Linter is a Scala static analysis compiler plugin which adds compile-time checks for various possible bugs, inefficiencies, and style problems.
Add Linter to your project by appending this line to your build.sbt:
addCompilerPlugin("org.psywerx.hairyfotr" %% "linter" % "0.1.12")
If you would always like to have the latest changes, snapshots are also available:
resolvers += Resolver.sonatypeRepo("snapshots")
addCompilerPlugin("org.psywerx.hairyfotr" %% "linter" % "0.1-SNAPSHOT")
Another possible way to use Linter is to manually download and use these jars:
Scala 2.11.x,
Scala 2.10.x,
Scala 2.9.3 (outdated)
terminal:
scalac -Xplugin:<path-to-linter-jar>.jar ...
sbt: (in build.sbt)
scalacOptions += "-Xplugin:<path-to-linter-jar>.jar"
maven: (in pom.xml inside scala-maven-plugin configuration)
<configuration>
<args>
<arg>-Xplugin:<path-to-linter-jar>.jar</arg>
</args>
</configuration>
Note: If you have instructions for another build tool or IDE, please make a pull request.
Checks can be disabled using a plus-separated list of check names:
scalacOptions += "-P:linter:disable:UseHypot+CloseSourceFile+OptionOfOption"
Or only specific checks can be enabled using:
scalacOptions += "-P:linter:enable-only:UseHypot+CloseSourceFile+OptionOfOption"
If you believe some warnings are false positives, you can ignore them with a code comment:
scala> val x = math.pow(5, 1/3d) + 1/0 // linter:ignore UseCbrt,DivideByZero // ignores UseCbrt and DivideByZero
<console>:8: warning: Integer division detected in an expression assigned to a floating point variable.
math.pow(5, 1/3d) + 1/0 // linter:ignore UseCbrt,DivideByZero // ignores UseCbrt and DivideByZero
^
scala> val x = math.pow(5, 1/3d) + 1/0 // linter:ignore // ignores all warningsNote: Please consider reporting false positives so that they can be removed in future versions.
UnextendedSealedTrait, UnlikelyEquality, UseLog1p, UseLog10, UseExpm1, UseHypot, UseCbrt, UseSqrt, UseExp, UseAbsNotSqrtSquare, UseIsNanNotSelfComparison, UseIsNanNotNanComparison, UseSignum, BigDecimalNumberFormat, BigDecimalPrecisionLoss, ReflexiveAssignment, CloseSourceFile, JavaConverters, ContainsTypeMismatch, NumberInstanceOf, PatternMatchConstant, PreferIfToBooleanMatch, IdenticalCaseBodies, IdenticalCaseConditions, ReflexiveComparison, YodaConditions, UseConditionDirectly, UseIfExpression, UnnecessaryElseBranch, DuplicateIfBranches, IdenticalIfElseCondition, MergeNestedIfs, VariableAssignedUnusedValue, MalformedSwap, IdenticalIfCondition, IdenticalStatements, IndexingWithNegativeNumber, OptionOfOption, UndesirableTypeInference, AssigningOptionToNull, WrapNullWithOption, AvoidOptionStringSize, AvoidOptionCollectionSize, UseGetOrElseOnOption, UseOptionOrNull, UseOptionGetOrElse, UseExistsNotFindIsDefined, UseExistsNotFilterIsEmpty, UseFindNotFilterHead, UseContainsNotExistsEquals, UseQuantifierFuncNotFold, UseFuncNotReduce, UseFuncNotFold, MergeMaps, FuncFirstThenMap, FilterFirstThenSort, UseMinOrMaxNotSort, UseMapNotFlatMap, UseFilterNotFlatMap, AvoidOptionMethod, TransformNotMap, DuplicateKeyInMap, InefficientUseOfListSize, OnceEvaluatedStatementsInBlockReturningFunction, IntDivisionAssignedToFloat, UseFlattenNotFilterOption, UseExistsNotFilterEmpty, UseCountNotFilterLength, UseExistsNotCountCompare, PassPartialFunctionDirectly, UnitImplicitOrdering, RegexWarning, InvariantCondition, DecomposingEmptyCollection, InvariantExtrema, UnnecessaryMethodCall, ProducesEmptyCollection, OperationAlwaysProducesZero, ModuloByOne, DivideByOne, DivideByZero, ZeroDivideBy, UseUntilNotToMinusOne, InvalidParamToRandomNextInt, UnusedForLoopIteratorValue, StringMultiplicationByNonPositive, LikelyIndexOutOfBounds, UnnecessaryReturn, InvariantReturn, UnusedParameter, InvalidStringFormat, InvalidStringConversion, UnnecessaryStringNonEmpty, UnnecessaryStringIsEmpty, PossibleLossOfPrecision, UnsafeAbs, TypeToType, EmptyStringInterpolator, UnlikelyToString, UnthrownException, SuspiciousMatches, IfDoWhile
Note: Links currently go to the test for that check.
