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https://github.com/hairyfotr/linter
Static Analysis Compiler Plugin for Scala
https://github.com/hairyfotr/linter
abstract-interpretation compiler-plugin linter program-analysis scala static-analysis
Last synced: 4 days ago
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Static Analysis Compiler Plugin for Scala
- Host: GitHub
- URL: https://github.com/hairyfotr/linter
- Owner: HairyFotr
- License: apache-2.0
- Archived: true
- Created: 2013-03-23T12:36:41.000Z (over 11 years ago)
- Default Branch: master
- Last Pushed: 2018-07-10T07:59:26.000Z (about 6 years ago)
- Last Synced: 2024-09-29T02:20:12.455Z (4 days ago)
- Topics: abstract-interpretation, compiler-plugin, linter, program-analysis, scala, static-analysis
- Language: Scala
- Homepage:
- Size: 2.06 MB
- Stars: 267
- Watchers: 18
- Forks: 34
- Open Issues: 22
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Linter Compiler Plugin [](https://travis-ci.org/HairyFotr/linter) [](https://gitter.im/HairyFotr/linter?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [](https://github.com/igrigorik/ga-beacon)
Linter is a Scala static analysis compiler plugin which adds compile-time checks for various possible bugs, inefficiencies, and style problems.
## Donations
Please help support the development of Linter.
[](https://www.paypal.me/HairyFotr/10) [](http://hairyfotr.psywerx.org/linter/32Di22QJoSPt3dAfkACvayBwmsAnfRpAUj.html)
## Usage from sbt
Add Linter to your project by appending this line to your `build.sbt`:
addCompilerPlugin("org.psywerx.hairyfotr" %% "linter" % "0.1.17")
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")
## Usage from maven
Add Linter to your project by updating your `pom.xml` with a "compilerPlugin" section.
org.psywerx.hairyfotr
linter_2.11
0.1.17
## Usage from Jenkins
Use your usual building method and [Jenkins Warnings Plugin](https://wiki.jenkins-ci.org/display/JENKINS/Warnings+Plugin).
## Manual usage
Another possible way to use Linter is to manually download and use these snapshot jars:
[Scala 2.12](https://oss.sonatype.org/content/repositories/snapshots/org/psywerx/hairyfotr/linter_2.12/0.1-SNAPSHOT/linter_2.12-0.1-SNAPSHOT.jar), [Scala 2.11](https://oss.sonatype.org/content/repositories/snapshots/org/psywerx/hairyfotr/linter_2.11/0.1-SNAPSHOT/linter_2.11-0.1-SNAPSHOT.jar), [Scala 2.10](https://oss.sonatype.org/content/repositories/snapshots/org/psywerx/hairyfotr/linter_2.10/0.1-SNAPSHOT/linter_2.10-0.1-SNAPSHOT.jar),
[Scala 2.9.3](https://github.com/HairyFotr/linteRepo/blob/gh-pages/releases/com/foursquare/lint/linter_2.9.3/0.1-SNAPSHOT/linter_2.9.3-0.1-SNAPSHOT.jar?raw=true) (outdated)
terminal:
scalac -Xplugin:.jar ...
sbt: (in build.sbt)
scalacOptions += "-Xplugin:.jar"
maven: (in pom.xml inside scala-maven-plugin configuration)
-Xplugin:.jar
__Note:__ If you have instructions for another build tool or IDE, please make a pull request.
## Displaying check names
To disable displaying check names in the output use the printWarningNames switch:
scalacOptions += "-P:linter:printWarningNames:false"
Note: Set to true by default since version 0.1.17
## Enabling/Disabling checks
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"
## Suppressing false positives
If you believe some warnings are false positives, you can ignore them with a code comment:
```scala
scala> val x = math.pow(5, 1/3d) + 1/0 // linter:ignore UseCbrt,DivideByZero // ignores UseCbrt and DivideByZero
