REPL class loader is context class loader

Author: som-snytt

compiler/src/dotty/tools/repl/ReplDriver.scala

@@ -29,6 +29,7 @@ import dotty.tools.dotc.util.{SourceFile, SourcePosition}
 import dotty.tools.dotc.{CompilationUnit, Driver}
 import dotty.tools.dotc.config.CompilerCommand
 import dotty.tools.io._
+import dotty.tools.runner.ScalaClassLoader.*
 import org.jline.reader._
 
 import scala.annotation.tailrec
@@ -62,7 +63,7 @@ case class State(objectIndex: Int,
 /** Main REPL instance, orchestrating input, compilation and presentation */
 class ReplDriver(settings: Array[String],
                  out: PrintStream = Console.out,
-                 classLoader: Option[ClassLoader] = None) extends Driver {
+                 classLoader: Option[ClassLoader] = None) extends Driver:
 
   /** Overridden to `false` in order to not have to give sources on the
    *  commandline
@@ -161,15 +162,17 @@ class ReplDriver(settings: Array[String],
       else loop(interpret(res)(state))
     }
 
-    try withRedirectedOutput { loop(initialState) }
+    try runBody { loop(initialState) }
     finally terminal.close()
   }
 
-  final def run(input: String)(implicit state: State): State = withRedirectedOutput {
+  final def run(input: String)(implicit state: State): State = runBody {
     val parsed = ParseResult(input)(state)
     interpret(parsed)
   }
 
+  private def runBody(body: => State): State = rendering.classLoader()(using rootCtx).asContext(withRedirectedOutput(body))
+
   // TODO: i5069
   final def bind(name: String, value: Any)(implicit state: State): State = state
 
@@ -455,4 +458,5 @@ class ReplDriver(settings: Array[String],
   private def printDiagnostic(dia: Diagnostic)(implicit state: State) = dia.level match
     case interfaces.Diagnostic.INFO => out.println(dia.msg) // print REPL's special info diagnostics directly to out
     case _                          => ReplConsoleReporter.doReport(dia)(using state.context)
-}
+
+end ReplDriver

compiler/src/dotty/tools/runner/ScalaClassLoader.scala

@@ -14,12 +14,8 @@ import scala.annotation.tailrec
 import scala.util.control.Exception.catching
 
 final class RichClassLoader(private val self: ClassLoader) extends AnyVal {
-  /** Executing an action with this classloader as context classloader */
-  private def asContext[T](action: => T): T = {
-    val saved = Thread.currentThread.getContextClassLoader
-    try { ScalaClassLoader.setContext(self) ; action }
-    finally ScalaClassLoader.setContext(saved)
-  }
+  /** Execute an action with this classloader as context classloader. */
+  private def asContext[T](action: => T): T = ScalaClassLoader.asContext(self)(action)
 
   /** Load and link a class with this classloader */
   def tryToLoadClass[T <: AnyRef](path: String): Option[Class[T]] = tryClass(path, initialize = false)
@@ -74,4 +70,13 @@ object ScalaClassLoader {
         MethodHandles.lookup().findStatic(classOf[ClassLoader], "getPlatformClassLoader", MethodType.methodType(classOf[ClassLoader])).invoke().asInstanceOf[ClassLoader]
       catch case _: Throwable => null
     else null
+
+  extension (classLoader: ClassLoader)
+    /** Execute an action with this classloader as context classloader. */
+    def asContext[T](action: => T): T =
+      val saved = Thread.currentThread.getContextClassLoader
+      try
+        setContext(classLoader)
+        action
+      finally setContext(saved)
 }

compiler/test/dotty/tools/repl/ReplCompilerTests.scala

@@ -241,6 +241,10 @@ class ReplCompilerTests extends ReplTest {
       ... 28 elided
      */
   }
+  @Test def `i14281 context class loader must be REPL class loader` = fromInitialState { implicit state =>
+    run("class C ; assert(classOf[C].getClassLoader eq Thread.currentThread.getContextClassLoader)")
+    assertEquals(List("// defined class C"), lines())
+  }
 }
 
 object ReplCompilerTests {