scala> if (a == 10 || b == 10) 0 else if (a == 20 && b == 10) 1 else 2
<console>:10: warning: This condition has appeared earlier in the if-else chain and will never hold here.
if (a == 10 || b == 10) 0 else if (a == 20 && b == 10) 1 else 2
^scala> if (b > 4) (2,a) else (2,a)
<console>:9: warning: If statement branches have the same structure.
if (b > 4) (2,a) else (2,a)
^scala> if (a == b) true else false
<console>:9: warning: Remove the if expression and use the condition directly.
if (a == b) true else false
^scala> (x,y) match { case (a,5) if a > 5 => 0 case (c,5) if c > 5 => 1 }
<console>:10: warning: Identical case condition detected above. This case will never match.
(x,y) match { case (a,5) if a > 5 => 0 case (c,5) if c > 5 => 1 }
^scala> a match { case 3 => "hello" case 4 => "hello" case 5 => "hello" case _ => "how low" }
<console>:9: warning: Bodies of 3 neighbouring cases are identical and could be merged.
a match { case 3 => "hello" case 4 => "hello" case 5 => "hello" case _ => "how low" }
^scala> bool match { case true => 0 case false => 1 }
<console>:9: warning: Pattern matching on Boolean is probably better written as an if statement.
a match { case true => 0 case false => 1 }
^scala> for (i <- 10 to 20) { if (i > 20) "" }
<console>:8: warning: This condition will never hold.
for (i <- 10 to 20) { if (i > 20) "" }
^scala> for (i <- 1 to 10) { 1/(i-1) }
<console>:8: warning: You will likely divide by zero here.
for (i <- 1 to 10) { 1/(i-1) }
^scala> { val a = List(1,2,3); for (i <- 1 to 10) { println(a(i)) } }
<console>:8: warning: You will likely use a too large index.
{ val a = List(1,2,3); for (i <- 1 to 10) { println(a(i)) } }
^scala> for (i <- 10 to 20) { if (i.toString.length == 3) "" }
<console>:8: warning: This condition will never hold.
for (i <- 10 to 20) { if (i.toString.length == 3) "" }
^scala> { val a = "hello"+util.Random.nextString(10)+"world"+util.Random.nextString(10)+"!"; if (a contains "world") ""; if (a startsWith "hell") "" }
<console>:8: warning: This contains will always returns the same value: true
{ val a = "hello"+util.Random.nextString(10)+"world"+util.Random.nextString(10)+"!"; if (a contains "world") ""; if (a startsWith "hell") "" }
^
<console>:8: warning: This startsWith always returns the same value: true
{ val a = "hello"+util.Random.nextString(10)+"world"+util.Random.nextString(10)+"!"; if (a contains "world") ""; if (a startsWith "hell") "" }
^scala> str.replaceAll("?", ".")
<console>:9: warning: Regex pattern syntax error: Dangling meta character '?'
str.replaceAll("?", ".")
^scala> math.log(1d + a)
<console>:9: warning: Use math.log1p(x), instead of math.log(1 + x) for added accuracy when x is near 0.
math.log(1 + a)
^scala> BigDecimal(0.555555555555555555555555555)
<console>:8: warning: Possible loss of precision. Literal cannot be represented exactly by Double. (0.555555555555555555555555555 != 0.5555555555555556)
BigDecimal(0.555555555555555555555555555)
^scala> val a = Some(List(1,2,3)); if (a.size > 3) ""
<console>:9: warning: Did you mean to take the size of the collection inside the Option?
if (a.size > 3) ""
^scala> if (strOption.isDefined) strOption.get else ""
<console>:9: warning: Use strOption.getOrElse(...) instead of if (strOption.isDefined) strOption.get else ...
if (strOption.isDefined) strOption.get else ""
^scala> List(1,2,3,4).find(x => x % 2 == 0).isDefined
<console>:8: warning: Use col.exists(...) instead of col.find(...).isDefined.