: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 warnings
```
__Note:__ Please consider reporting false positives so that they can be removed in future versions.
## List of implemented checks (123)
[UnextendedSealedTrait](src/test/scala/LinterPluginTest.scala#L1960), [UnlikelyEquality](src/test/scala/LinterPluginTest.scala#L2056), [UseLog1p](src/test/scala/LinterPluginTest.scala#L1044), [UseLog10](src/test/scala/LinterPluginTest.scala#L294), [UseExpm1](src/test/scala/LinterPluginTest.scala#L1090), [UseHypot](src/test/scala/LinterPluginTest.scala#L216), [UseCbrt](src/test/scala/LinterPluginTest.scala#L238), [UseSqrt](src/test/scala/LinterPluginTest.scala#L248), [SuspiciousPow](src/test/scala/LinterPluginTest.scala#L257), [UseExp](src/test/scala/LinterPluginTest.scala#L283), [UseAbsNotSqrtSquare](src/test/scala/LinterPluginTest.scala#L1227), [UseIsNanNotSelfComparison](src/test/scala/LinterPluginTest.scala#L1911), [UseIsNanNotNanComparison](src/test/scala/LinterPluginTest.scala#L1930), [UseSignum](src/test/scala/LinterPluginTest.scala#L1720), BigDecimalNumberFormat, BigDecimalPrecisionLoss, [ReflexiveAssignment](src/test/scala/LinterPluginTest.scala#L1561), [CloseSourceFile](src/test/scala/LinterPluginTest.scala#L827), [JavaConverters](src/test/scala/LinterPluginTest.scala#L838), [ContainsTypeMismatch](src/test/scala/LinterPluginTest.scala#L844), [NumberInstanceOf](src/test/scala/LinterPluginTest.scala#L195), [PatternMatchConstant](src/test/scala/LinterPluginTest.scala#L986), PreferIfToBooleanMatch, [IdenticalCaseBodies](src/test/scala/LinterPluginTest.scala#L937), [IdenticalCaseConditions](src/test/scala/LinterPluginTest.scala#L1785), ReflexiveComparison, [YodaConditions](src/test/scala/LinterPluginTest.scala#L1644), [UseConditionDirectly](src/test/scala/LinterPluginTest.scala#L888), [UseIfExpression](src/test/scala/LinterPluginTest.scala#L146), [UnnecessaryElseBranch](src/test/scala/LinterPluginTest.scala#L156), [DuplicateIfBranches](src/test/scala/LinterPluginTest.scala#L913), [IdenticalIfElseCondition](src/test/scala/LinterPluginTest.scala#L1587), [MergeNestedIfs](src/test/scala/LinterPluginTest.scala#L1667), [VariableAssignedUnusedValue](src/test/scala/LinterPluginTest.scala#L1821), [MalformedSwap](src/test/scala/LinterPluginTest.scala#L1763), IdenticalIfCondition, [IdenticalStatements](src/test/scala/LinterPluginTest.scala#L1893), IndexingWithNegativeNumber, OptionOfOption, [UndesirableTypeInference](src/test/scala/LinterPluginTest.scala#L1797), [AssigningOptionToNull](src/test/scala/LinterPluginTest.scala#L1151), [WrapNullWithOption](src/test/scala/LinterPluginTest.scala#L1159), AvoidOptionStringSize, AvoidOptionCollectionSize, [UseGetOrElseOnOption](src/test/scala/LinterPluginTest.scala#L1166), UseOptionOrNull, UseOptionGetOrElse, [UseExistsNotFindIsDefined](src/test/scala/LinterPluginTest.scala#L1323), [UseExistsNotFilterIsEmpty](src/test/scala/LinterPluginTest.scala#L1342), [UseFindNotFilterHead](src/test/scala/LinterPluginTest.scala#L509), [UseContainsNotExistsEquals](src/test/scala/LinterPluginTest.scala#L727), [UseQuantifierFuncNotFold](src/test/scala/LinterPluginTest.scala#L750), [UseFuncNotReduce](src/test/scala/LinterPluginTest.scala#L787), [UseFuncNotFold](src/test/scala/LinterPluginTest.scala#L768), [MergeMaps](src/test/scala/LinterPluginTest