Improve handling of exceptions in script execution #12

Author: jpsacha

scala-console/src/main/scala-3/dotty/tools/repl/SCIMain.scala

@@ -4,10 +4,13 @@ import dotty.tools.dotc.core.StdNames.str
 
 import java.io.PrintStream
 import java.lang.reflect.Method
+import scala.annotation.tailrec
 import scala.util.control.NonFatal
+import scala.util.{Failure, Success, Try}
 
 /** Interprets Scala code, based on `dotty.tools.repl.ScriptEngine` */
 class SCIMain(out: PrintStream, loader: ClassLoader) {
+  import SCIMain.*
 
   private val driver =
     new ReplDriver(
@@ -21,32 +24,41 @@ class SCIMain(out: PrintStream, loader: ClassLoader) {
       out,
       Some(loader)
     )
-
-  private var state     = driver.initialState
   private val rendering = new Rendering(Some(getClass.getClassLoader))
+  private var state     = driver.initialState
 
   def bind(tup: (String, Any)): Unit =
     state = driver.bind(tup._1, tup._2)(using state)
 
   def interpret(line: String): SCResults = {
-    val methodOpt: Option[Method] =
-      try {
+    // Parse script
+    val methodTry: Try[Option[Method]] =
+      Try {
         evalToMethod(line)
-      } catch {
-        case NonFatal(ex) =>
-//          ex.printStackTrace()
-//          ex.printStackTrace(out)
-          return SCResults.Error
       }
 
-    val valueOpt: Option[Any] = methodOpt.map(_.invoke(null))
+    // Execute parsed script
+    val result: Try[Unit] =
+      for methodOpt <- methodTry yield {
+        for method <- methodOpt do
+          val value = method.invoke(null)
+          if value != () then
+            out.println(s"${method.getName}: $value")
+      }
+
+    // Interpret script execution result
+    result match
+      case Success(_) =>
+        SCResults.Success
+      case Failure(ex) =>
+        if wasCausedByImageJMacroAbort(ex) then
+          out.println(s"WARNING: Detected ImageJ's \"$IMAGEJ_MACRO_CANCELED\" request. Stopping script execution.")
+          SCResults.Success
+        else
+          // ex.printStackTrace()
+          // ex.printStackTrace(out)
+          SCResults.Error
 
-    val value      = valueOpt.getOrElse(())
-    val methodName = methodOpt.fold("")(_.getName)
-    if (methodOpt.isDefined && valueOpt.isDefined && !valueOpt.contains(())) {
-      out.println(s"$methodName: $value")
-    }
-    SCResults.Success
   }
 
   private def evalToMethod(script: String): Option[Method] = {
@@ -59,4 +71,23 @@ class SCIMain(out: PrintStream, loader: ClassLoader) {
       .find(_.getName == s"${str.REPL_RES_PREFIX}$vid")
   }
 
+  /**
+   * Check if exception has a signature of an exception thrown by ImageJ to indicate that macro cancellation.
+   * @param t exception to test
+   * @return `true` is the exception matches the ImageJ' macro abort exception.
+   */
+  @tailrec
+  private final def wasCausedByImageJMacroAbort(t: Throwable): Boolean = {
+    if t == null then
+      false
+    else if t.isInstanceOf[RuntimeException] & t.getMessage == IMAGEJ_MACRO_CANCELED then
+      true
+    else
+      wasCausedByImageJMacroAbort(t.getCause)
+  }
+
 }
+
+object SCIMain:
+  private val IMAGEJ_MACRO_CANCELED = "Macro canceled"
+end SCIMain