Fix for file names containing dots

Signed-off-by: Lucas Heitzmann Gabrielli <lucas@flexcompute.com>

CHANGELOG.md

@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Proper equality checking between `Tidy3dBaseModel` instances, which takes `DataArray` values and coords into account and handles `np.ndarray` types.
 - Correctly set the contour length scale when exporting 2D (or 1D) structures with custom medium to GDSII.
 - Improved error handling if file can not be downloaded from server.
+- Fix for detection of file extensions for file names with dots.
 
 ## [2.5.0rc2] - 2023-10-30
 

tidy3d/components/base.py

@@ -68,13 +68,20 @@ def ndarray_encoder(val):
 
 def _get_valid_extension(fname: str) -> str:
     """Return the file extension from fname, validated to accepted ones."""
-    extension = "".join(pathlib.Path(fname).suffixes).lower()
-    valid_extensions = [".json", ".yaml", ".hdf5", ".hdf5.gz", ".h5"]
-    if extension not in valid_extensions:
-        raise FileError(
-            f"{fname}::File extension must be in {valid_extensions}, but '{extension}' given"
-        )
-    return extension
+    valid_extensions = [".json", ".yaml", ".hdf5", ".h5", ".hdf5.gz"]
+    extensions = [s.lower() for s in pathlib.Path(fname).suffixes[-2:]]
+    if len(extensions) == 0:
+        raise FileError(f"File '{fname}' missing extension.")
+    single_extension = extensions[-1]
+    if single_extension in valid_extensions:
+        return single_extension
+    double_extension = "".join(extensions)
+    if double_extension in valid_extensions:
+        return double_extension
+    raise FileError(
+        f"File extension must be one of {', '.join(valid_extensions)}; file '{fname}' does not "
+        "match any of those."
+    )
 
 
 class Tidy3dBaseModel(pydantic.BaseModel):