `{}`. And then remove the `;` at the end of the lines.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.IfBraceChecker">
        <!--
          Checks that `if` statements have braces.
          ID: if.brace
          Justification: Some people find `if` clauses with braces easier to read.
        -->
        <parameters>
            <parameter name="singleLineAllowed">true</parameter>
            <parameter name="doubleLineAllowed">false</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.IllegalImportsChecker">
        <!--
          Check that a class does not import certain classes.
          ID: illegal.imports
          Justification: Use of some classes can be discouraged for a project. For instance, use of `sun._` is generally
            discouraged because they are internal to the JDK and can be changed.
        -->
        <parameters>
            <parameter name="illegalImports"><![CDATA[sun._,java.awt._]]></parameter>
        </parameters>
    </check>
    <check level="info" enabled="true" class="org.scalastyle.scalariform.ImportGroupingChecker">
        <!--
          Checks that imports are grouped together, not throughout the file.
          ID: import.grouping
          Justification: If imports are spread throughout the file, knowing what is in scope at any one place can be
            difficult to work out.
        -->
    </check>
    <check level="info" enabled="false" class="org.scalastyle.scalariform.ImportOrderChecker">
        <!--
          Checks that imports are grouped and ordered according to the style configuration.
          ID: import.ordering
          Justification: Consistent import ordering improves code readability and reduces unrelated changes in patches.
          NOTE: This check is now disabled, to minimize developer pain due to IntelliJ's inconsistent sorting; for details
                see: https://zendesk.atlassian.net/browse/BOLT-1768
        -->
        <parameters>
            <parameter name="groups">java,others,scala</parameter>
            <parameter name="group.java">javax?\..+</parameter>
            <parameter name="group.others">^(?!scala\.|javax?\.).+</parameter>
            <parameter name="group.scala">scala\..+</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.LowercasePatternMatchChecker">
        <!--
          Checks that a case statement pattern match is not lower case, as this can cause confusion.
          ID: lowercase.pattern.match
          Justification: A lower case pattern match clause with no other tokens is the same as `_`; this is not true for
            patterns which start with an upper case letter. This can cause confusion, and may not be what was intended:

            ```
            val foo = "foo"
            val Bar = "bar"
            "bar" match { case Bar => "we got bar" }   // result = "we got bar"
            "bar" match { case foo => "we got foo" }   // result = "we got foo"
            "bar" match { case `foo` => "we got foo" } // result = MatchError
            ```

            This checker raises a warning with the second match. To fix it, use an identifier which starts with an upper case
            letter (best), use `case _` or, if you wish to refer to the value, add a type `: Any`

            ```
            val lc = "lc"
            "something" match { case lc: Any => "lc" } // result = "lc"
            "something" match { case _ => "lc" } // result = "lc"
            ```
        -->
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.MagicNumberChecker">
        <!--
          Checks for use of magic numbers.
          ID: magic.number
          Justification: Replacing a magic number with a named constant can make code easier to read and understand, and can
            avoid some subtle bugs.

            A simple assignment to a val is not considered to be a magic number, for example:

            ```
            val foo = 4
            ```

            is not a magic number, but

            ```
            var foo = 4
            ```

            is considered to be a magic number.
        -->
        <parameters>
            <parameter name="ignore">-1,0,1,2,3</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.MethodArgumentNamesChecker">
        <!--
          Check that method argument names match a regular expression.
          ID: method.argument.name
          Justification: The Scala style guide recommends that method argument names conform to certain standards.
        -->
        <parameters>
            <parameter name="regex"><![CDATA[^[a-z][A-Za-z0-9]*$]]></parameter>
            <parameter name="ignoreRegex">^$</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.MethodLengthChecker">
        <!--
          Checks that methods do not exceed a maximum length.
          ID: method.length
          Justification: Long methods can be hard to read and understand.
        -->
        <parameters>
            <parameter name="ignoreComments">true</parameter>
            <parameter name="maxLength">50</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.MethodNamesChecker">
        <!--
          Check that method names match a regular expression.
          ID: method.name
          Justification: The Scala style guide recommends that method names conform to certain standards. If the methods are
            overriding another method, and the overridden method cannot be changed, then use the `ignoreOverride` parameter.
        -->
        <parameters>
            <!--
              As well as the standard `pascalCase` method names, this regex allows for:
              - operator methods named `*` and `?` (used with Slick shaped types).
              - pascalCase methods with a `_=` suffix for setters in Finagle (for well-known headers in a message).
              - backtick-escaped names that would otherwise cause a compiler error; usually in case classes for JSON-parsing
                compatibility. May contain dashes and underscores.
            -->
            <parameter name="ignoreOverride">false</parameter>
            <parameter name="ignoreRegex"><![CDATA[^.*$]]></parameter>
            <parameter name="regex"><![CDATA[^(\*|\?|([a-z][A-Za-z0-9]*(_=)?)|(`[a-z][_A-Za-z0-9\-]*?`))$]]></parameter>
        </parameters>
    </check>
    <check level="info" enabled="true" class="org.scalastyle.scalariform.MultipleStringLiteralsChecker">
        <!--
          Checks that a string literal does not appear multiple times.
          ID: multiple.string.literals
          Justification: Code duplication makes maintenance more difficult, so it can be better to replace the multiple
            occurrences with a constant.
        -->
        <parameters>
            <parameter name="allowed">5</parameter>
            <!--
              Workaround for false positive due to string interpolation: make second quote conditional; see
              https://github.com/scalastyle/scalastyle/issues/100#issuecomment-87434823
            -->
            <parameter name="ignoreRegex"><![CDATA[^""?$]]></parameter>
        </parameters>
    </check>
    <check level="warning" enabled="false" class="org.scalastyle.scalariform.NamedArgumentChecker">
        <!--
          Checks that argument literals are named.
          ID: named.argument
          Justification: Nameless literals make code harder to understand (consider `updateEntity(1, true)` and
            `updateEntity(id = 1, enabled = true)`).
        -->
        <parameters>
            <parameter name="checkString">true</parameter>
            <parameter name="ignoreMethod">^set.+$</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.NoCloneChecker">
        <!--
          Check that classes and objects do not define the `clone()` method.
          ID: no.clone
          Justification: The `clone` method is difficult to get right. You can use the `copy` constructor of case classes
          rather than implementing `clone`. For more information on `clone()`, see "Effective Java" by Joshua Bloch.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.NoFinalizeChecker">
        <!--
          Check that classes and objects do not define the `finalize()` method.
          ID: no.finalize
          Justification: `finalize()` is called when the object is garbage collected, and garbage collection is not
          guaranteed to happen. It is therefore unwise to rely on code in the `finalize()` method.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.NoWhitespaceAfterLeftBracketChecker">
        <!--
          No whitespace after left bracket `[`.
          ID: no.whitespace.after.left.bracket
          Justification: If there is whitespace after a left bracket, this can be confusing to the reader.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.NoWhitespaceBeforeLeftBracketChecker">
        <!--
          No whitespace before left bracket `[`.
          ID: no.whitespace.before.left.bracket
          Justification: If there is whitespace before a left bracket, this can be confusing to the reader.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.NoWhitespaceBeforeRightBracketChecker">
        <!--
          No whitespace before right bracket `]`.
          ID: no.whitespace.before.right.bracket
          Justification: If there is whitespace before a right bracket, this can be confusing to the reader.
        -->
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.NonASCIICharacterChecker">
        <!--
          Some editors are unfriendly to non-ASCII characters.
          ID: non.ascii.character.disallowed
          Justification: Scala allows unicode characters as operators and some editors misbehave when they see non-ASCII
            characters.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.NotImplementedErrorUsage">
        <!--
          Checks that the code does not have `???` operators.
          ID: not.implemented.error.usage
          Justification: The `???` operator denotes that an implementation is missing. This rule helps to avoid potential
            runtime errors because of not-implemented code.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.NullChecker">
        <!--
          Check that `null` is not used
          ID: null
          Justification: Scala discourages use of `nulls`, preferring `Option`.
        -->
        <parameters>
            <parameter name="allowNullChecks">true</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.NumberOfMethodsInTypeChecker">
        <!--
          Check that a class / trait / object does not have too many methods.
          ID: number.of.methods
          Justification: If a type declares too many methods, this can be an indication of bad design.
        -->
        <parameters>
            <parameter name="maxMethods">30</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.NumberOfTypesChecker">
        <!--
          Checks that there are not too many types declared in a file.
          ID: number.of.types
          Justification: Too many classes/objects defined in a single file can make the code difficult to understand.
        -->
        <parameters>
            <parameter name="maxTypes">40</parameter>
        </parameters>
    </check>
    <check level="warn" enabled="true" class="org.scalastyle.scalariform.ObjectNamesChecker">
        <!--
          Check that object names match a regular expression.
          ID: object.name
          Justification: The Scala style guide recommends that object names conform to certain standards.
        -->
        <parameters>
            <parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.OverrideJavaChecker">
        <!--
          Checks that Java `@Override` is not used.
          ID: override.java
          Justification: You should be using the Scala `override` keyword instead.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.PackageNamesChecker">
        <!--
          Check that package names match a regular expression
          ID: package.name
          Justification: The Scala style guide recommends that package names conform to certain standards.
        -->
        <parameters>
            <parameter name="regex"><![CDATA[^[a-z][A-Za-z_]*$]]></parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.PackageObjectNamesChecker">
        <!--
          Check that package object names match a regular expression.
          ID: package.object.name
          Justification: The Scala style guide recommends that package object names conform to certain standards.
        -->
        <parameters>
            <parameter name="regex"><![CDATA[^[a-z][A-Za-z_]*$]]></parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.ParameterNumberChecker">
        <!--
          Maximum number of parameters for a method.
          ID: parameter.number
          Justification: A method which has more than a certain number of parameters can be hard to understand. NOTE: This
            number combines implicits and other curried parameters; each parenthesis group is NOT counted separately.
        -->
        <parameters>
            <parameter name="maxParameters">8</parameter>
        </parameters>
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.PatternMatchAlignChecker">
        <!--
          Check that pattern match arrows align.
          ID: pattern.match.align
          Justification: Correct formatting can help readability.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.ProcedureDeclarationChecker">
        <!--
          Use a `: Unit =` for procedure declarations.
          ID: procedure.declaration
          Justification: A procedure style declaration can cause confusion - the developer may have simply forgotten to add
            a `=`, and now their method returns `Unit` rather than the inferred type:

            ```
            def foo() { println("hello"); 5 }
            def foo() = { println("hello"); 5 }
            ```

            This checker raises a warning with the first line. To fix it, use an explicit return type, or add a `=` before
            the body.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.PublicMethodsHaveTypeChecker">
        <!--
          Check that a method has an explicit return type, it is not inferred.
          ID: public.methods.have.type
          Justification: A public method declared on a type is effectively an API declaration. Explicitly declaring a return
            type means that other code which depends on that type won't break unexpectedly.
        -->
        <parameters>
            <parameter name="ignoreOverride">false</parameter>
        </parameters>
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.RedundantIfChecker">
        <!--
          Checks that if expressions are not redundant, i.e. easily replaced by a variant of the condition.
          ID: if.redundant
          Justification: `if` expressions with boolean constants in both branches can be eliminated without affecting
            readability. Prefer simply `cond` to `if (cond) true else false`, and `!cond` to `if (cond) false else true`.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.ReturnChecker">
        <!--
          Check that `return` is not used.
          ID: return
          Justification: Use of `return` is not usually necessary in Scala. In fact, use of `return` can discourage a
            functional style of programming.
        -->
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.ScalaDocChecker">
        <!--
          Checks that the ScalaDoc on documentable members is well-formed.
          ID: scaladoc
          Justification: Scaladoc is generally considered a good thing. Within reason.
        -->
        <parameters>
            <parameter name="ignoreOverride">false</parameter>
            <parameter name="ignoreRegex"><![CDATA[^$]]></parameter>
            <parameter name="ignoreTokenTypes"><![CDATA[^$]]></parameter>
            <parameter name="indentStyle">anydoc</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.SimplifyBooleanExpressionChecker">
        <!--
          Boolean expression can be simplified.
          ID: simplify.boolean.expression
          Justification: A boolean expression which can be simplified can make code easier to read.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.SpaceAfterCommentStartChecker">
        <!--
          Checks for a space after the start of the comment.
          ID: space.after.comment.start
          Justification: To bring consistency with how comments should be formatted, include a
            space immediately after the beginning of the comment.

