layout	title
scalastyle	Scalastyle: Implemented Rules

There are 63 rules which are currently implemented:

Checker	Description
org.scalastyle.file.FileLengthChecker	Check the number of lines in a file
org.scalastyle.file.FileLineLengthChecker	Check the number of characters in a line
org.scalastyle.file.FileTabChecker	Check that there are no tabs in a file
org.scalastyle.file.HeaderMatchesChecker	Check the first lines of each file matches the text
org.scalastyle.file.IndentationChecker	Checks that lines are indented by a multiple of the tab size
org.scalastyle.file.NewLineAtEofChecker	Checks that a file ends with a newline character
org.scalastyle.file.NoNewLineAtEofChecker	Checks that a file does not end with a newline character
org.scalastyle.file.RegexChecker	Checks that a regular expression cannot be matched, if found reports this
org.scalastyle.file.WhitespaceEndOfLineChecker	Check that there is no trailing whitespace at the end of lines
org.scalastyle.scalariform.BlockImportChecker	Checks that block imports are not used.
org.scalastyle.scalariform.ClassNamesChecker	Check that class names match a regular expression
org.scalastyle.scalariform.ClassTypeParameterChecker	Checks that type parameter to a class matches a regular expression
org.scalastyle.scalariform.CovariantEqualsChecker	Check that classes and objects do not define equals without overriding equals(java.lang.Object).
org.scalastyle.scalariform.CyclomaticComplexityChecker	Checks that the cyclomatic complexity of a method does exceed a value
org.scalastyle.scalariform.DeprecatedJavaChecker	Checks that Java @Deprecated is not used, Scala @deprecated should be used instead
org.scalastyle.scalariform.DisallowSpaceAfterTokenChecker	Disallow space after certain token(s)
org.scalastyle.scalariform.DisallowSpaceBeforeTokenChecker	Disallow space before certain token(s)
org.scalastyle.scalariform.EmptyClassChecker	If a class/trait has no members, the braces are unnecessary
org.scalastyle.scalariform.EnsureSingleSpaceAfterTokenChecker	Ensure single space after certain token(s)
org.scalastyle.scalariform.EnsureSingleSpaceBeforeTokenChecker	Ensure single space before certain token(s)
org.scalastyle.scalariform.EqualsHashCodeChecker	Check that if a class implements either equals or hashCode, it should implement the other
org.scalastyle.scalariform.FieldNamesChecker	Check that field names match a regular expression
org.scalastyle.scalariform.ForBraceChecker	Checks that braces are used in for comprehensions
org.scalastyle.scalariform.IfBraceChecker	Checks that if statements have braces
org.scalastyle.scalariform.IllegalImportsChecker	Check that a class does not import certain classes
org.scalastyle.scalariform.ImportGroupingChecker	Checks that imports are grouped together, not throughout the file
org.scalastyle.scalariform.ImportOrderChecker	Checks that imports are grouped and ordered according to the style configuration.
org.scalastyle.scalariform.LowercasePatternMatchChecker	Checks that a case statement pattern match is not lower case, as this can cause confusion
org.scalastyle.scalariform.MagicNumberChecker	Checks for use of magic numbers
org.scalastyle.scalariform.MethodLengthChecker	Checks that methods do not exceed a maximum length
org.scalastyle.scalariform.MethodNamesChecker	Check that method names match a regular expression
org.scalastyle.scalariform.MultipleStringLiteralsChecker	Checks that a string literal does not appear multiple times
org.scalastyle.scalariform.NoCloneChecker	Check that classes and objects do not define the clone() method
org.scalastyle.scalariform.NoFinalizeChecker	Check that classes and objects do not define the finalize() method
org.scalastyle.scalariform.NoWhitespaceAfterLeftBracketChecker	No whitespace after left bracket '['
org.scalastyle.scalariform.NoWhitespaceBeforeLeftBracketChecker	No whitespace before left bracket '['
org.scalastyle.scalariform.NonASCIICharacterChecker	Some editors are unfriendly to non ascii characters.
org.scalastyle.scalariform.NotImplementedErrorUsage	Checks that the code does not have ??? operators.
org.scalastyle.scalariform.NullChecker	Check that null is not used
org.scalastyle.scalariform.NumberOfMethodsInTypeChecker	Check that a class / trait / object does not have too many methods
org.scalastyle.scalariform.NumberOfTypesChecker	Checks that there are not too many types declared in a file
org.scalastyle.scalariform.ObjectNamesChecker	Check that object names match a regular expression
org.scalastyle.scalariform.PackageObjectNamesChecker	Check that package object names match a regular expression
org.scalastyle.scalariform.ParameterNumberChecker	Maximum number of parameters for a method
org.scalastyle.scalariform.PatternMatchAlignChecker	Check that pattern match arrows align
org.scalastyle.scalariform.ProcedureDeclarationChecker	Use a : Unit = for procedure declarations
org.scalastyle.scalariform.PublicMethodsHaveTypeChecker	Check that a method has an explicit return type, it is not inferred
org.scalastyle.scalariform.RedundantIfChecker	Checks that if expressions are not redundant, i.e. easily replaced by a variant of the condition
org.scalastyle.scalariform.ReturnChecker	Check that return is not used
org.scalastyle.scalariform.ScalaDocChecker	Checks that the ScalaDoc on documentable members is well-formed
org.scalastyle.scalariform.SimplifyBooleanExpressionChecker	Boolean expression can be simplified
org.scalastyle.scalariform.SpaceAfterCommentStartChecker	Checks a space after the start of the comment.
org.scalastyle.scalariform.SpacesAfterPlusChecker	Check that the plus sign is followed by a space
org.scalastyle.scalariform.SpacesBeforePlusChecker	Check that the plus sign is preceded by a space
org.scalastyle.scalariform.StructuralTypeChecker	Check that structural types are not used.
org.scalastyle.scalariform.TodoCommentChecker	Check for use of TODO/FIXME single line comments
org.scalastyle.scalariform.TokenChecker	Checks that a regular expression cannot be matched in a token, if found reports this
org.scalastyle.scalariform.UnderscoreImportChecker	Avoid wildcard imports
org.scalastyle.scalariform.UppercaseLChecker	Checks that if a long literal is used, then an uppercase L is used
org.scalastyle.scalariform.VarFieldChecker	Checks that classes and objects do not define mutable fields
org.scalastyle.scalariform.VarLocalChecker	Checks that functions do not define mutable variables
org.scalastyle.scalariform.WhileChecker	Checks that while is not used
org.scalastyle.scalariform.XmlLiteralChecker	Check that XML literals are not used

