add scalafix-loader

Author: bjaglin

CONTRIBUTING.md

@@ -19,6 +19,8 @@ hesitate to ask in the [Discord channel](https://discord.gg/8AHaqGx3Qj).
 
 ### For tool integration
 - `scalafix-interfaces/` Java facade to run rules within an existing JVM instance.
+- `scalafix-loader/` Java implementation to dynamically fetch and load
+  implementations to run rules.
 - `scalafix-versions/` Java implementation to advertize which Scala versions
   `scalafix-cli` is published with.
 

build.sbt

@@ -51,6 +51,22 @@ lazy val versions = project
   .disablePlugins(ScalafixPlugin)
   .dependsOn(interfaces)
 
+lazy val loader = project
+  .in(file("scalafix-loader"))
+  .settings(
+    moduleName := "scalafix-loader",
+    javaSettings,
+    mimaPreviousArtifacts := Set.empty, // TODO: remove after 0.14.3
+    libraryDependencies += lombok % Provided,
+    javacOptions ++= {
+      // https://inside.java/2024/06/18/quality-heads-up/
+      if (jdk > 8) Seq("-proc:full")
+      else Seq() // only backported to Oracle’s 8u release (8u411)
+    }
+  )
+  .disablePlugins(ScalafixPlugin)
+  .dependsOn(interfaces)
+
 // Scala 3 macros vendored separately (i.e. without runtime classes), to
 // shadow Scala 2.13 macros in the Scala 3 compiler classpath, while producing
 // code valid against Scala 2.13 bytecode
@@ -384,6 +400,7 @@ lazy val integration = projectMatrix
   .jvmPlatform(CrossVersion.full, cliScalaVersions)
   .enablePlugins(BuildInfoPlugin)
   .dependsOn(unit % "compile->test")
+  .dependsOn(loader % "compile->test")
 
 lazy val expect = projectMatrix
   .in(file("scalafix-tests/expect"))

project/Dependencies.scala

@@ -21,6 +21,7 @@ object Dependencies {
   val commontTextV = "1.13.1"
   val googleDiffV = "1.3.0"
   val jgitV = "5.13.3.202401111512-r"
+  val lombokV = "1.18.38"
   val metaconfigV = "0.15.0"
   val nailgunV = "0.9.1"
   val scalaXmlV = "2.2.0"
@@ -36,6 +37,7 @@ object Dependencies {
   val coursierInterfaces = "io.get-coursier" % "interface" % coursierInterfaceV
   val googleDiff = "com.googlecode.java-diff-utils" % "diffutils" % googleDiffV
   val jgit = "org.eclipse.jgit" % "org.eclipse.jgit" % jgitV
+  val lombok = "org.projectlombok" % "lombok" % lombokV
   val metaconfig = "org.scalameta" %% "metaconfig-typesafe-config" % metaconfigV
   val metacp = "org.scalameta" %% "metacp" % scalametaV
   val nailgunServer = "com.martiansoftware" % "nailgun-server" % nailgunV

project/Mima.scala

@@ -13,7 +13,10 @@ object Mima {
       ProblemFilters.exclude[ReversedMissingMethodProblem]("scalafix.interfaces.Scalafix.scala33"),
       ProblemFilters.exclude[ReversedMissingMethodProblem]("scalafix.interfaces.Scalafix.scala35"),
       ProblemFilters.exclude[ReversedMissingMethodProblem]("scalafix.interfaces.Scalafix.scala36"),
-      ProblemFilters.exclude[ReversedMissingMethodProblem]("scalafix.interfaces.Scalafix.scala37")
+      ProblemFilters.exclude[ReversedMissingMethodProblem]("scalafix.interfaces.Scalafix.scala37"),
+      ProblemFilters.exclude[ReversedMissingMethodProblem]("scalafix.interfaces.ScalafixArguments.withRepositories"),
+      ProblemFilters.exclude[ReversedMissingMethodProblem]("scalafix.interfaces.ScalafixArguments.withToolDependencyCoordinates"),
+      ProblemFilters.exclude[ReversedMissingMethodProblem]("scalafix.interfaces.ScalafixArguments.withToolDependencyURLs")
     )
   }
 }

project/ScalafixBuild.scala

@@ -41,10 +41,11 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
       autoScalaLibrary := false
     )
 
