Fix modeler.to_file when batch is empty

Author: weiliangjin2021

CHANGELOG.md

@@ -28,6 +28,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 - Make gauge selection for non-converged modes more robust.
 - Fixed extremely long runtime generated by `RunTimeSpec` in the presence of `LossyMetalMedium`.
+- Fixed `ComponentModeler.to_file` when its batch is empty.
 
 ## [2.8.0rc2] - 2025-01-28
 

tests/test_plugins/smatrix/test_component_modeler.py

@@ -381,6 +381,17 @@ def test_import_smatrix_smatrix():
     from tidy3d.plugins.smatrix.smatrix import ComponentModeler, Port  # noqa: F401
 
 
+def test_to_from_file_empty_batch(tmp_path):
+    modeler = make_component_modeler()
+
+    fname = str(tmp_path) + "/modeler.json"
+
+    modeler.to_file(fname)
+    modeler2 = modeler.from_file(fname)
+
+    assert modeler2.batch_cached is None
+
+
 def test_to_from_file_batch(tmp_path, monkeypatch):
     modeler = make_component_modeler()
     _ = run_component_modeler(monkeypatch, modeler)

tidy3d/plugins/smatrix/component_modelers/base.py

@@ -137,14 +137,15 @@ def to_file(self, fname: str) -> None:
         """
 
         batch_cached = self._cached_properties.get("batch")
-        jobs_cached = batch_cached._cached_properties.get("jobs")
-        if jobs_cached is not None:
-            jobs = {}
-            for key, job in jobs_cached.items():
-                task_id = job._cached_properties.get("task_id")
-                jobs[key] = job.updated_copy(task_id_cached=task_id)
-            batch_cached = batch_cached.updated_copy(jobs_cached=jobs)
-        self = self.updated_copy(batch_cached=batch_cached)
+        if batch_cached is not None:
+            jobs_cached = batch_cached._cached_properties.get("jobs")
+            if jobs_cached is not None:
+                jobs = {}
+                for key, job in jobs_cached.items():
+                    task_id = job._cached_properties.get("task_id")
+                    jobs[key] = job.updated_copy(task_id_cached=task_id)
+                batch_cached = batch_cached.updated_copy(jobs_cached=jobs)
+            self = self.updated_copy(batch_cached=batch_cached)
         super(AbstractComponentModeler, self).to_file(fname=fname)  # noqa: UP008
 
     @cached_property