org.scalastyle.file.FileLengthChecker - Check the number of lines in a file

id - file.size.limit
description - Check the number of lines in a file
class - org.scalastyle.file.FileLengthChecker
default level - WarningLevel

Justification

Files which are too long can be hard to read and understand.

Parameters

Parameter	Description	Type	Default Value
maxFileLength	Maximum file length	integer	1500

Example configuration

<check enabled="true" class="org.scalastyle.file.FileLengthChecker" level="warning">
 <parameters>
  <parameter name="maxFileLength">800</parameter>
 </parameters>
</check>

org.scalastyle.file.FileLineLengthChecker - Check the number of characters in a line

id - line.size.limit
description - Check the number of characters in a line
class - org.scalastyle.file.FileLineLengthChecker
default level - WarningLevel

Justification

Lines that are too long can be hard to read and horizontal scrolling is annoying.

Parameters

Parameter	Description	Type	Default Value
maxLineLength	Maximum line length	integer	160
tabSize	Tab size	integer	4
ignoreImports	Ignore import statements	boolean	false

Example configuration

<check enabled="true" class="org.scalastyle.file.FileLineLengthChecker" level="warning">
 <parameters>
  <parameter default="100" type="integer" name="maxLineLength"/>
  <parameter default="2" type="integer" name="tabSize"/>
  <parameter default="true" type="boolean" name="ignoreImports"/>
 </parameters>
</check>

org.scalastyle.file.FileTabChecker - Check that there are no tabs in a file

id - line.contains.tab
description - Check that there are no tabs in a file
class - org.scalastyle.file.FileTabChecker
default level - WarningLevel

Justification

Some say that tabs are evil.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.file.FileTabChecker" level="warning"/>

org.scalastyle.file.HeaderMatchesChecker - Check the first lines of each file matches the text

id - header.matches
description - Check the first lines of each file matches the text
class - org.scalastyle.file.HeaderMatchesChecker
default level - WarningLevel

Justification

A lot of projects require a header with a copyright notice, or they require a license in each file. This 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	Description	Type	Default Value
header	Header	string

Example configuration

<check enabled="true" class="org.scalastyle.file.HeaderMatchesChecker" level="warning">
 <parameters>
  <parameter name="regex">false</parameter>
  <parameter name="header">// Copyright \(C\) 2011-2012 the original author or authors.</parameter>
 </parameters>
</check>

or

<check enabled="true" class="org.scalastyle.file.HeaderMatchesChecker" level="warning">
 <parameters>
  <parameter name="regex">true</parameter>
  <parameter name="header">// Copyright \(C\) (?:\d{4}-)?\d{4} the original author or authors.</parameter>
 </parameters>
</check>

org.scalastyle.file.IndentationChecker - Checks that lines are indented by a multiple of the tab size

id - indentation
description - Checks that lines are indented by a multiple of the tab size
class - org.scalastyle.file.IndentationChecker
default level - WarningLevel

Justification

Code that is not indented consistently can be hard to read.