.scala#L1244), [FuncFirstThenMap](src/test/scala/LinterPluginTest.scala#L1253), [FilterFirstThenSort](src/test/scala/LinterPluginTest.scala#L1268), [UseMinOrMaxNotSort](src/test/scala/LinterPluginTest.scala#L1282), [UseMapNotFlatMap](src/test/scala/LinterPluginTest.scala#L1300), [UseFilterNotFlatMap](src/test/scala/LinterPluginTest.scala#L1311), AvoidOptionMethod, [TransformNotMap](src/test/scala/LinterPluginTest.scala#L606), [DuplicateKeyInMap](src/test/scala/LinterPluginTest.scala#L1138), [InefficientUseOfListSize](src/test/scala/LinterPluginTest.scala#L1193), [OnceEvaluatedStatementsInBlockReturningFunction](src/test/scala/LinterPluginTest.scala#L1984), [IntDivisionAssignedToFloat](src/test/scala/LinterPluginTest.scala#L1992), [UseFlattenNotFilterOption](src/test/scala/LinterPluginTest.scala#L1183), [UseCountNotFilterLength](src/test/scala/LinterPluginTest.scala#L646), [UseExistsNotCountCompare](src/test/scala/LinterPluginTest.scala#L684), [PassPartialFunctionDirectly](src/test/scala/LinterPluginTest.scala#L1975), [UnitImplicitOrdering](src/test/scala/LinterPluginTest.scala#L332), [RegexWarning](src/test/scala/LinterPluginTest.scala#L518), [InvariantCondition](src/test/scala/LinterPluginTest.scala#L560), DecomposingEmptyCollection, InvariantExtrema, [UnnecessaryMethodCall](src/test/scala/LinterPluginTest.scala#L1207), ProducesEmptyCollection, [OperationAlwaysProducesZero](src/test/scala/LinterPluginTest.scala#L2267), [ModuloByOne](src/test/scala/LinterPluginTest.scala#L2016), DivideByOne, DivideByZero, ZeroDivideBy, [UseUntilNotToMinusOne](src/test/scala/LinterPluginTest.scala#L1944), [InvalidParamToRandomNextInt](src/test/scala/LinterPluginTest.scala#L2005), UnusedForLoopIteratorValue, StringMultiplicationByNonPositive, LikelyIndexOutOfBounds, UnnecessaryReturn, InvariantReturn, [UnusedParameter](src/test/scala/LinterPluginTest.scala#L1006), [InvalidStringFormat](src/test/scala/LinterPluginTest.scala#L417), InvalidStringConversion, UnnecessaryStringNonEmpty, UnnecessaryStringIsEmpty, [PossibleLossOfPrecision](src/test/scala/LinterPluginTest.scala#L304), [UnsafeAbs](src/test/scala/LinterPluginTest.scala#L344), [TypeToType](src/test/scala/LinterPluginTest.scala#L360), [EmptyStringInterpolator](src/test/scala/LinterPluginTest.scala#L434), [UnlikelyToString](src/test/scala/LinterPluginTest.scala#L445), [UnthrownException](src/test/scala/LinterPluginTest.scala#L458), [SuspiciousMatches](src/test/scala/LinterPluginTest.scala#L467), [PassingNullIntoOption](src/test/scala/LinterPluginTest.scala#L1172), [IfDoWhile](src/test/scala/LinterPluginTest.scala#L578), [FloatingPointNumericRange](src/test/scala/LinterPluginTest.scala#L2028), [UseInitNotReverseTailReverse](src/test/scala/LinterPluginTest.scala#L1454), [UseTakeRightNotReverseTakeReverse](src/test/scala/LinterPluginTest.scala#L1464), [UseLastNotReverseHead](src/test/scala/LinterPluginTest.scala#L1474), [UseFuncNotReverse](src/test/scala/LinterPluginTest.scala#L1487), [UseHeadNotApply](src/test/scala/LinterPluginTest.scala#L1504), [UseLastNotApply](src/test/scala/LinterPluginTest.scala#L1514), [UseHeadOptionNotIf](src/test/scala/LinterPluginTest.scala#L1524), [UseLastOptionNotIf](src/test/scala/LinterPluginTest.scala#L1538), [UseZipWithIndexNotZipIndices](src/test/scala/LinterPluginTest.scala#L1552), [UseGetOrElseNotPatMatch](src/test/scala/LinterPluginTest.scala#L2187), [UseOrElseNotPatMatch](src/test/scala/LinterPluginTest.scala#L2195), [UseOptionFlatMapNotPatMatch](src/test/scala/LinterPluginTest.scala#L2203), UseOptionMapNotPatMatch, [UseOptionFlattenNotPatMatch](src/test/scala/LinterPluginTest.scala#L2219), [UseOptionForeachNotPatMatch](src/test/scala/LinterPluginTest.scala#L2227), [UseOptionIsDefinedNotPatMatch](src/test/scala/LinterPluginTest.scala#L2235), [UseOptionIsEmptyNotPatMatch](src/test/scala/LinterPluginTest.scala#L2243), [UseOptionForallNotPatMatch](src/test/scala/LinterPluginTest.scala#L2259), [UseOptionExistsNotPatMatch](src/test/scala/LinterPluginTest.scala#L2251)
Links above currently go to the test for that check.
Another file to check out is [Warning.scala](src/main/scala/Warning.scala#L155)
## Examples of reported warnings
### If checks
#### Repeated condition in an else-if chain
```scala
scala> if (a == 10 || b == 10) 0 else if (a == 20 && b == 10) 1 else 2
: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
^
```
#### Identical branches
```scala
scala> if (b > 4) (2,a) else (2,a)
:9: warning: If statement branches have the same structure.
if (b > 4) (2,a) else (2,a)
^
```
#### Unnecessary if
```scala
scala> if (a == b) true else false
:9: warning: Remove the if expression and use the condition directly.
if (a == b) true else false
^
```
### Pattern matching checks
#### Detect some unreachable cases
```scala
scala> (x,y) match { case (a,5) if a > 5 => 0 case (c,5) if c > 5 => 1 }
: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 }
^
```
#### Identical neighbouring cases
```scala
scala> a match { case 3 => "hello" case 4 => "hello" case 5 => "hello" case _ => "how low" }
: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" }
^
```
#### Match better written as if
```scala
scala> bool match { case true => 0 case false => 1 }
:9: warning: Pattern matching on Boolean is probably better written as an if statement.
a match { case true => 0 case false => 1 }
^
```
### Integer checks (some abstract interpretation)
#### Check conditions
```scala
scala> for (i <- 10 to 20) { if (i > 20) "" }
:8: warning: This condition will never hold.
for (i <- 10 to 20) { if (i > 20) "" }
^
```
#### Detect division by zero
```scala
scala> for (i <- 1 to 10) { 1/(i-1) }
:8: warning: You will likely divide by zero here.
for (i <- 1 to 10) { 1/(i-1) }
^
```
#### Detect too large, or negative indices
```scala
scala> { val a = List(1,2,3); for (i <- 1 to 10) { println(a(i)) } }
:8: warning: You will likely use a too large index.
{ val a = List(1,2,3); for (i <- 1 to 10) { println(a(i)) } }
^
```
### String checks (some abstract interpretation)
#### Attempt to verify string length conditions
```scala
scala> for (i <- 10 to 20) { if (i.toString.length == 3) "" }
:8: warning: This condition will never hold.
for (i <- 10 to 20) { if (i.toString.length == 3) "" }
^
```
#### Attempt to track the prefix, suffix, and pieces
```scala
scala> { val a = "hello"+util.Random.nextString(10)+"world"+util.Random.nextString(10)+"!"; if (a contains "world") ""; if (a startsWith "hell") "" }
: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") "" }
^
: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") "" }
^
```
#### Regex syntax warnings
```scala
scala> str.replaceAll("?", ".")
