Add support for the 3 last versions of scala for each binary version …

…for ExplicitResultType rule

We were failing if the scalaversion is not exactly the same than the one used to compile
explicitResultType rule. Now it can work with the 3 last versions, and we have tests to verify that it works as expected

.github/workflows/ci.yml

@@ -19,6 +19,13 @@ jobs:
       - uses: actions/checkout@v2
       - uses: olafurpg/setup-scala@v7
       - run: sbt ${{ matrix.command }}
+  ci-explicit-result-types-test:
+    name: ci-explicit-result-types-rule tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: olafurpg/setup-scala@v7
+      - run: sbt ci-explicit-result-types-rule
   jdk11_212:
     name: JDK11/scala_2.12 tests
     runs-on: ubuntu-latest

build.sbt

@@ -217,8 +217,11 @@ lazy val unit = project
         "outputSourceDirectories",
         sourceDirectories.in(testsOutput, Compile).value
       )
-      props.put("scalaVersion", scalaVersion.value)
-      props.put("scalacOptions", scalacOptions.value.mkString("|"))
+      props.put("scalaVersion", scalaVersion.in(testsInput, Compile).value)
+      props.put(
+        "scalacOptions",
+        scalacOptions.in(testsInput, Compile).value.mkString("|")
+      )
       val out =
         managedResourceDirectories.in(Test).value.head /
           "scalafix-testkit.properties"

project/Dependencies.scala

@@ -1,4 +1,6 @@
 import sbt._
+
+import scala.util.{Properties, Try}
 /* scalafmt: { maxColumn = 120 }*/
 
 object Dependencies {
@@ -11,6 +13,10 @@ object Dependencies {
   def coursierV = "2.0.0-RC5-6"
   def coursierInterfaceV = "0.0.22"
   val currentScalaVersion = scala213
+  // we support 3 last binary versions of each scala Version, except for 2.11 because semanticdb-scalac_2.11.10 is missing.
+  val supportedScalaVersionforExplicitResultRule =
+    List(scala213, scala212).map(version => version -> supportedScalaVersions(version)).toMap ++
+      Map(scala211 -> List(scala211))
 
   val jgit = "org.eclipse.jgit" % "org.eclipse.jgit" % "5.7.0.202003110725-r"
 
@@ -36,4 +42,13 @@ object Dependencies {
     "com.chuusai" %% "shapeless" % "2.3.3",
     scalacheck
   )
+
+  private def supportedScalaVersions(scalaVersion: String): List[String] = {
+    val split = scalaVersion.split('.')
+    val binaryVersion = split.take(2).mkString(".")
+    val compilerVersion = Try(split.last.toInt).toOption
+    val supportedVersions =
+      compilerVersion.map(version => List.range(version - 2, version + 1).filter(_ >= 0)).getOrElse(Nil)
+    supportedVersions.map(v => s"$binaryVersion.$v")
+  }
 }

project/ScalafixBuild.scala

@@ -67,6 +67,7 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
         "scalameta" -> scalametaV,
         scalaVersion,
         "supportedScalaVersions" -> supportedScalaVersions,
+        "supportedScalaVersionsForExplicitResultTypeRule" -> supportedScalaVersionforExplicitResultRule,
         "scala211" -> scala211,
         "scala212" -> scala212,
         "scala213" -> scala213,
@@ -212,6 +213,21 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
         s"unit/testOnly -- -l scalafix.internal.tests.utils.SkipWindows" ::
         s
     },
+    commands += Command.command("ci-explicit-result-types-rule") { s =>
+      supportedScalaVersionforExplicitResultRule
+        .flatMap {
+          case (k, versions) =>
+            versions.flatMap { v =>
+              List(
+                s"""set ThisBuild/scalaVersion := "$k"""",
+                s"""set  testsInput/scalaVersion := "$v"""",
+                s"""set testsOutput/scalaVersion := "$v\"""",
+                s"unit/testOnly scalafix.tests.rule.RuleSuite -- -z explicitResult"
+              )
+            }
+        }
+        .foldRight(s)(_ :: _)
+    },
     commands += Command.command("mima") { s =>
       // Disabled until v0.6.0 stable
       // "scalafix/mimaReportBinaryIssues" ::

scalafix-rules/src/main/scala/scalafix/internal/rule/ExplicitResultTypes.scala

@@ -6,10 +6,12 @@ import scalafix.patch.Patch
 import scalafix.v1._
 import scalafix.util.TokenOps
 import metaconfig.Configured
+
 import scala.meta.internal.pc.ScalafixGlobal
 import scalafix.internal.v1.LazyValue
+
 import scala.util.control.NonFatal
-import scala.util.Properties
+import scala.util.{Properties, Try}
 import scalafix.internal.compat.CompilerCompat._
 
 final class ExplicitResultTypes(
@@ -19,10 +21,20 @@ final class ExplicitResultTypes(
 
   def this() = this(ExplicitResultTypesConfig.default, LazyValue.now(None))
 
-  private def supportedScalaVersion = Properties.versionNumberString
+  private def supportedScalaVersions: List[String] = {
+    val scalaVersion = Properties.versionNumberString
+    val split = scalaVersion.split('.')
+    val binaryVersion = split.take(2).mkString(".")
+    val compilerVersion = Try(split.last.toInt).toOption
+    val supportedVersions = compilerVersion
+      .map(version => List.range(version - 2, version + 1).filter(_ >= 0))
+      .getOrElse(Nil)
+    supportedVersions.map(v => s"$binaryVersion.$v")
+  }
+
   override def description: String =
     "Inserts type annotations for inferred public members. " +
-      s"Only compatible with Scala $supportedScalaVersion."
+      s"Only compatible with Scala $supportedScalaVersions."
   override def isRewrite: Boolean = true
 
   override def afterComplete(): Unit = {
@@ -57,11 +69,21 @@ final class ExplicitResultTypes(
           )
         }
       }
-    if (config.scalacClasspath.nonEmpty && config.scalaVersion != supportedScalaVersion) {
+    if (config.scalacClasspath.nonEmpty && !supportedScalaVersions.contains(
+        config.scalaVersion
+      )) {
+      val shortScalaVersion =
+        config.scalaVersion.split(".").take(2).mkString(".")
+      val shortRuleScalaVersion =
+        Properties.versionNumberString.split(".").take(2).mkString(".")
       Configured.error(
-        s"The ExplicitResultTypes rule only supports the Scala version '$supportedScalaVersion'. " +
-          s"To fix this problem, either remove `ExplicitResultTypes` from .scalafix.conf or change the Scala version " +
-          s"in your build to match exactly '$supportedScalaVersion'."
+        s"Your scalaVersion is ${config.scalaVersion} but the ExplicitResultTypes rule is compiled with ${shortRuleScalaVersion}" +
+          s"and only supports these Scala versions '$supportedScalaVersions'. " +
+          (if (shortScalaVersion == shortRuleScalaVersion)
+             s"To fix this problem, either remove `ExplicitResultTypes` from .scalafix.conf or change the Scala version to be within '$supportedScalaVersions'"
+           else
+             s"To fix this problem, either remove `ExplicitResultTypes` from .scalafix.conf or " +
+               s"specify a `scalafixScalaBinaryVersion` key in your build.sbt equal to  $shortScalaVersion")
       )
     } else {
       config.conf // Support deprecated explicitReturnTypes config