fix(core): WorkingDirectory validation throws an exception when tasks…

… is null or empty

core/src/main/java/io/kestra/core/validations/ValidationFactory.java

@@ -160,7 +160,12 @@ ConstraintValidator<WorkingDirectoryTaskValidation, WorkingDirectory> workingDir
                 return true;
             }
 
-            if(value.getTasks().stream().anyMatch(task -> !(task instanceof RunnableTask<?>))) {
+            if (value.getTasks() == null || value.getTasks().isEmpty()) {
+                context.messageTemplate("The 'tasks' property cannot be empty");
+                return false;
+            }
+
+            if (value.getTasks().stream().anyMatch(task -> !(task instanceof RunnableTask<?>))) {
                 context.messageTemplate("Only runnable tasks are allowed as children of a WorkingDirectory task");
                 return false;
             }

core/src/test/java/io/kestra/core/models/flows/FlowTest.java

@@ -95,6 +95,17 @@ void workingDirectoryTaskInvalid() {
         assertThat(validate.get().getMessage(), containsString("tasks[0]: Only runnable tasks are allowed as children of a WorkingDirectory task"));
     }
 
+    @Test
+    void workingDirectoryNoTasks() {
+        Flow flow = this.parse("flows/invalids/workingdirectory-no-tasks.yaml");
+        Optional<ConstraintViolationException> validate = modelValidator.isValid(flow);
+
+        assertThat(validate.isPresent(), is(true));
+        assertThat(validate.get().getConstraintViolations().size(), is(2));
+
+        assertThat(validate.get().getMessage(), containsString("tasks[0]: The tasks property cannot be empty"));
+    }
+
     @Test
     void updateTask() throws InternalException {
         Flow flow = this.parse("flows/valids/each-sequential-nested.yaml");

core/src/test/resources/flows/invalids/workingdirectory-no-tasks.yaml

@@ -0,0 +1,6 @@
+id: workingdirectory-no-tasks
+namespace: io.kestra.tests
+
+tasks:
+  - id: impossible
+    type: io.kestra.core.tasks.flows.WorkingDirectory