Convert user defined filetype to FileType (#79)

* convert ud filetype to FileType

* added test for FileType

virtualizarr/kerchunk.py

@@ -52,6 +52,9 @@ def read_kerchunk_references_from_file(
     if filetype is None:
         filetype = _automatically_determine_filetype(filepath)
 
+    # if filetype is user defined, convert to FileType
+    filetype = FileType(filetype)
+
     if filetype.name.lower() == "netcdf3":
         from kerchunk.netCDF3 import NetCDF3ToZarr
         refs = NetCDF3ToZarr(filepath, inline_threshold=0).translate()

virtualizarr/tests/test_kerchunk.py

@@ -2,6 +2,8 @@
 import ujson  # type: ignore
 import xarray as xr
 import xarray.testing as xrt
+import pytest
+
 
 from virtualizarr.kerchunk import _automatically_determine_filetype, FileType
 from virtualizarr.manifests import ChunkEntry, ChunkManifest, ManifestArray
@@ -158,3 +160,17 @@ def test_automatically_determine_filetype_netcdf3_netcdf4():
     ds.to_netcdf(netcdf4_file_path)
     assert FileType("netcdf3") == _automatically_determine_filetype(netcdf3_file_path)
     assert FileType("netcdf4") == _automatically_determine_filetype(netcdf4_file_path)
+
+
+
+
+def test_FileType():
+    # tests if FileType converts user supplied strings to correct filetype
+    assert 'netcdf3' == FileType("netcdf3").name
+    assert 'netcdf4' == FileType("netcdf4").name
+    assert 'grib' == FileType("grib").name
+    assert 'tiff' == FileType("tiff").name
+    assert 'fits' == FileType("fits").name
+    assert 'zarr' == FileType("zarr").name
+    with pytest.raises(ValueError):
+        FileType(None)