Add fsspec support to li_l2_nc reader

satpy/etc/readers/generic_image.yaml

@@ -4,7 +4,7 @@ reader:
     long_name: Generic Images e.g. GeoTIFF
     description: generic image reader
     status: Nominal
-    supports_fsspec: false
+    supports_fsspec: true
     reader: !!python/name:satpy.readers.yaml_reader.FileYAMLReader
     sensors: [images]
     default_channels: [image]

satpy/readers/li_base_nc.py

@@ -191,12 +191,12 @@
 import xarray as xr
 from pyproj import Proj
 
-from satpy.readers.netcdf_utils import NetCDF4FileHandler
+from satpy.readers.netcdf_utils import NetCDF4FsspecFileHandler
 
 logger = logging.getLogger(__name__)
 
 
-class LINCFileHandler(NetCDF4FileHandler):
+class LINCFileHandler(NetCDF4FsspecFileHandler):
     """Base class used as parent for the concrete LI reader classes."""
 
     def __init__(self, filename, filename_info, filetype_info, cache_handle=True):

satpy/readers/netcdf_utils.py

@@ -258,13 +258,7 @@ def collect_cache_vars(self, cache_var_size):
         cache_vars = self._collect_cache_var_names(cache_var_size)
         for var_name in cache_vars:
             v = self.file_content[var_name]
-            try:
-                arr = xr.DataArray(
-                    v[:], dims=v.dimensions, attrs=v.__dict__, name=v.name)
-            except ValueError:
-                # Handle scalars for h5netcdf backend
-                arr = xr.DataArray(
-                    v.__array__(), dims=v.dimensions, attrs=v.__dict__, name=v.name)
+            arr = get_data_as_xarray(v)
             self.cached_file_content[var_name] = arr
 
     def _collect_cache_var_names(self, cache_var_size):
@@ -380,6 +374,24 @@ def _compose_replacement_names(variable_name_replacements, var, variable_names):
                 variable_names.append(var.format(**{key: val}))
 
 
+def get_data_as_xarray(variable):
+    """Get data in variable as xr.DataArray."""
+    try:
+        attrs = variable.attrs
+    except AttributeError:
+        # netCDF4 backend requires usage of __dict__ to get the attributes
+        attrs = variable.__dict__
+    try:
+        data = variable[:]
+    except (ValueError, IndexError):
+        # Handle scalars for h5netcdf backend
+        data = variable.__array__()
+
+    arr = xr.DataArray(data, dims=variable.dimensions, attrs=attrs, name=variable.name)
+
+    return arr
+
+
 class NetCDF4FsspecFileHandler(NetCDF4FileHandler):
     """NetCDF4 file handler using fsspec to read files remotely."""
 

satpy/tests/reader_tests/test_netcdf_utils.py

@@ -293,3 +293,102 @@
                 fh = NetCDF4FsspecFileHandler(fname, {}, {})
                 h5_file.assert_called_once()
                 assert fh._use_h5netcdf
+
+
+NC_ATTRS = {
+    "standard_name": "test_data",
+    "scale_factor": 0.01,
+    "add_offset": 0}
+
+def test_get_data_as_xarray_netcdf4(tmp_path):
+    """Test getting xr.DataArray from netcdf4 variable."""
+    import numpy as np
+
+    from satpy.readers.netcdf_utils import get_data_as_xarray
+
+    data = np.array([1, 2, 3])
+    fname = tmp_path / "test.nc"
+    dset = _write_test_netcdf4(fname, data)
+
+    res = get_data_as_xarray(dset["test_data"])
+    np.testing.assert_equal(res.data, data)
+    assert res.attrs == NC_ATTRS
+
+
+def test_get_data_as_xarray_scalar_netcdf4(tmp_path):
+    """Test getting scalar xr.DataArray from netcdf4 variable."""
+    import numpy as np
+
+    from satpy.readers.netcdf_utils import get_data_as_xarray
+
+    data = 1
+    fname = tmp_path / "test.nc"
+    dset = _write_test_netcdf4(fname, data)
+
+    res = get_data_as_xarray(dset["test_data"])
+    np.testing.assert_equal(res.data, np.array(data))
+    assert res.attrs == NC_ATTRS
+
+
+def _write_test_netcdf4(fname, data):
+    import netCDF4 as nc
+
+    dset = nc.Dataset(fname, "w")
+    try:
+        dset.createDimension("y", data.size)
+        dims = ("y",)
+    except AttributeError:
+        dims = ()
+    var = dset.createVariable("test_data", "uint8", dims)
+    var[:] = data
+    var.setncatts(NC_ATTRS)
+    # Turn off automatic scale factor and offset handling
+    dset.set_auto_maskandscale(False)
+
+    return dset
+
+
+def test_get_data_as_xarray_h5netcdf(tmp_path):
+    """Test getting xr.DataArray from h5netcdf variable."""
+    import numpy as np
+
+    from satpy.readers.netcdf_utils import get_data_as_xarray
+
+    data = np.array([1, 2, 3])
+    fname = tmp_path / "test.nc"
+    fid = _write_test_h5netcdf(fname, data)
+
+    res = get_data_as_xarray(fid["test_data"])
+    np.testing.assert_equal(res.data, data)
+    assert res.attrs == NC_ATTRS
+
+
+def _write_test_h5netcdf(fname, data):
+    import h5netcdf
+
+    fid = h5netcdf.File(fname, "w")
+    try:
+        fid.dimensions = {"y": data.size}
+        dims = ("y",)
+    except AttributeError:
+        dims = ()
+    var = fid.create_variable("test_data", dims, "uint8", data=data)
+    for key in NC_ATTRS:
+        var.attrs[key] = NC_ATTRS[key]
+
+    return fid
+
+
+def test_get_data_as_xarray_scalar_h5netcdf(tmp_path):
+    """Test getting xr.DataArray from h5netcdf variable."""
+    import numpy as np
+
+    from satpy.readers.netcdf_utils import get_data_as_xarray
+
+    data = 1
+    fname = tmp_path / "test.nc"
+    fid = _write_test_h5netcdf(fname, data)
+
+    res = get_data_as_xarray(fid["test_data"])
+    np.testing.assert_equal(res.data, np.array(data))
+    assert res.attrs == NC_ATTRS