+    lazy val jdk = System.getProperty("java.specification.version").toDouble
+
     // https://github.com/scalameta/scalameta/issues/2485
     lazy val coreScalaVersions = Seq(scala212, scala213)
     lazy val cliScalaVersions = {
-      val jdk = System.getProperty("java.specification.version").toDouble
       val scala3Versions =
         // Scala 3.5 will never support JDK 23
         if (jdk >= 23) Seq(scala33, scala36, scala37)

scalafix-cli/src/main/scala/scalafix/internal/interfaces/ScalafixArgumentsImpl.scala

@@ -48,39 +48,44 @@ final case class ScalafixArgumentsImpl(args: Args = Args.default)
     }
   }
 
+  override def withRepositories(
+      repositories: util.List[Repository]
+  ): ScalafixArguments =
+    copy(args = args.copy(repositories = repositories.asScala.toList))
+
   override def withRules(rules: util.List[String]): ScalafixArguments =
     copy(args = args.copy(rules = rules.asScala.toList))
 
   override def withToolClasspath(
       customURLs: util.List[URL]
   ): ScalafixArguments =
-    withToolClasspath(
-      customURLs,
-      Nil.asJava,
-      Repository.defaults()
-    )
+    withToolDependencyURLs(customURLs)
 
   override def withToolClasspath(
       customURLs: util.List[URL],
       customDependenciesCoordinates: util.List[String]
   ): ScalafixArguments =
-    withToolClasspath(
-      customURLs,
-      customDependenciesCoordinates,
-      Repository.defaults()
-    )
+    withToolDependencyCoordinates(customDependenciesCoordinates)
+      .withToolDependencyURLs(customURLs)
 
   override def withToolClasspath(
       customURLs: util.List[URL],
       customDependenciesCoordinates: util.List[String],
       repositories: util.List[Repository]
   ): ScalafixArguments = {
+    withRepositories(repositories)
+      .withToolDependencyCoordinates(customDependenciesCoordinates)
+      .withToolDependencyURLs(customURLs)
+  }
 
+  override def withToolDependencyCoordinates(
+      withToolDependencyCoordinates: java.util.List[String]
+  ): ScalafixArguments = {
     val OrganizeImportsCoordinates =
       """com\.github\.liancheng.*:organize-imports:.*""".r
 
     val keptDependencies: Seq[String] =
-      customDependenciesCoordinates.asScala
+      withToolDependencyCoordinates.asScala
         .collect {
           case dep @ OrganizeImportsCoordinates() =>
             args.out.println(
@@ -107,7 +112,7 @@ final case class ScalafixArgumentsImpl(args: Args = Args.default)
       else Versions.scalaVersion
 
     val customDependenciesJARs = ScalafixCoursier.toolClasspath(
-      repositories,
+      args.repositories.asJava,
       keptDependencies.asJava,
       scalaVersionForDependencies
     )
@@ -158,13 +163,23 @@ final case class ScalafixArgumentsImpl(args: Args = Args.default)
         }
       }
 
-    val extraURLs = customURLs.asScala ++ customDependenciesJARs
+    val extraURLs = customDependenciesJARs
       .getFiles()
       .asScala
       .map(_.toURI().toURL())
     val classLoader = new URLClassLoader(
       extraURLs.toArray,
-      getClass.getClassLoader
+      args.toolClasspath
+    )
+    withToolClasspath(classLoader)
+  }
+
+  override def withToolDependencyURLs(
+      withToolDependencyURLs: java.util.List[java.net.URL]
+  ): ScalafixArguments = {
+    val classLoader = new URLClassLoader(
+      withToolDependencyURLs.asScala.toArray,
+      args.toolClasspath
     )
     withToolClasspath(classLoader)
   }

scalafix-cli/src/main/scala/scalafix/internal/v1/Args.scala

@@ -13,6 +13,7 @@ import java.util.regex.Pattern
 import java.util.regex.PatternSyntaxException
 
 import scala.annotation.StaticAnnotation
+import scala.jdk.CollectionConverters._
 import scala.util.Failure
 import scala.util.Success
 import scala.util.Try
@@ -22,6 +23,8 @@ import scala.meta.internal.symtab.SymbolTable
 import scala.meta.io.AbsolutePath
 import scala.meta.io.Classpath
 