Parameters

Parameter	Description	Type	Default Value
tabSize	Tab size	integer	2
methodParamIndentSize	Multi-line method parameter spacing	integer	2

Example configuration

<check enabled="true" class="org.scalastyle.file.IndentationChecker" level="warning">
 <parameters>
  <parameter name="tabSize">2</parameter>
  <parameter name="methodParamIndentSize">2</parameter>
 </parameters>
</check>

org.scalastyle.file.NewLineAtEofChecker - Checks that a file ends with a newline character

id - newline.at.eof
description - Checks that a file ends with a newline character
class - org.scalastyle.file.NewLineAtEofChecker
default level - WarningLevel

Justification

Some version control systems don't cope well with files which don't end with a newline character.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.file.NewLineAtEofChecker" level="warning"/>

org.scalastyle.file.NoNewLineAtEofChecker - Checks that a file does not end with a newline character

id - no.newline.at.eof
description - Checks that a file does not end with a newline character
class - org.scalastyle.file.NoNewLineAtEofChecker
default level - WarningLevel

Justification

Because Mirco Dotta wanted it.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.file.NoNewlineAtEofChecker" level="warning"/>

org.scalastyle.file.RegexChecker - Checks that a regular expression cannot be matched, if found reports this

id - regex
description - Checks that a regular expression cannot be matched, if found reports this
class - org.scalastyle.file.RegexChecker
default level - WarningLevel

Justification

Some checks can be carried out with a regular expression.

Parameters

Parameter	Description	Type	Default Value
regex	Regular expression	string
line	Line	boolean	false

Example configuration

<check enabled="true" class="org.scalastyle.file.RegexChecker" level="warning">
 <parameters>
  <parameter name="regex">(?m)^\s*$(\r|)\n^\s*$(\r|)\n</parameter>
  <parameter name="line">false</parameter>
 </parameters>
 <customMessage>No double blank lines</customMessage>
</check>

org.scalastyle.file.WhitespaceEndOfLineChecker - Check that there is no trailing whitespace at the end of lines

id - whitespace.end.of.line
description - Check that there is no trailing whitespace at the end of lines
class - org.scalastyle.file.WhitespaceEndOfLineChecker
default level - WarningLevel

Justification

Whitespace at the end of a line can cause problems when diffing between files or between versions.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.file.WhitespaceEndOfLineChecker" level="warning"/>

org.scalastyle.scalariform.BlockImportChecker - Checks that block imports are not used.

id - block.import
description - Checks that block imports are not used.
class - org.scalastyle.scalariform.BlockImportChecker
default level - WarningLevel

Justification

Block imports can lead to annoying merge errors in large code bases that are maintained by lot of developers. This rule allows to ensure that only single imports are used in order to minimize merge errors in import declarations.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.BlockImportChecker" level="warning"/>

org.scalastyle.scalariform.ClassNamesChecker - Check that class names match a regular expression

id - class.name
description - Check that class names match a regular expression
class - org.scalastyle.scalariform.ClassNamesChecker
default level - WarningLevel

Justification

The Scala style guide recommends that class names conform to certain standards.

Parameters

Parameter	Description	Type	Default Value
regex	Regular expression	string	^[A-Z][A-Za-z]*$

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ClassNamesChecker" level="warning">
 <parameters>
  <parameter name="regex">^[A-Z][A-Za-z]*$</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.ClassTypeParameterChecker - Checks that type parameter to a class matches a regular expression

id - class.type.parameter.name
description - Checks that type parameter to a class matches a regular expression
class - org.scalastyle.scalariform.ClassTypeParameterChecker
default level - WarningLevel

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	Description	Type	Default Value
regex	Regular expression	string	^[A-Z_]$

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ClassTypeParameterChecker" level="warning">
 <parameters>
  <parameter name="regex">^[A-Z_]$</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.CovariantEqualsChecker - Check that classes and objects do not define equals without overriding equals(java.lang.Object).

id - covariant.equals
description - Check that classes and objects do not define equals without overriding equals(java.lang.Object).
class - org.scalastyle.scalariform.CovariantEqualsChecker
default level - WarningLevel

Justification

Mistakenly defining a covariant equals() method without overriding method equals(java.lang.Object) can produce unexpected runtime behaviour.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.CovariantEqualsChecker" level="warning"/>

org.scalastyle.scalariform.CyclomaticComplexityChecker - Checks that the cyclomatic complexity of a method does exceed a value

id - cyclomatic.complexity
description - Checks that the cyclomatic complexity of a method does exceed a value
class - org.scalastyle.scalariform.CyclomaticComplexityChecker
default level - WarningLevel

Justification

If the code is too complex, then this can make code hard to read.

Parameters

Parameter	Description	Type	Default Value
maximum	Maximum	integer	10

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.CyclomaticComplexityChecker" level="warning">
 <parameters>
  <parameter name="maximum">10</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.DeprecatedJavaChecker - Checks that Java @Deprecated is not used, Scala @deprecated should be used instead

id - deprecated.java
description - Checks that Java @Deprecated is not used, Scala @deprecated should be used instead
class - org.scalastyle.scalariform.DeprecatedJavaChecker
default level - WarningLevel

Justification

You should be using the Scala @deprecated instead.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.DeprecatedJavaChecker" level="warning"/>

org.scalastyle.scalariform.DisallowSpaceAfterTokenChecker - Disallow space after certain token(s)

id - disallow.space.after.token
description - Disallow space after certain token(s)
class - org.scalastyle.scalariform.DisallowSpaceAfterTokenChecker
default level - WarningLevel

