Cache macro classloader

Author: nicolasstucki

compiler/src/dotty/tools/dotc/Driver.scala

@@ -6,7 +6,7 @@ import dotty.tools.FatalError
 import config.CompilerCommand
 import core.Comments.{ContextDoc, ContextDocstrings}
 import core.Contexts.{Context, ContextBase}
-import core.{Mode, TypeError}
+import core.{MacroClassLoader, Mode, TypeError}
 import reporting._
 
 import scala.util.control.NonFatal
@@ -54,6 +54,7 @@ class Driver {
     val ctx = rootCtx.fresh
     val summary = CompilerCommand.distill(args)(ctx)
     ctx.setSettings(summary.sstate)
+    MacroClassLoader.init(ctx)
 
     if (!ctx.settings.YdropComments.value(ctx) || ctx.mode.is(Mode.ReadComments)) {
       ctx.setProperty(ContextDoc, new ContextDocstrings)

compiler/src/dotty/tools/dotc/core/MacroClassLoader.scala

@@ -0,0 +1,26 @@
+package dotty.tools.dotc.core
+
+import dotty.tools.dotc.core.Contexts._
+import dotty.tools.dotc.util.Property
+import dotty.tools.dotc.reporting.trace
+
+import scala.collection.mutable
+
+object MacroClassLoader {
+
+  /** A key to be used in a context property that caches the class loader used for macro expansion */
+  private val MacroClassLoaderKey = new Property.Key[ClassLoader]
+
+  /** Get the macro class loader */
+  def fromContext(implicit ctx: Context): ClassLoader =
+    ctx.property(MacroClassLoaderKey).getOrElse(makeMacroClassLoader)
+
+  /** Context with a cached macro class loader that can be accessed with `macroClassLoader` */
+  def init(ctx: FreshContext): ctx.type =
+    ctx.setProperty(MacroClassLoaderKey, makeMacroClassLoader(ctx))
+
+  private def makeMacroClassLoader(implicit ctx: Context): ClassLoader = trace("new macro class loader") {
+    val urls = ctx.settings.classpath.value.split(java.io.File.pathSeparatorChar).map(cp => java.nio.file.Paths.get(cp).toUri.toURL)
+    new java.net.URLClassLoader(urls, getClass.getClassLoader)
+  }
+}

compiler/src/dotty/tools/dotc/typer/Inliner.scala

@@ -10,6 +10,7 @@ import Symbols._
 import Types._
 import Decorators._
 import Constants._
+import StagingContext._
 import StdNames._
 import transform.SymUtils._
 import Contexts.Context
@@ -957,20 +958,16 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
       assert(tree.hasType, tree)
       val qual1 = typed(tree.qualifier, selectionProto(tree.name, pt, this))
       val res =
-        if (tree.symbol == defn.QuotedExpr_splice && StagingContext.level == 0) expandMacro(qual1, tree.span)
+        if (tree.symbol == defn.QuotedExpr_splice && level == 0) expandMacro(qual1, tree.span)
         else untpd.cpy.Select(tree)(qual1, tree.name).withType(tree.typeOpt)
       ensureAccessible(res.tpe, tree.qualifier.isInstanceOf[untpd.Super], tree.sourcePos)
       res
     }
 
     private def expandMacro(body: Tree, span: Span)(implicit ctx: Context) = {
-      assert(StagingContext.level == 0)
-      // TODO cache macro classloader
-      val urls = ctx.settings.classpath.value.split(java.io.File.pathSeparatorChar).map(cp => java.nio.file.Paths.get(cp).toUri.toURL)
-      val macroClassLoader = new java.net.URLClassLoader(urls, getClass.getClassLoader)
-
+      assert(level == 0)
       val inlinedFrom = enclosingInlineds.last
-      val evaluatedSplice = Splicer.splice(body, inlinedFrom.sourcePos, macroClassLoader)(ctx.withSource(inlinedFrom.source))
+      val evaluatedSplice = Splicer.splice(body, inlinedFrom.sourcePos, MacroClassLoader.fromContext)(ctx.withSource(inlinedFrom.source))
       if (ctx.reporter.hasErrors) EmptyTree
       else evaluatedSplice.withSpan(span)
     }