Force the returned value in test.catch() and test.catchOrNull() (#1910)

pkl-core/src/main/java/org/pkl/core/stdlib/test/TestNodes.java

@@ -39,7 +39,7 @@ public final class TestNodes {
     @Specialization
     protected String eval(@SuppressWarnings("unused") VmTyped self, VmFunction function) {
       try {
-        applyLambdaNode.execute(function);
+        VmValue.force(applyLambdaNode.execute(function), false);
       } catch (VmException e) {
         return render(e);
       }
@@ -54,7 +54,7 @@ public final class TestNodes {
     @Specialization
     protected Object eval(@SuppressWarnings("unused") VmTyped self, VmFunction function) {
       try {
-        applyLambdaNode.execute(function);
+        VmValue.force(applyLambdaNode.execute(function), false);
       } catch (VmException e) {
         return render(e);
       }

pkl-core/src/test/files/LanguageSnippetTests/input/api/testModule.pkl

@@ -0,0 +1,19 @@
+amends "../snippetTest.pkl"
+
+import "pkl:test"
+
+examples {
+  ["catch"] {
+    test.catch(() -> throw("ouch"))
+    // the returned value is fully evaluated, so these are caught too
+    test.catch(() -> new Listing { 1 } as Listing<String>)
+    test.catch(() -> new Dynamic { foo { bar = throw("nested") } })
+  }
+  ["catchOrNull"] {
+    test.catchOrNull(() -> 42)
+    test.catchOrNull(() -> throw("ouch"))
+    // the returned value is fully evaluated, so these are caught too
+    test.catchOrNull(() -> new Listing { 1 } as Listing<String>)
+    test.catchOrNull(() -> new Dynamic { foo { bar = throw("nested") } })
+  }
+}

pkl-core/src/test/files/LanguageSnippetTests/output/api/testModule.pcf

@@ -0,0 +1,13 @@
+examples {
+  ["catch"] {
+    "ouch"
+    "Expected value of type `String`, but got type `Int`. Value: 1"
+    "nested"
+  }
+  ["catchOrNull"] {
+    null
+    "ouch"
+    "Expected value of type `String`, but got type `Int`. Value: 1"
+    "nested"
+  }
+}

pkl-core/src/test/files/LanguageSnippetTests/output/basic/as3.pcf

@@ -5,11 +5,11 @@ examples {
     "Expected value of type `Int`, but got type `String`. Value: \"one\""
   }
   ["listing"] {
-    true
+    false
     "Expected value of type `String`, but got type `Int`. Value: 1"
   }
   ["mapping"] {
-    true
+    false
     "Expected value of type `String`, but got type `Int`. Value: 1"
     "Expected value of type `String`, but got type `Int`. Value: 2"
     "Expected value of type `Int`, but got type `String`. Value: \"hi\""

stdlib/test.pkl

@@ -88,10 +88,14 @@ examples: Mapping<String, Listing<unknown>>?
 
 /// Applies [fun] and returns the error thrown.
 ///
+/// The value returned by [fun] is fully evaluated, so an error inside a nested object member will be caught too.
+///
 /// Throws if [fun] did not throw an error.
 external const function catch(fun: () -> Any): String
 
 /// Applies [fun] and returns the error thrown.
 ///
+/// The value returned by [fun] is fully evaluated, so an error inside a nested object member will be caught too.
+///
 /// Returns [null] if [fun] did not throw an error.
 external const function catchOrNull(fun: () -> Any): String?