Justification

Correct formatting can help readability.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.DisallowSpaceAfterTokenChecker" level="warning">
 <parameters>
  <parameter name="tokens">LPAREN</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.DisallowSpaceBeforeTokenChecker - Disallow space before certain token(s)

id - disallow.space.before.token
description - Disallow space before certain token(s)
class - org.scalastyle.scalariform.DisallowSpaceBeforeTokenChecker
default level - WarningLevel

Justification

Correct formatting can help readability.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.DisallowSpaceBeforeTokenChecker" level="warning">
 <parameters>
  <parameter name="tokens">COLON, COMMA, RPAREN</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.EmptyClassChecker - If a class/trait has no members, the braces are unnecessary

id - empty.class
description - If a class/trait has no members, the braces are unnecessary
class - org.scalastyle.scalariform.EmptyClassChecker
default level - WarningLevel

Justification

If a class / trait has no members, then braces are unnecessary, and can be removed.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.EmptyClassChecker" level="warning"/>

org.scalastyle.scalariform.EnsureSingleSpaceAfterTokenChecker - Ensure single space after certain token(s)

id - ensure.single.space.after.token
description - Ensure single space after certain token(s)
class - org.scalastyle.scalariform.EnsureSingleSpaceAfterTokenChecker
default level - WarningLevel

Justification

Correct formatting can help readability.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.EnsureSingleSpaceAfterTokenChecker" level="warning">
 <parameters>
  <parameter name="tokens">COLON, IF</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.EnsureSingleSpaceBeforeTokenChecker - Ensure single space before certain token(s)

id - ensure.single.space.before.token
description - Ensure single space before certain token(s)
class - org.scalastyle.scalariform.EnsureSingleSpaceBeforeTokenChecker
default level - WarningLevel

Justification

Correct formatting can help readability.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.EnsureSingleSpaceBeforeTokenChecker" level="warning">
 <parameters>
  <parameter name="tokens">LPAREN</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.EqualsHashCodeChecker - Check that if a class implements either equals or hashCode, it should implement the other

id - equals.hash.code
description - Check that if a class implements either equals or hashCode, it should implement the other
class - org.scalastyle.scalariform.EqualsHashCodeChecker
default level - WarningLevel

Justification

Defining either equals or hashCode in a class without defining the is a known source of bugs. Usually, when you define one, you should also define the other.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.EqualsHashCodeChecker" level="warning"/>

org.scalastyle.scalariform.FieldNamesChecker - Check that field names match a regular expression

id - field.name
description - Check that field names match a regular expression
class - org.scalastyle.scalariform.FieldNamesChecker
default level - WarningLevel

Justification

A consistent naming convention for field names can make code easier to read and understand

Parameters

Parameter	Description	Type	Default Value
regex	Regular expression	string	^[a-z][A-Za-z0-9]*$

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.FieldNamesChecker" level="warning">
 <parameters>
  <parameter name="regex">^[a-z][A-Za-z0-9]*$</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.ForBraceChecker - Checks that braces are used in for comprehensions

id - for.brace
description - Checks that braces are used in for comprehensions
class - org.scalastyle.scalariform.ForBraceChecker
default level - WarningLevel

Justification

Usage of braces (rather than parentheses) within a for comprehension mean 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.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ForBraceChecker" level="warning"/>

org.scalastyle.scalariform.IfBraceChecker - Checks that if statements have braces

id - if.brace
description - Checks that if statements have braces
class - org.scalastyle.scalariform.IfBraceChecker
default level - WarningLevel

Justification

Some people find if clauses with braces easier to read.

Description

The singleLineAllowed property allows if constructions of the type:

if (bool_expression) expression1 else expression2

The doubleLineAllowed property allows if constructions of the type:

if (bool_expression) expression1
else expression2

Note: If you intend to enable only if expressions in the format below, disable the IfBraceChecker altogether.

if (bool_expression)
  expression1
else
  expression2

Parameters

Parameter	Description	Type	Default Value
singleLineAllowed	Single Line Allowed	boolean	true
doubleLineAllowed	Double Line Allowed	boolean	false

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.IfBraceChecker" level="warning">
 <parameters>
  <parameter name="singleLineAllowed">true</parameter>
  <parameter name="doubleLineAllowed">false</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.IllegalImportsChecker - Check that a class does not import certain classes

id - illegal.imports
description - Check that a class does not import certain classes
class - org.scalastyle.scalariform.IllegalImportsChecker
default level - WarningLevel

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	Description	Type	Default Value
illegalImports	Illegal Imports	string	sun._,java.awt._

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.IllegalImportsChecker" level="warning"/>

org.scalastyle.scalariform.ImportGroupingChecker - Checks that imports are grouped together, not throughout the file

id - import.grouping
description - Checks that imports are grouped together, not throughout the file
class - org.scalastyle.scalariform.ImportGroupingChecker
default level - WarningLevel

