Merge pull request #824 from vicmosin/main

feat: I can interrupt an expression evaluation

src/main/scala/org/camunda/feel/impl/interpreter/FeelInterpreter.scala

@@ -39,7 +39,12 @@ import java.time.{Duration, Period}
   */
 class FeelInterpreter {
 
-  def eval(expression: Exp)(implicit context: EvalContext): Val =
+  def eval(expression: Exp)(implicit context: EvalContext): Val = {
+    // Check if the current thread was interrupted, otherwise long-running evaluations can not be interrupted and fully block the thread
+    if (Thread.interrupted()) {
+      throw new InterruptedException()
+    }
+
     expression match {
 
       // literals
@@ -269,6 +274,7 @@ class FeelInterpreter {
       case exp => error(EvaluationFailureType.UNKNOWN, s"Unsupported expression '$exp'")
 
     }
+  }
 
   private def mapEither[T, R](
       it: Iterable[T],

src/test/scala/org/camunda/feel/impl/interpreter/InterpreterInterruptionTest.scala

@@ -0,0 +1,56 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH
+ * under one or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership. Camunda licenses this file to you under the Apache License,
+ * Version 2.0; you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.camunda.feel.impl.interpreter
+
+import org.camunda.feel.impl.FeelEngineTest
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+import java.util.concurrent.{Executors, TimeUnit}
+import concurrent.ExecutionContext
+
+/** @author
+  *   Victor Mosin
+  */
+class InterpreterInterruptionTest extends AnyFlatSpec with Matchers with FeelEngineTest {
+
+  protected implicit val context =
+    ExecutionContext.fromExecutorService(Executors.newSingleThreadExecutor())
+
+  "A long-running evaluation invocation" should "be interrupted after X time" in {
+    val countDownLatch = new java.util.concurrent.CountDownLatch(1)
+    val thread         = new Thread {
+      override def run {
+        try {
+          evaluateExpression(
+            expression = "count(for x in 1..(2 ** 16) return {\"power\": 2 ** x}) > 0"
+          )
+        } catch {
+          case _: InterruptedException =>
+            countDownLatch.countDown()
+        }
+      }
+    }
+
+    thread.start()
+    Thread.sleep(100) // Let evaluation start
+    thread.interrupt()
+    val wasInterrupted = countDownLatch.await(1, TimeUnit.SECONDS)
+
+    wasInterrupted should be(true)
+  }
+}