util-eval: Reset reporter between checks

Problem

When you want to use the util-eval for validating the correctness of a small
chunk of code, you have to reset whole state between invocations (flag
resetState=true), which is expensive when you already have a bunch of compiled
and loaded classes. Without this, if one check fails, all subsequent checks
will fail as well, since some errors has been reported previously.

Solution

Scala compiler API allows for resetting just the reporter, so that compiled and
loaded classes can remain for re-usage for next checks.

Result

Public API remains the same, however the internal API has one new synchronized
method resetReporter() which does what is explained in the "Solution" section.

Signed-off-by: Ryan O'Neill <ryano@twitter.com>

RB_ID=859878

2 files changed, 28 insertions, 1 deletions

diff --git a/libraries/eval/Eval.scala b/libraries/eval/Eval.scala
index 92329d3..abd1836 100644
--- a/libraries/eval/Eval.scala
+++ b/libraries/eval/Eval.scala
@@ -242,6 +242,7 @@ class Eval(target: Option[File]) {
     val id = uniqueId(sourceForString(code))
     val className = "Evaluator__" + id
     val wrappedCode = wrapCodeInClass(className, code)
+    resetReporter()
     compile(wrappedCode) // may throw CompilerException
   }
 
@@ -266,6 +267,10 @@ class Eval(target: Option[File]) {
     compiler.findClass(className).getOrElse { throw new ClassNotFoundException("no such class: " + className) }
   }
 
+  private[util] def resetReporter(): Unit = {
+    compiler.resetReporter()
+  }
+
   private[util] def uniqueId(code: String, idOpt: Option[Int] = Some(jvmId)): String = {
     val digest = MessageDigest.getInstance("SHA-1").digest(code.getBytes())
     val sha = new BigInteger(1, digest).toString(16)
@@ -533,6 +538,12 @@ class Eval(target: Option[File]) {
       classLoader = new AbstractFileClassLoader(target, this.getClass.getClassLoader)
     }
 
+    def resetReporter(): Unit = {
+      synchronized {
+        reporter.reset()
+      }
+    }
+
     object Debug {
       val enabled =
         System.getProperty("eval.debug") != null
diff --git a/libraries/eval/test/EvalTest.scala b/libraries/eval/test/EvalTest.scala
index 52913ab..8b986e2 100644
--- a/libraries/eval/test/EvalTest.scala
+++ b/libraries/eval/test/EvalTest.scala
@@ -205,7 +205,7 @@ class EvalTest extends WordSpec {
         assert(eval.errors.nonEmpty)
       }
 
-      "reset reporter between invocations" in {
+      "reset state between invocations" in {
         val ctx = new Ctx
         import ctx._
 
@@ -216,6 +216,22 @@ class EvalTest extends WordSpec {
         assert(eval[Int]("val d = 3; val e = 2; d + e", true) == 5)
         assert(eval.errors.isEmpty)
       }
+
+      "reporter should be reset between checks, but loaded class should remain" in {
+        val ctx = new Ctx
+        import ctx._
+
+        // compile and load compiled class
+        eval.compile("class A()")
+
+        intercept[Throwable] {
+          eval.check("new B()")
+        }
+        assert(eval.errors.nonEmpty)
+
+        eval.check("new A()")
+        assert(eval.errors.isEmpty)
+      }
     }
   }
 }