            ```
            package foobar

            object Foobar {
            /**WRONG
            *
            */
            /** Correct*/
            val d = 2 /*Wrong*/ //Wrong
            /**
            * Correct
            */
            val e = 3/** Correct*/ // Correct
    }
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.SpacesAfterPlusChecker">
        <!--
          Check that the plus sign is followed by a space.
          ID: spaces.after.plus
          Justification: An expression with spaces around `+` can be easier to read.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.SpacesBeforePlusChecker">
        <!--
          Check that the plus sign is preceded by a space.
          ID: spaces.before.plus
          Justification: An expression with spaces around `+` can be easier to read.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.StructuralTypeChecker">
        <!--
          Check that structural types are not used.
          ID: structural.type
          Justification: Structural types in Scala can use reflection - this can have unexpected performance consequences.
            Warning: This check can also wrongly pick up type lamdbas and other such constructs. This checker should be used
            with care. You always have the alternative of the scalac checking for structural types.
        -->
    </check>
    <check level="info" enabled="false" class="org.scalastyle.scalariform.TodoCommentChecker">
        <!--
          Check for use of TODO/FIXME single line comments.
          ID: todo.comment
          Justification: Some projects may consider TODO or FIXME comments in a code bad style. They would rather that you
            fix the problem.
        -->
        <parameters>
            <parameter name="words"><![CDATA[FIXME|HACK|TODO]]></parameter>
        </parameters>
    </check>
    <check level="warning" enabled="false" class="org.scalastyle.scalariform.TokenChecker">
        <!--
          Checks that a regular expression cannot be matched in a token, if found reports this.
          ID: token
          Justification: Some checks can be carried by just the presence of a particular token.
        -->
        <parameters>
            <parameter name="regex"><![CDATA[println]]></parameter>
        </parameters>
        <customMessage>Avoid println</customMessage>
    </check>
    <check level="info" enabled="false" class="org.scalastyle.scalariform.UnderscoreImportChecker">
        <!--
          Avoid wildcard imports
          ID: underscore.import
          Justification: Importing all classes from a package or static members from a class leads to tight coupling between
            packages or classes and might lead to problems when a new version of a library introduces name clashes.
        -->
        <parameters>
            <parameter name="ignoreRegex">collection\.JavaConverters\._|scala\.concurrent\.duration\._</parameter>
        </parameters>
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.UppercaseLChecker">
        <!--
          Checks that if a `long` literal is used, then an uppercase `L` is used.
          ID: uppercase.l
          Justification: A lowercase L (`l`) can look similar to a number 1 with some fonts.
        -->
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.VarFieldChecker">
        <!--
          Checks that classes and objects do not define mutable fields.
          ID: var.field
          Justification: `var` (mutable fields) are deprecated if you're using a strict functional style.
        -->
    </check>
    <check level="error" enabled="true" class="org.scalastyle.scalariform.VarLocalChecker">
        <!--
          Checks that functions do not define mutable variables.
          ID: var.local
          Justification: `var` (mutable local variables) loops are deprecated if you're using a strict functional style.
        -->
    </check>
    <check level="error" enabled="false" class="org.scalastyle.scalariform.WhileChecker">
        <!--
          Checks that while is not used.
          ID: while
          Justification: `while` loops are deprecated if you're using a strict functional style.
        -->
    </check>
</scalastyle>