+import coursierapi.MavenRepository
+import coursierapi.Repository
 import metaconfig.Configured._
 import metaconfig._
 import metaconfig.annotation._
@@ -158,6 +161,8 @@ case class Args(
         "The glob syntax is defined by `nio.FileSystem.getPathMatcher`."
     )
     exclude: List[PathMatcher] = Nil,
+    @Description("Maven repositories to fetch the artifacts from")
+    repositories: List[Repository] = Repository.defaults.asScala.toList,
     @Description(
       "Additional classpath for compiling and classloading custom rules, as a set of filesystem paths, separated by ':' on Unix or ';' on Windows."
     )
@@ -483,6 +488,8 @@ object Args extends TPrintImplicits {
     ConfDecoder.stringConfDecoder.map(glob =>
       FileSystems.getDefault.getPathMatcher("glob:" + glob)
     )
+  implicit val repositoryDecoder: ConfDecoder[Repository] =
+    ConfDecoder.stringConfDecoder.map(base => MavenRepository.of(base))
   implicit val scalaVersionDecoder: ConfDecoder[ScalaVersion] =
     ScalafixConfig.scalaVersionDecoder
 
@@ -505,6 +512,8 @@ object Args extends TPrintImplicits {
     ConfEncoder.StringEncoder.contramap(_ => "<stdout>")
   implicit val pathMatcherEncoder: ConfEncoder[PathMatcher] =
     ConfEncoder.StringEncoder.contramap(_.toString)
+  implicit val repositoriesEncoder: ConfEncoder[Repository] =
+    ConfEncoder.StringEncoder.contramap(_.toString)
   implicit val callbackEncoder: ConfEncoder[ScalafixMainCallback] =
     ConfEncoder.StringEncoder.contramap(_.toString)
   implicit val argsEncoder: ConfEncoder[Args] = generic.deriveEncoder

scalafix-interfaces/src/main/java/scalafix/interfaces/Scalafix.java

@@ -1,6 +1,7 @@
 package scalafix.interfaces;
 
 import coursierapi.Repository;
+
 import scalafix.internal.interfaces.ScalafixCoursier;
 import scalafix.internal.interfaces.ScalafixInterfacesClassloader;
 import scalafix.internal.interfaces.ScalafixProperties;
@@ -11,16 +12,21 @@
 import java.lang.reflect.InvocationTargetException;
 import java.net.URL;
 import java.net.URLClassLoader;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Properties;
+import java.util.ServiceLoader;
 
 /**
- * Public API for reflectively invoking Scalafix from a build tool or IDE integration.
+ * Public API for reflectively invoking Scalafix from a build tool or IDE
+ * integration.
  * <p>
- * To obtain an instance of Scalafix, use one of the static factory methods.
+ * To obtain an instance of Scalafix, classload
+ * <code>ch.epfl.scala:scalafix-loader</code> and use {@link #get()}.
  *
- * @implNote This interface is not intended to be extended, the only implementation of this interface
- * should live in the Scalafix repository.
+ * @implNote This interface is not intended to be extended, the only
+ *           implementation of this interface should live in the Scalafix
+ *           repository.
  */
 public interface Scalafix {
 
@@ -102,44 +108,17 @@ public interface Scalafix {
     String scala3Next();
 
     /**
-     * Fetch JARs containing an implementation of {@link Scalafix} using Coursier and classload an instance of it via
-     * runtime reflection.
-     * <p>
-     * The custom classloader optionally provided with {@link ScalafixArguments#withToolClasspath} to compile and
-     * classload external rules must have the classloader of the returned instance as ancestor to share a common
-     * loaded instance of `scalafix-core`, and therefore have been compiled against the requested Scala version.
-     *
-     * @param requestedScalaVersion A full Scala version (i.e. "3.3.4") or a major.minor one (i.e. "3.3") to infer
-     *                              the major.minor Scala version that should be available in the classloader of the
-     *                              returned instance. To be able to run advanced semantic rules using the Scala
-     *                              Presentation Compiler such as ExplicitResultTypes, this must be source-compatible
-     *                              with the version that the target classpath is built with, as provided with
-     *                              {@link ScalafixArguments#withScalaVersion}.
-     * @return An implementation of the {@link Scalafix} interface.
-     * @throws ScalafixException in case of errors during artifact resolution/fetching.
+     * @deprecated Use {@link #get()} instead.
      */
+    @Deprecated
     static Scalafix fetchAndClassloadInstance(String requestedScalaVersion) throws ScalafixException {
         return fetchAndClassloadInstance(requestedScalaVersion, Repository.defaults());
     }
 