Justification

If imports are spread throughout the file, knowing what is in scope at any one place can be difficult to work out.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ImportGroupingChecker" level="warning"/>

org.scalastyle.scalariform.ImportOrderChecker - Checks that imports are grouped and ordered according to the style configuration.

id - import.ordering
description - Checks that imports are grouped and ordered according to the style configuration.
class - org.scalastyle.scalariform.ImportOrderChecker
default level - WarningLevel

Justification

Consistent import ordering improves code readability and reduces unrelated changes in patches.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ImportOrderChecker" level="warning">
 <parameters>
  <parameter name="groups">java,scala,others</parameter>
  <parameter name="group.java">javax?\..+</parameter>
  <parameter name="group.scala">scala\..+</parameter>
  <parameter name="group.others">.+</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.LowercasePatternMatchChecker - Checks that a case statement pattern match is not lower case, as this can cause confusion

id - lowercase.pattern.match
description - Checks that a case statement pattern match is not lower case, as this can cause confusion
class - org.scalastyle.scalariform.LowercasePatternMatchChecker
default level - WarningLevel

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"

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.LowercasePatternMatchChecker" level="warning"/>

org.scalastyle.scalariform.MagicNumberChecker - Checks for use of magic numbers

id - magic.number
description - Checks for use of magic numbers
class - org.scalastyle.scalariform.MagicNumberChecker
default level - WarningLevel

Justification

Replacing a magic number with a named constant can make code easier to read and understand, and can avoid some subtle bugs.

Description

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	Description	Type	Default Value
ignore	Ignore	string	-1,0,1,2

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.MagicNumberChecker" level="warning">
 <parameters>
  <parameter name="ignore">-1,0,1,2,3</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.MethodLengthChecker - Checks that methods do not exceed a maximum length

id - method.length
description - Checks that methods do not exceed a maximum length
class - org.scalastyle.scalariform.MethodLengthChecker
default level - WarningLevel

Justification

Long methods can be hard to read and understand.

Parameters

Parameter	Description	Type	Default Value
maxLength	Maximum length	integer	50

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.MethodLengthChecker" level="warning">
 <parameters>
  <parameter name="maxLength">50</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.MethodNamesChecker - Check that method names match a regular expression

id - method.name
description - Check that method names match a regular expression
class - org.scalastyle.scalariform.MethodNamesChecker
default level - WarningLevel

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

Parameter	Description	Type	Default Value
regex	Regular expression	string	^[a-z][A-Za-z0-9]*(_=)?$
ignoreRegex	Regular expression to ignore	string	^$
ignoreOverride	Ignore override	boolean	false

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.MethodNamesChecker" level="warning">
 <parameters>
  <parameter name="regex">^[A-Za-z]*$</parameter>
  <parameter name="ignoreRegex">^.*$</parameter>
  <parameter name="ignoreOverride">false</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.MultipleStringLiteralsChecker - Checks that a string literal does not appear multiple times

id - multiple.string.literals
description - Checks that a string literal does not appear multiple times
class - org.scalastyle.scalariform.MultipleStringLiteralsChecker
default level - WarningLevel

Justification

Code duplication makes maintenance more difficult, so it can be better to replace the multiple occurrences with a constant.

Parameters

Parameter	Description	Type	Default Value
allowed	Maximum occurences allowed	integer	1
ignoreRegex	Ignore regular expression	string	^""$

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.MultipleStringLiteralsChecker" level="warning">
 <parameters>
  <parameter name="allowed">1</parameter>
  <parameter name="ignoreRegex">^\&quot;\&quot;$</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.NoCloneChecker - Check that classes and objects do not define the clone() method

id - no.clone
description - Check that classes and objects do not define the clone() method
class - org.scalastyle.scalariform.NoCloneChecker
default level - WarningLevel

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 pages.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.NoCloneChecker" level="warning"/>

org.scalastyle.scalariform.NoFinalizeChecker - Check that classes and objects do not define the finalize() method

id - no.finalize
description - Check that classes and objects do not define the finalize() method
class - org.scalastyle.scalariform.NoFinalizeChecker
default level - WarningLevel

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 finalize() method.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.NoFinalizeChecker" level="warning"/>

org.scalastyle.scalariform.NoWhitespaceAfterLeftBracketChecker - No whitespace after left bracket '['

id - no.whitespace.after.left.bracket
description - No whitespace after left bracket '['
class - org.scalastyle.scalariform.NoWhitespaceAfterLeftBracketChecker
default level - WarningLevel

Justification

If there is whitespace after a left bracket, this can be confusing to the reader

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.NoWhitespaceAfterLeftBracketChecker" level="warning"/>

org.scalastyle.scalariform.NoWhitespaceBeforeLeftBracketChecker - No whitespace before left bracket '['

id - no.whitespace.before.left.bracket
description - No whitespace before left bracket '['
class - org.scalastyle.scalariform.NoWhitespaceBeforeLeftBracketChecker
default level - WarningLevel

Justification

If there is whitespace before a left bracket, this can be confusing to the reader

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.NoWhitespaceBeforeLeftBracketChecker" level="warning"/>

org.scalastyle.scalariform.NonASCIICharacterChecker - Some editors are unfriendly to non ascii characters.

id - non.ascii.character.disallowed
description - Some editors are unfriendly to non ascii characters.
class - org.scalastyle.scalariform.NonASCIICharacterChecker
default level - WarningLevel

Justification

Scala allows unicode characters as operators and some editors misbehave when they see non-ascii character. In a project collaborated by a community of developers. This check can be helpful in such situations.

