fix(ui): omit empty schema params so eval-backed defaults resolve (#2173)

Author: kriyanshii

ui/src/features/dags/components/dag-execution/__tests__/paramSchemaForm.test.ts

@@ -95,4 +95,14 @@ describe('paramSchemaForm helpers', () => {
       })
     ).toBe('{"region":"us-west-2","count":5,"debug":false}');
   });
+
+  it('omits empty string and null values so eval-backed params are not overridden', () => {
+    expect(
+      stringifyParamSchemaFormData({
+        sharedWorkDir: '',
+        region: 'us-east-1',
+        optional: null,
+      } as ParamSchemaFormData)
+    ).toBe('{"region":"us-east-1"}');
+  });
 });

ui/src/features/dags/components/dag-execution/paramSchemaForm.ts

@@ -65,11 +65,20 @@ export function buildParamSchemaUiSchema(
 
 /**
  * Serializes schema form data into the parameter payload expected by the start API.
+ * Empty strings and nulls are omitted so the backend does not treat them as explicit
+ * overrides (which would skip eval-backed parameters). See dagucloud/dagu#2032.
  */
 export function stringifyParamSchemaFormData(
   formData: ParamSchemaFormData
 ): string {
-  return JSON.stringify(formData);
+  const filtered: ParamSchemaFormData = {};
+  for (const [key, value] of Object.entries(formData)) {
+    if (value === '' || value === null) {
+      continue;
+    }
+    filtered[key] = value;
+  }
+  return JSON.stringify(filtered);
 }
 
 /**