Promote broken values instead of ignoring them

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

engine/runtime-integration-tests/src/test/java/org/enso/interpreter/test/semantic/DataflowErrorPropagationTest.java

@@ -0,0 +1,86 @@
+package org.enso.interpreter.test.semantic;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+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;
+import org.junit.Test;
+
+public class DataflowErrorPropagationTest {
+  private static Context ctx;
+  private static Value suppressError;
+  private static Value suppressErrorWithAssign;
+
+  @BeforeClass
+  public static void prepareCtx() {
+    ctx = ContextUtils.createDefaultContext();
+    var code =
+        """
+    from Standard.Base import all
+
+    private yield_error yes:Boolean -> Text =
+        if yes then Error.throw "Yielding an error" else
+            "OK"
+
+    suppress_error yes:Boolean value =
+        yield_error yes
+        value
+
+    suppress_error_with_assign yes:Boolean value =
+        _ = yield_error yes
+        value
+    """;
+    suppressError =
+        ctx.eval("enso", code).invokeMember(MethodNames.Module.EVAL_EXPRESSION, "suppress_error");
+    suppressErrorWithAssign =
+        ctx.eval("enso", code)
+            .invokeMember(MethodNames.Module.EVAL_EXPRESSION, "suppress_error_with_assign");
+  }
+
+  @AfterClass
+  public static void disposeCtx() {
+    ctx.close();
+    ctx = null;
+  }
+
+  @Test
+  public void noErrorReturnValue() {
+    var value = suppressError.execute(false, 42);
+    assertTrue("It is a number", value.isNumber());
+    assertEquals(42, value.asInt());
+  }
+
+  @Test
+  public void propagateErrorImmediatelly() {
+    var value = suppressError.execute(true, 42);
+    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
+  public void noErrorReturnValueWithAssign() {
+    var value = suppressErrorWithAssign.execute(false, 42);
+    assertTrue("It is a number", value.isNumber());
+    assertEquals(42, value.asInt());
+  }
+
+  @Test
+  public void errorIsAssignedAndThatIsEnoughReturnValue() {
+    var value = suppressErrorWithAssign.execute(true, 42);
+    assertTrue("It is a number", value.isNumber());
+    assertFalse("Not an error", value.isException());
+    assertEquals(42, value.asInt());
+  }
+}

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);
   }