        "value".match {
        case "value" => println("matched")
        ...
        }

        is preferred to

        "value".match {
        case "value" ⇒ println("matched")
        ...
        }

        To fix it, replace the (unicode operator)⇒ with =>.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.NonASCIICharacterChecker" level="warning"/>

org.scalastyle.scalariform.NotImplementedErrorUsage - Checks that the code does not have ??? operators.

id - not.implemented.error.usage
description - Checks that the code does not have ??? operators.
class - org.scalastyle.scalariform.NotImplementedErrorUsage
default level - WarningLevel

Justification

The ??? operator denotes that an implementation is missing. This rule helps to avoid potential runtime errors because of not implemented code.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.NotImplementedErrorUsage" level="warning"/>

org.scalastyle.scalariform.NullChecker - Check that null is not used

id - null
description - Check that null is not used
class - org.scalastyle.scalariform.NullChecker
default level - WarningLevel

Justification

Scala discourages use of nulls, preferring Option.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.NullChecker" level="warning"/>

org.scalastyle.scalariform.NumberOfMethodsInTypeChecker - Check that a class / trait / object does not have too many methods

id - number.of.methods
description - Check that a class / trait / object does not have too many methods
class - org.scalastyle.scalariform.NumberOfMethodsInTypeChecker
default level - WarningLevel

Justification

If a type declares too many methods, this can be an indication of bad design.

Parameters

Parameter	Description	Type	Default Value
maxMethods	Maximum methods	integer	30

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.NumberOfMethodsInTypeChecker" level="warning">
 <parameters>
  <parameter name="maxMethods">30</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.NumberOfTypesChecker - Checks that there are not too many types declared in a file

id - number.of.types
description - Checks that there are not too many types declared in a file
class - org.scalastyle.scalariform.NumberOfTypesChecker
default level - WarningLevel

Justification

If there are too many classes/objects defined in a single file, this can cause the code to be difficult to understand.

Parameters

Parameter	Description	Type	Default Value
maxTypes	Maximum Number	integer	20

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.NumberOfTypesChecker" level="warning">
 <parameters>
  <parameter name="maxTypes">20</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.ObjectNamesChecker - Check that object names match a regular expression

id - object.name
description - Check that object names match a regular expression
class - org.scalastyle.scalariform.ObjectNamesChecker
default level - WarningLevel

Justification

The Scala style guide recommends that object names conform to certain standards.

Parameters

Parameter	Description	Type	Default Value
regex	Regular expression	string	^[A-Z][A-Za-z]*$

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ObjectNamesChecker" level="warning">
 <parameters>
  <parameter name="regex">^[A-Z][A-Za-z]*$</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.PackageObjectNamesChecker - Check that package object names match a regular expression

id - package.object.name
description - Check that package object names match a regular expression
class - org.scalastyle.scalariform.PackageObjectNamesChecker
default level - WarningLevel

Justification

The Scala style guide recommends that package object names conform to certain standards.

Parameters

Parameter	Description	Type	Default Value
regex	Regular expression	string	^[a-z][A-Za-z]*$

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.PackageObjectNamesChecker" level="warning">
 <parameters>
  <parameter name="regex">^[a-z][A-Za-z]*$</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.ParameterNumberChecker - Maximum number of parameters for a method

id - parameter.number
description - Maximum number of parameters for a method
class - org.scalastyle.scalariform.ParameterNumberChecker
default level - WarningLevel

Justification

A method which has more than a certain number of parameters can be hard to understand.

Parameters

Parameter	Description	Type	Default Value
maxParameters	Maximum Number	integer	8

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ParameterNumberChecker" level="warning">
 <parameters>
  <parameter name="maxParameters">8</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.PatternMatchAlignChecker - Check that pattern match arrows align

id - pattern.match.align
description - Check that pattern match arrows align
class - org.scalastyle.scalariform.PatternMatchAlignChecker
default level - WarningLevel

Justification

Correct formatting can help readability.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.PatternMatchAlignChecker" level="warning"/>

org.scalastyle.scalariform.ProcedureDeclarationChecker - Use a : Unit = for procedure declarations

id - procedure.declaration
description - Use a : Unit = for procedure declarations
class - org.scalastyle.scalariform.ProcedureDeclarationChecker
default level - WarningLevel

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.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ProcedureDeclarationChecker" level="warning"/>

org.scalastyle.scalariform.PublicMethodsHaveTypeChecker - Check that a method has an explicit return type, it is not inferred

id - public.methods.have.type
description - Check that a method has an explicit return type, it is not inferred
class - org.scalastyle.scalariform.PublicMethodsHaveTypeChecker
default level - WarningLevel

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	Description	Type	Default Value
ignoreOverride	Ignore overridden methods	boolean	false

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.PublicMethodsHaveTypeChecker" level="warning">
 <parameters>
  <parameter name="ignoreOverride">false</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.RedundantIfChecker - Checks that if expressions are not redundant, i.e. easily replaced by a variant of the condition

id - if.redundant
description - Checks that if expressions are not redundant, i.e. easily replaced by a variant of the condition
class - org.scalastyle.scalariform.RedundantIfChecker
default level - WarningLevel

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.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.RedundantIfChecker" level="warning"/>

org.scalastyle.scalariform.ReturnChecker - Check that return is not used

id - return
description - Check that return is not used
class - org.scalastyle.scalariform.ReturnChecker
default level - WarningLevel

Justification

Use of return is not usually necessary in Scala. In fact, use of return can discourage a functional style of programming.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ReturnChecker" level="warning"/>

org.scalastyle.scalariform.ScalaDocChecker - Checks that the ScalaDoc on documentable members is well-formed

id - scaladoc
description - Checks that the ScalaDoc on documentable members is well-formed
class - org.scalastyle.scalariform.ScalaDocChecker
default level - WarningLevel

Justification

Scaladoc is generally considered a good thing. Within reason.

Parameters

Parameter	Description	Type	Default Value
ignoreRegex	Regular expression	string	^$

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.ScalaDocChecker" level="warning">
 <parameters>
  <parameter name="ignoreRegex">(.*Spec$)|(.*SpecIT$)</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.SimplifyBooleanExpressionChecker - Boolean expression can be simplified

id - simplify.boolean.expression
description - Boolean expression can be simplified
class - org.scalastyle.scalariform.SimplifyBooleanExpressionChecker
default level - WarningLevel

Justification

A boolean expression which can be simplified can make code easier to read.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.SimplifyBooleanExpressionChecker" level="warning"/>

org.scalastyle.scalariform.SpaceAfterCommentStartChecker - Checks a space after the start of the comment.

id - space.after.comment.start
description - Checks a space after the start of the comment.
class - org.scalastyle.scalariform.SpaceAfterCommentStartChecker
default level - WarningLevel

Justification

To bring consistency with how comments should be formatted, leave a space right after the beginning of the comment.

package foobar

object Foobar {
/**WRONG
*
*/
/** Correct*/
val d = 2 /*Wrong*/ //Wrong
/**
*Correct
*/
val e = 3/** Correct*/ // Correct
}

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.SpaceAfterCommentStartChecker" level="warning"/>

org.scalastyle.scalariform.SpacesAfterPlusChecker - Check that the plus sign is followed by a space

id - spaces.after.plus
description - Check that the plus sign is followed by a space
class - org.scalastyle.scalariform.SpacesAfterPlusChecker
default level - WarningLevel

Justification

An expression with spaces around + can be easier to read

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.SpacesAfterPlusChecker" level="warning"/>

org.scalastyle.scalariform.SpacesBeforePlusChecker - Check that the plus sign is preceded by a space

id - spaces.before.plus
description - Check that the plus sign is preceded by a space
class - org.scalastyle.scalariform.SpacesBeforePlusChecker
default level - WarningLevel

Justification

An expression with spaces around + can be easier to read

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.BeforePlusChecker" level="warning"/>

org.scalastyle.scalariform.StructuralTypeChecker - Check that structural types are not used.

id - structural.type
description - Check that structural types are not used.
class - org.scalastyle.scalariform.StructuralTypeChecker
default level - WarningLevel

Justification

Structural types in Scala can use reflection - this can have unexpected performance consequences.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.StructuralTypeChecker" level="warning"/>

org.scalastyle.scalariform.TodoCommentChecker - Check for use of TODO/FIXME single line comments

id - todo.comment
description - Check for use of TODO/FIXME single line comments
class - org.scalastyle.scalariform.TodoCommentChecker
default level - WarningLevel

Justification

Some projects may consider TODO or FIXME comments in a code bad style. They would rather you fix the problem.

Parameters

Parameter	Description	Type	Default Value
words	Word list	string	TODO\|FIXME

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.TodoCommentChecker" level="warning">
 <parameters>
  <parameter name="words">TODO|FIXME</parameter>
 </parameters>
</check>

org.scalastyle.scalariform.TokenChecker - Checks that a regular expression cannot be matched in a token, if found reports this

id - token
description - Checks that a regular expression cannot be matched in a token, if found reports this
class - org.scalastyle.scalariform.TokenChecker
default level - WarningLevel

Justification

Some checks can be carried by just the presence of a particular token.

