Avoid WithWarnings without any warnings (#8583)

engine/runtime/src/main/java/org/enso/interpreter/node/expression/builtin/ordering/SortVectorNode.java

@@ -263,7 +263,10 @@ public abstract class SortVectorNode extends Node {
         }
         case REPORT_WARNING -> {
           return attachDifferentComparatorsWarning(
-              attachWarnings(sortedVector, gatheredWarnings), groups);
+              gatheredWarnings.isEmpty()
+                  ? sortedVector
+                  : attachWarnings(sortedVector, gatheredWarnings),
+              groups);
         }
         case IGNORE -> {
           return sortedVector;

engine/runtime/src/main/java/org/enso/interpreter/runtime/error/WithWarnings.java

@@ -35,11 +35,12 @@ public final class WithWarnings implements EnsoObject {
    * @param maxWarnings maximal number of warnings allowed to be attached to the value
    * @param limitReached if `true`, indicates that `warnings` have already been limited for a
    *     custom-method, `false` otherwise
-   * @param warnings warnings to be attached to a value
+   * @param warnings non-empty warnings to be attached to a value
    */
   private WithWarnings(Object value, int maxWarnings, boolean limitReached, Warning... warnings) {
     assert !(value instanceof WithWarnings);
     this.warnings = createSetFromArray(maxWarnings, warnings);
+    assert this.warnings.size() > 0;
     this.value = value;
     this.limitReached = limitReached || this.warnings.size() >= maxWarnings;
     this.maxWarnings = maxWarnings;
@@ -69,6 +70,7 @@ public final class WithWarnings implements EnsoObject {
       Warning... additionalWarnings) {
     assert !(value instanceof WithWarnings);
     this.warnings = cloneSetAndAppend(maxWarnings, warnings, additionalWarnings);
+    assert this.warnings.size() > 0;
     this.value = value;
     this.limitReached = limitReached || this.warnings.size() >= maxWarnings;
     this.maxWarnings = maxWarnings;
@@ -168,7 +170,7 @@ public final class WithWarnings implements EnsoObject {
 
   @ExportMessage
   boolean hasWarnings() {
-    return warnings.size() > 0;
+    return true;
   }
 
   @ExportMessage

engine/runtime/src/test/java/org/enso/interpreter/test/WarningsTest.java

@@ -1,6 +1,7 @@
 package org.enso.interpreter.test;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
 
 import org.enso.interpreter.runtime.EnsoContext;
 import org.enso.interpreter.runtime.error.Warning;
@@ -17,24 +18,26 @@ import org.junit.Test;
 public class WarningsTest extends TestBase {
 
   private static Context ctx;
+  private static EnsoContext ensoContext;
 
   @BeforeClass
   public static void initEnsoContext() {
     ctx = createDefaultContext();
+    ensoContext =
+        (EnsoContext)
+            ctx.getBindings(LanguageInfo.ID)
+                .invokeMember(MethodNames.TopScope.LEAK_CONTEXT)
+                .asHostObject();
   }
 
   @AfterClass
   public static void disposeContext() {
+    ensoContext = null;
     ctx.close();
   }
 
   @Test
   public void doubleWithWarningsWrap() {
-    var ensoContext =
-        (EnsoContext)
-            ctx.getBindings(LanguageInfo.ID)
-                .invokeMember(MethodNames.TopScope.LEAK_CONTEXT)
-                .asHostObject();
     var warn1 = Warning.create(ensoContext, "w1", this);
     var warn2 = Warning.create(ensoContext, "w2", this);
     var value = 42;
@@ -49,4 +52,17 @@ public class WarningsTest extends TestBase {
     Assert.assertArrayEquals(
         new Object[] {warn1, warn2}, with2.getWarningsArray(WarningsLibrary.getUncached()));
   }
+
+  @Test
+  public void wrapAndUnwrap() {
+    var value = 42;
+    WithWarnings without;
+    try {
+      without = WithWarnings.wrap(ensoContext, 42, new Warning[0]);
+    } catch (AssertionError e) {
+      // OK
+      return;
+    }
+    fail("One shall not be created WithWarnings without any warnings " + without);
+  }
 }