     /**
-     * Fetch JARs containing an implementation of {@link Scalafix} from the provided repositories using Coursier and
-     * classload an instance of it via runtime reflection.
-     * <p>
-     * The custom classloader optionally provided with {@link ScalafixArguments#withToolClasspath} to compile and
-     * classload external rules must have the classloader of the returned instance as ancestor to share a common
-     * loaded instance of `scalafix-core`, and therefore have been compiled against the requested Scala version.
-     *
-     * @param requestedScalaVersion A full Scala version (i.e. "3.3.4") or a major.minor one (i.e. "3.3") to infer
-     *                              the major.minor Scala version that should be available in the classloader of the
-     *                              returned instance. To be able to run advanced semantic rules using the Scala
-     *                              Presentation Compiler such as ExplicitResultTypes, this must be source-compatible
-     *                              with the version that the target classpath is built with, as provided with
-     *                              {@link ScalafixArguments#withScalaVersion}.
-     * @param repositories       Maven/Ivy repositories to fetch the JARs from.
-     * @return An implementation of the {@link Scalafix} interface.
-     * @throws ScalafixException in case of errors during artifact resolution/fetching.
+     * @deprecated Use {@link #get()} instead.
      */
+    @Deprecated
     static Scalafix fetchAndClassloadInstance(String requestedScalaVersion, List<Repository> repositories)
             throws ScalafixException {
 
@@ -164,36 +143,34 @@ static Scalafix fetchAndClassloadInstance(String requestedScalaVersion, List<Rep
     }
 
     /**
-     * JVM runtime reflection method helper to classload an instance of {@link Scalafix}.
-     * <p>
-     * The custom classloader optionally provided with {@link ScalafixArguments#withToolClasspath} to compile and
-     * classload external rules must have the provided classloader as ancestor to share a common loaded instance
-     * of `scalafix-core`, and therefore must have been compiled against the same Scala binary version as
-     * the one in the classLoader provided here.
-     * <p>
-     * Unless you have an advanced use-case, prefer the high-level overloads that cannot cause runtime errors
-     * due to an invalid classloader hierarchy.
-     *
-     * @param classLoader Classloader containing the full Scalafix classpath, including the scalafix-cli module. To be
-     *                    able to run advanced semantic rules using the Scala Presentation Compiler such as
-     *                    ExplicitResultTypes, this Scala binary version in that classloader should match the one that
-     *                    the target classpath was built with, as provided with
-     *                    {@link ScalafixArguments#withScalaVersion}.
-     * @return An implementation of the {@link Scalafix} interface.
-     * @throws ScalafixException in case of errors during classloading, most likely caused
-     *                           by an incorrect classloader argument.
+     * @deprecated Use {@link #get()} instead.
      */
+    @Deprecated
     static Scalafix classloadInstance(ClassLoader classLoader) throws ScalafixException {
         try {
             Class<?> cls = classLoader.loadClass("scalafix.internal.interfaces.ScalafixImpl");
             Constructor<?> ctor = cls.getDeclaredConstructor();
             ctor.setAccessible(true);
             return (Scalafix) ctor.newInstance();
-        } catch (ClassNotFoundException | NoSuchMethodException |
-                IllegalAccessException | InvocationTargetException |
-                InstantiationException ex) {
+        } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException | InvocationTargetException
+                | InstantiationException ex) {
             throw new ScalafixException(
                     "Failed to reflectively load Scalafix with classloader " + classLoader.toString(), ex);
         }
     }
+
+    /**
+     * Obtains an implementation of Scalafix using the current classpath.
+     * 
+     * @return the first available implementation advertised as a service provider.
+     */
+    static Scalafix get() {
+        ServiceLoader<Scalafix> loader = ServiceLoader.load(Scalafix.class);
+        Iterator<Scalafix> iterator = loader.iterator();
+        if (iterator.hasNext()) {
+            return iterator.next();
+        } else {
+            throw new IllegalStateException("No implementation found");
+        }
+    }
 }