xarray.to_netcdf kwargs and tests

CHANGELOG.rst

@@ -5,7 +5,8 @@ Changelog for cfgrib
 0.9.10.2 (unreleased)
 ---------------------
 
-- Nothing changed yet.
+- added --netcdf_kwargs_json option to 'cfgrib to_netcdf'
+  See `#294 <https://github.com/ecmwf/cfgrib/pull/294/>`_.
 
 
 0.9.10.1 (2022-03-16)

cfgrib/__main__.py

@@ -17,6 +17,7 @@
 #   Alessandro Amici - B-Open - https://bopen.eu
 #
 
+import json
 import os.path
 import typing as T
 
@@ -25,6 +26,21 @@
 # NOTE: imports are executed inside functions so missing dependencies don't break all commands
 
 
+def handle_json(in_json):
+    """
+    Handle input json which can be a a json format string, or path to a json format file.
+    Returns a dictionary of the json contents.
+    """
+    try:
+        # Assume a json format string
+        out_json = json.loads(in_json)
+    except json.JSONDecodeError:
+        # Then a json file
+        with open(in_json, "r") as f:
+            out_json = json.load(f)
+    return out_json
+
+
 @click.group()
 def cfgrib_cli() -> None:
     pass
@@ -57,10 +73,18 @@ def selfcheck() -> None:
         "the path to JSON file"
     ),
 )
-def to_netcdf(inpaths, outpath, cdm, engine, backend_kwargs_json):
-    # type: (T.List[str], str, str, str, str) -> None
-    import json
-
+@click.option(
+    "--netcdf-kwargs-json",
+    "-n",
+    default=None,
+    help=(
+        "kwargs used xarray.to_netcdf when creating the netCDF file."
+        "Can either be a JSON format string or "
+        "the path to JSON file."
+    ),
+)
+def to_netcdf(inpaths, outpath, cdm, engine, backend_kwargs_json, netcdf_kwargs_json):
+    # type: (T.List[str], str, str, str, str, str) -> None
     import xarray as xr
 
     import cf2cdm
@@ -73,13 +97,7 @@ def to_netcdf(inpaths, outpath, cdm, engine, backend_kwargs_json):
         outpath = os.path.splitext(inpaths[0])[0] + ".nc"
 
     if backend_kwargs_json is not None:
-        try:
-            # Assume a json format string
-            backend_kwargs = json.loads(backend_kwargs_json)
-        except json.JSONDecodeError:
-            # Then a json file
-            with open(backend_kwargs_json, "r") as f:
-                backend_kwargs = json.load(f)
+        backend_kwargs = handle_json(backend_kwargs_json)
     else:
         backend_kwargs = {}
 
@@ -97,7 +115,12 @@ def to_netcdf(inpaths, outpath, cdm, engine, backend_kwargs_json):
         coord_model = getattr(cf2cdm, cdm)
         ds = cf2cdm.translate_coords(ds, coord_model=coord_model)
 
-    ds.to_netcdf(outpath)
+    if netcdf_kwargs_json is not None:
+        netcdf_kwargs = handle_json(netcdf_kwargs_json)
+    else:
+        netcdf_kwargs = {}
+
+    ds.to_netcdf(outpath, **netcdf_kwargs)
 
 
 @cfgrib_cli.command("dump")

tests/test_60_main_commands.py

@@ -32,6 +32,10 @@ def test_cfgrib_cli_to_netcdf(tmpdir: py.path.local) -> None:
     assert res.exit_code == 0
     assert res.output == ""
 
+
+def test_cfgrib_cli_to_netcdf_backend_kwargs(tmpdir: py.path.local) -> None:
+    runner = click.testing.CliRunner()
+
     backend_kwargs = '{"time_dims": ["time"]}'
     res = runner.invoke(__main__.cfgrib_cli, ["to_netcdf", TEST_DATA, "-b", backend_kwargs])
 
@@ -49,6 +53,26 @@ def test_cfgrib_cli_to_netcdf(tmpdir: py.path.local) -> None:
     assert res.output == ""
 
 
+def test_cfgrib_cli_to_netcdf_netcdf_kwargs(tmpdir: py.path.local) -> None:
+    runner = click.testing.CliRunner()
+
+    netcdf_kwargs = '{"engine": "scipy"}'
+    res = runner.invoke(__main__.cfgrib_cli, ["to_netcdf", TEST_DATA, "-n", netcdf_kwargs])
+
+    assert res.exit_code == 0
+    assert res.output == ""
+
+    netcdf_kwargs_json = tmpdir.join("temp.json")
+    with open(netcdf_kwargs_json, "w") as f:
+        f.write(netcdf_kwargs)
+    res = runner.invoke(
+        __main__.cfgrib_cli, ["to_netcdf", TEST_DATA, "-n", str(netcdf_kwargs_json)]
+    )
+
+    assert res.exit_code == 0
+    assert res.output == ""
+
+
 def test_cfgrib_cli_dump() -> None:
     runner = click.testing.CliRunner()