From 49c628ef1f06e4b4659512964e8c806fe9d9cf12 Mon Sep 17 00:00:00 2001
From: Jaroslav Tulach <jaroslav.tulach@enso.org>
Date: Thu, 5 Dec 2024 11:24:49 +0100
Subject: [PATCH] Propagate Error ASAP instead of ignoring it

---
 CHANGELOG.md                                          |  8 ++++++++
 .../test/semantic/DataflowErrorPropagationTest.java   | 11 ++++++++---
 .../interpreter/node/callable/function/BlockNode.java | 11 ++++++++++-
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9010c33189b1..4dcdceac1a51 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,11 @@
+# Next Next Release
+
+#### Enso Language & Runtime
+
+- [Propagate Error ASAP instead of ignoring it][11777].
+
+[11777]: https://github.com/enso-org/enso/pull/11777
+
 # Next Release
 
 #### Enso IDE
diff --git a/engine/runtime-integration-tests/src/test/java/org/enso/interpreter/test/semantic/DataflowErrorPropagationTest.java b/engine/runtime-integration-tests/src/test/java/org/enso/interpreter/test/semantic/DataflowErrorPropagationTest.java
index 46f466abdb8e..f5facc9d72d1 100644
--- a/engine/runtime-integration-tests/src/test/java/org/enso/interpreter/test/semantic/DataflowErrorPropagationTest.java
+++ b/engine/runtime-integration-tests/src/test/java/org/enso/interpreter/test/semantic/DataflowErrorPropagationTest.java
@@ -7,6 +7,7 @@
 import org.enso.common.MethodNames;
 import org.enso.test.utils.ContextUtils;
 import org.graalvm.polyglot.Context;
+import org.graalvm.polyglot.PolyglotException;
 import org.graalvm.polyglot.Value;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
@@ -59,9 +60,13 @@ public void noErrorReturnValue() {
   @Test
   public void propagateErrorImmediatelly() {
     var value = suppressError.execute(true, 42);
-    assertTrue("It is a number", value.isNumber());
-    assertFalse("Not an error", value.isException());
-    assertEquals(42, value.asInt());
+    assertFalse("It is not a number", value.isNumber());
+    assertTrue("It is an error", value.isException());
+    try {
+      throw value.throwException();
+    } catch (PolyglotException ex) {
+      assertEquals("Yielding an error", ex.getMessage());
+    }
   }
 
   @Test
diff --git a/engine/runtime/src/main/java/org/enso/interpreter/node/callable/function/BlockNode.java b/engine/runtime/src/main/java/org/enso/interpreter/node/callable/function/BlockNode.java
index 994b68b34149..a50ccedbbdbb 100644
--- a/engine/runtime/src/main/java/org/enso/interpreter/node/callable/function/BlockNode.java
+++ b/engine/runtime/src/main/java/org/enso/interpreter/node/callable/function/BlockNode.java
@@ -9,6 +9,8 @@
 import com.oracle.truffle.api.source.SourceSection;
 import java.util.Set;
 import org.enso.interpreter.node.ExpressionNode;
+import org.enso.interpreter.runtime.EnsoContext;
+import org.enso.interpreter.runtime.error.DataflowError;
 
 /**
  * This node defines the body of a function for execution, as well as the protocol for executing the
@@ -55,8 +57,15 @@ public static BlockNode buildSilent(ExpressionNode[] expressions, ExpressionNode
   @Override
   @ExplodeLoop
   public Object executeGeneric(VirtualFrame frame) {
+    var ctx = EnsoContext.get(this);
+    var nothing = ctx.getBuiltins().nothing();
     for (ExpressionNode statement : statements) {
-      statement.executeGeneric(frame);
+      var result = statement.executeGeneric(frame);
+      if (result != nothing) {
+        if (result instanceof DataflowError err) {
+          return err;
+        }
+      }
     }
     return returnExpr.executeGeneric(frame);
   }