:9: warning: Regex pattern syntax error: Dangling meta character '?'
str.replaceAll("?", ".")
^
```
### Numeric checks
#### Using `log(1 + a)` instead of `log1p(a)`
```scala
scala> math.log(1d + a)
:9: warning: Use math.log1p(x), instead of math.log(1 + x) for added accuracy when x is near 0.
math.log(1 + a)
^
```
#### Loss of precision on BigDecimal
```scala
scala> BigDecimal(0.555555555555555555555555555)
:8: warning: Possible loss of precision. Literal cannot be represented exactly by Double. (0.555555555555555555555555555 != 0.5555555555555556)
BigDecimal(0.555555555555555555555555555)
^
```
### Option checks
#### Using Option.size
```scala
scala> val a = Some(List(1,2,3)); if (a.size > 3) ""
:9: warning: Did you mean to take the size of the collection inside the Option?
if (a.size > 3) ""
^
```
#### Using if-else instead of getOrElse
```scala
scala> if (strOption.isDefined) strOption.get else ""
:9: warning: Use strOption.getOrElse(...) instead of if (strOption.isDefined) strOption.get else ...
if (strOption.isDefined) strOption.get else ""
^
```
### Collection checks
#### Use exists(...) instead of find(...).isDefined
```scala
scala> List(1,2,3,4).find(x => x % 2 == 0).isDefined
:8: warning: Use col.exists(...) instead of col.find(...).isDefined.
List(1,2,3,4).find(x => x % 2 == 0).isDefined
^
```
#### Use filter(...) instead of flatMap(...)
```scala
scala> List(1,2,3,4).flatMap(x => if (x % 2 == 0) List(x) else Nil)
: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)
^
```
### Various possible bugs
#### Unused method parameters
```scala
scala> def func(b: Int, c: String, d: String) = { println(b); b+c }
:7: warning: Parameter d is not used in method func
def func(b: Int, c: String, d: String) = { println(b); b+c }
^
```
#### Unsafe `contains`
```scala
scala> List(1, 2, 3).contains("4")
: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")
^
```
#### Unsafe `==`
```scala
scala> Nil == None
:29: warning: Comparing with == on instances of unrelated types (scala.collection.immutable.Nil.type, None.type) will probably return false.
Nil == None
^
```
## Future Work
* Add more checks
* Improve documentation (bug/style/optimization/numeric, most valuable checks, descriptions, ...)
* Improve testing (larger samples, generated tests, ...)
* Choose whether specific checks should return warnings or errors
* Reduce false positive rate
* Check out quasiquotes
### Ideas for new checks
Feel free to add your own ideas, or implement these. Pull requests welcome!
* 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)`)
* Add some abstract interpretation for collections and floats
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/puffnfresh/wartremover#warts
* Scala Abide(Scala) - https://github.com/scala/scala-abide
* ($)SuperSafe™(Scala) - http://www.artima.com/supersafe_user_guide.html
* Scala Clippy(Scala) - https://scala-clippy.org/
* IntelliJ IDEA(Scala/...) - https://www.jetbrains.com/idea/features/scala.html
* Findbugs(JVM) - http://findbugs.sourceforge.net/bugDescriptions.html
* ($)Julia(JVM) - http://www.juliasoft.com/solutions/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://github.com/google/error-prone
* CodeNarc(Groovy) - http://codenarc.sourceforge.net/codenarc-rule-index.html
* Shellcheck(shell) - http://www.shellcheck.net/about.html
* ($)PVS-Studio(C++) - http://www.viva64.com/en/w/
* ($)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
* Infer(Java/C/ObjC) - http://fbinfer.com/docs/infer-bug-types.html
* ... https://github.com/mre/awesome-static-analysis
* ... https://github.com/mcandre/linters
* ...
### Some resources
* 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/old/node/140
* Basic tree example, and list of AST elements: http://stackoverflow.com/q/10419101/293115
* More AST examples from Wolfe: https://github.com/wolfe-pack/wolfe/wiki/Scala-AST-reference
* 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