Parameters

Parameter	Description	Type	Default Value
regex	Regular expression	string	^$

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.TokenChecker" level="warning">
 <parameters>
  <parameter name="regex">^[ai]sInstanceOf$</parameter>
 </parameters>
 <customMessage>Avoid casting.</customMessage>
</check>

org.scalastyle.scalariform.UnderscoreImportChecker - Avoid wildcard imports

id - underscore.import
description - Avoid wildcard imports
class - org.scalastyle.scalariform.UnderscoreImportChecker
default level - WarningLevel

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

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.UnderscoreImportChecker" level="warning"/>

org.scalastyle.scalariform.UppercaseLChecker - Checks that if a long literal is used, then an uppercase L is used

id - uppercase.l
description - Checks that if a long literal is used, then an uppercase L is used
class - org.scalastyle.scalariform.UppercaseLChecker
default level - WarningLevel

Justification

A lowercase L (l) can look similar to a number 1 with some fonts.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.UppercaseLChecker" level="warning"/>

org.scalastyle.scalariform.VarFieldChecker - Checks that classes and objects do not define mutable fields

id - var.field
description - Checks that classes and objects do not define mutable fields
class - org.scalastyle.scalariform.VarFieldChecker
default level - WarningLevel

Justification

var (mutable fields) are deprecated if you're using a strict functional style

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.VarFieldChecker" level="warning"/>

org.scalastyle.scalariform.VarLocalChecker - Checks that functions do not define mutable variables

id - var.local
description - Checks that functions do not define mutable variables
class - org.scalastyle.scalariform.VarLocalChecker
default level - WarningLevel

Justification

vars (mutable local variables) loops are deprecated if you're using a strict functional style

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.VarLocalChecker" level="warning"/>

org.scalastyle.scalariform.WhileChecker - Checks that while is not used

id - while
description - Checks that while is not used
class - org.scalastyle.scalariform.WhileChecker
default level - WarningLevel

Justification

while loops are deprecated if you're using a strict functional style

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.WhileChecker" level="warning"/>

org.scalastyle.scalariform.XmlLiteralChecker - Check that XML literals are not used

id - xml.literal
description - Check that XML literals are not used
class - org.scalastyle.scalariform.XmlLiteralChecker
default level - WarningLevel

Justification

Some projects prefer not to have XML literals. They could use a templating engine instead.

Parameters

No parameters

Example configuration

<check enabled="true" class="org.scalastyle.scalariform.XmlLiteralChecker" level="warning"/>

Files

rules-0.8.0.markdown

Latest commit

History

rules-0.8.0.markdown

File metadata and controls

org.scalastyle.file.FileLengthChecker - Check the number of lines in a file

Justification

Parameters

Example configuration

org.scalastyle.file.FileLineLengthChecker - Check the number of characters in a line

Justification

Parameters

Example configuration

org.scalastyle.file.FileTabChecker - Check that there are no tabs in a file

Justification

Parameters

Example configuration

org.scalastyle.file.HeaderMatchesChecker - Check the first lines of each file matches the text

Justification

Parameters

Example configuration

org.scalastyle.file.IndentationChecker - Checks that lines are indented by a multiple of the tab size

Justification

Parameters

Example configuration

org.scalastyle.file.NewLineAtEofChecker - Checks that a file ends with a newline character

Justification

Parameters

Example configuration

org.scalastyle.file.NoNewLineAtEofChecker - Checks that a file does not end with a newline character

Justification

Parameters

Example configuration

org.scalastyle.file.RegexChecker - Checks that a regular expression cannot be matched, if found reports this

Justification

Parameters

Example configuration

org.scalastyle.file.WhitespaceEndOfLineChecker - Check that there is no trailing whitespace at the end of lines

Justification

Parameters

Example configuration

org.scalastyle.scalariform.BlockImportChecker - Checks that block imports are not used.

Justification

Parameters

Example configuration

org.scalastyle.scalariform.ClassNamesChecker - Check that class names match a regular expression

Justification

Parameters

Example configuration

org.scalastyle.scalariform.ClassTypeParameterChecker - Checks that type parameter to a class matches a regular expression

Justification

Parameters

Example configuration

org.scalastyle.scalariform.CovariantEqualsChecker - Check that classes and objects do not define equals without overriding equals(java.lang.Object).

Justification

Parameters

Example configuration

org.scalastyle.scalariform.CyclomaticComplexityChecker - Checks that the cyclomatic complexity of a method does exceed a value

Justification

Parameters

Example configuration

org.scalastyle.scalariform.DeprecatedJavaChecker - Checks that Java @Deprecated is not used, Scala @deprecated should be used instead

Justification

Parameters

Example configuration

org.scalastyle.scalariform.DisallowSpaceAfterTokenChecker - Disallow space after certain token(s)

Justification

Parameters

Example configuration

org.scalastyle.scalariform.DisallowSpaceBeforeTokenChecker - Disallow space before certain token(s)

Justification

Parameters

Example configuration

org.scalastyle.scalariform.EmptyClassChecker - If a class/trait has no members, the braces are unnecessary

Justification

Parameters

Example configuration

org.scalastyle.scalariform.EnsureSingleSpaceAfterTokenChecker - Ensure single space after certain token(s)

Justification