fix: reject empty user_input_form items instead of raising IndexError (#37671)

Signed-off-by: Yufeng He <40085740+he-yufeng@users.noreply.github.com>
Co-authored-by: Byron Wang <byron@dify.ai>

api/core/app/app_config/easy_ui_based_app/variables/manager.py

@@ -45,6 +45,8 @@ class BasicVariablesConfigManager:
 
         # variables and external_data_tools
         for variables in config.get("user_input_form", []):
+            if not variables:
+                continue
             variable_type = list(variables.keys())[0]
             if variable_type == VariableEntityType.EXTERNAL_DATA_TOOL:
                 variable = variables[variable_type]
@@ -112,6 +114,8 @@ class BasicVariablesConfigManager:
 
         variables = []
         for item in config["user_input_form"]:
+            if not item:
+                raise ValueError("Each item in user_input_form must be a non-empty object")
             key = list(item.keys())[0]
             # if key not in {"text-input", "select", "paragraph", "number", "external_data_tool"}:
             if key not in {

api/tests/unit_tests/core/app/app_config/easy_ui_based_app/variables/test_manager.py

@@ -70,6 +70,14 @@ class TestBasicVariablesConfigManagerConvert:
         assert len(variables) == 2
         assert len(external) == 1
 
+    def test_convert_empty_form_item_skipped(self):
+        config = {"user_input_form": [{}]}
+
+        variables, external = BasicVariablesConfigManager.convert(config)
+
+        assert variables == []
+        assert external == []
+
     def test_convert_external_data_tool_without_config_skipped(self):
         config = {
             "user_input_form": [
@@ -112,6 +120,12 @@ class TestValidateVariablesAndSetDefaults:
         ):
             BasicVariablesConfigManager.validate_variables_and_set_defaults(config)
 
+    def test_validate_empty_form_item_raises(self):
+        config = {"user_input_form": [{}]}
+
+        with pytest.raises(ValueError, match="Each item in user_input_form must be a non-empty object"):
+            BasicVariablesConfigManager.validate_variables_and_set_defaults(config)
+
     def test_validate_missing_label_raises(self):
         config = {"user_input_form": [{VariableEntityType.TEXT_INPUT: {"variable": "name"}}]}