Return null rather than throwing exception when conversion fail (#1222)

Signed-off-by: fjtirado <ftirados@redhat.com>

Author: fjtirado

experimental/lambda/src/main/java/io/serverlessworkflow/impl/expressions/func/JavaExpressionFactory.java

@@ -25,6 +25,7 @@
 import io.serverlessworkflow.api.types.func.TypedJavaContextFunction;
 import io.serverlessworkflow.api.types.func.TypedJavaFilterFunction;
 import io.serverlessworkflow.api.types.func.TypedPredicate;
+import io.serverlessworkflow.impl.WorkflowModel;
 import io.serverlessworkflow.impl.WorkflowPredicate;
 import io.serverlessworkflow.impl.expressions.AbstractExpressionFactory;
 import io.serverlessworkflow.impl.expressions.ExpressionDescriptor;
@@ -44,20 +45,31 @@ public ObjectExpression buildExpression(ExpressionDescriptor descriptor) {
     if (value instanceof Function func) {
       return (w, t, n) -> func.apply(n.asJavaObject());
     } else if (value instanceof TypedFunction func) {
-      return (w, t, n) -> func.function().apply(n.as(func.argClass()).orElseThrow());
+      return (w, t, n) -> func.function().apply(convert(n, func.argClass()));
     } else if (value instanceof JavaFilterFunction func) {
       return (w, t, n) -> func.apply(n.asJavaObject(), w, t);
     } else if (value instanceof TypedJavaFilterFunction func) {
-      return (w, t, n) -> func.function().apply(n.as(func.argClass()).orElseThrow(), w, t);
+      return (w, t, n) -> func.function().apply(convert(n, func.argClass()), w, t);
     } else if (value instanceof JavaContextFunction func) {
       return (w, t, n) -> func.apply(n.asJavaObject(), w);
     } else if (value instanceof TypedJavaContextFunction func) {
-      return (w, t, n) -> func.function().apply(n.as(func.argClass()).orElseThrow(), w);
+      return (w, t, n) -> func.function().apply(convert(n, func.argClass()), w);
     } else {
       return (w, t, n) -> value;
     }
   }
 
+  private <T> T convert(WorkflowModel model, Class<T> argClass) {
+    return model.isNull()
+        ? null
+        : model
+            .as(argClass)
+            .orElseThrow(
+                () ->
+                    new IllegalArgumentException(
+                        "Cannot convert model " + model.asJavaObject() + " to class" + argClass));
+  }
+
   @Override
   public int priority(ExpressionDescriptor descriptor) {
     Object value = descriptor.asObject();

experimental/lambda/src/test/java/io/serverless/workflow/impl/executors/func/FuncDSLDataFlowTransformationHelpersTest.java

@@ -122,7 +122,8 @@ void test_output_with_exportAs() {
                           Long taskOutput = output(taskContextData, Long.class);
                           softly.assertThat(taskOutput).isEqualTo(15L);
                           return taskOutput * 2;
-                        }))
+                        },
+                        Object.class))
             .build();
 
     try (WorkflowApplication app = WorkflowApplication.builder().build()) {

impl/core/src/main/java/io/serverlessworkflow/impl/WorkflowModel.java

@@ -39,4 +39,8 @@ public interface WorkflowModel {
   Class<?> objectClass();
 
   <T> Optional<T> as(Class<T> clazz);
+
+  default boolean isNull() {
+    return asJavaObject() == null;
+  }
 }

impl/model/src/main/java/io/serverlessworkflow/impl/model/jackson/JacksonModel.java

@@ -46,6 +46,11 @@ protected JacksonModel(JsonNode node) {
     this.node = node;
   }
 
+  @Override
+  public boolean isNull() {
+    return node.isNull();
+  }
+
   @Override
   public Optional<Boolean> asBoolean() {
     return node.isBoolean() ? Optional.of(node.asBoolean()) : Optional.empty();