List(1,2,3,4).find(x => x % 2 == 0).isDefined
^scala> List(1,2,3,4).flatMap(x => if (x % 2 == 0) List(x) else Nil)
<console>:8: warning: Use col.filter(x => condition) instead of col.flatMap(x => if (condition) ... else ...).
List(1,2,3,4).flatMap(x => if (x % 2 == 0) List(x) else Nil)
^scala> def func(b: Int, c: String, d: String) = { println(b); b+c }
<console>:7: warning: Parameter d is not used in method func
def func(b: Int, c: String, d: String) = { println(b); b+c }
^scala> List(1, 2, 3).contains("4")
<console>:29: warning: List[Int].contains(String) will probably return false, since the collection and target element are of unrelated types.
List(1, 2, 3).contains("4")
^scala> Nil == None
<console>:29: warning: Comparing with == on instances of unrelated types (scala.collection.immutable.Nil.type, None.type) will probably return false.
Nil == None
^- Improve documentation (bug/style/optimization, most valuable checks, descriptions, ...)
- Improve testing (larger samples, generated tests, link test names to check names, ...)
- Choose whether specific checks should return warnings or errors
- Add more checks
- Reduce false positive rate
- Check out new stuff such as quasiquotes
- Figure out why some tests fail on Scala 2.11
Feel free to add your own ideas, or implement these. Pull requests welcome!
- Require explicit
overridewhenever a method is being overridden - Expressions spanning multiple lines should be enclosed in parentheses
- Traversable#head, Traversable#last, Traversable#maxBy
- Warn on shadowing variables, especially those of the same type (
var a = 4; { val a = 5 }) - Warn on inexhaustive pattern matching or unreachable cases
- Boolean function parameters should be named (
func("arg1", force = true)) - Detect vars, that could easily be vals (done in scala 2.11 -Xlint)
Rule lists from other static analysis tools:
- ScalaStyle(Scala) - https://github.com/scalastyle/scalastyle/wiki
- Scapegoat(Scala) - https://github.com/sksamuel/scalac-scapegoat-plugin#inspections
- WartRemover(Scala) - https://github.com/typelevel/wartremover#warts
- Scala Abide(Scala) - https://github.com/scala/scala-abide
- ($)SuperSafe™(Scala) - http://www.artima.com/supersafe_user_guide.html
- IntelliJ IDEA(Scala/...) - https://www.jetbrains.com/idea/features/scala.html
- Findbugs(JVM) - http://findbugs.sourceforge.net/bugDescriptions.html
- ($)Julia(JVM) - http://www.juliasoft.com/warnings
- CheckStyle(Java) - http://checkstyle.sourceforge.net/availablechecks.html
- PMD(Java) - http://pmd.sourceforge.net/snapshot/pmd-java/rules/index.html
- Error-prone(Java) - https://code.google.com/p/error-prone/wiki/BugPatterns
- CodeNarc(Groovy) - http://codenarc.sourceforge.net/codenarc-rule-index.html
- Shellcheck(shell) - http://www.shellcheck.net/about.html
- ($)PVS-Studio(C++) - http://www.viva64.com/en/d/
- ($)Coverity(C++/Java/...) - http://www.slideshare.net/Coverity/static-analysis-primer-22874326 (6,7)
- CppCheck(C++) - http://sourceforge.net/p/cppcheck/wiki/ListOfChecks/
- Clang(C++/ObjC) - http://clang-analyzer.llvm.org/available_checks.html
- OCLint(C++/ObjC) - http://docs.oclint.org/en/dev/rules/index.html
- ($)Fortify(Java/C++/...) - http://www.hpenterprisesecurity.com/vulncat/en/vulncat/index.html
- Infer(Java/C/ObjC) - http://fbinfer.com/docs/infer-bug-types.html
- A repo with various resources about the scala compiler: https://github.com/illandan/scala.compiler.guides
- A quick overview of writing compiler plugins: http://www.scala-lang.org/node/140
- Basic tree example, and list of AST elements: http://stackoverflow.com/q/10419101/293115
- Notes on compiler plugins from ScalaCL: http://code.google.com/p/scalacl/wiki/WritingScalaCompilerPlugins
- Notes and a similar compiler plugin from a while ago: https://github.com/ymasory/alacs/blob/master/dev/resources.md
- Great article about practical static analysis from Coverity authors: http://cacm.acm.org/magazines/2010/2/69354-a-few-billion-lines-of-code-later/fulltext
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent