MNT: Be more robust about closing files we've opened

Inspired by some alerts from CodeQL, though most were false alarms.

src/metpy/io/metar.py

@@ -4,6 +4,7 @@
 """Parse METAR-formatted data."""
 # Import the necessary libraries
 from collections import namedtuple
+import contextlib
 from datetime import datetime
 import warnings
 
@@ -521,11 +522,9 @@ def merge(x, key='     '):
         if len(tmp):
             yield ' '.join(tmp)
 
-    # Open the file
-    myfile = open_as_needed(filename, 'rt')
-
-    # Clean up the file and take out the next line (\n)
-    value = myfile.read().rstrip()
+    # Open the file and clean up and take out the next line (\n)
+    with contextlib.closing(open_as_needed(filename, 'rt')) as myfile:
+        value = myfile.read().rstrip()
     list_values = value.split('\n')
     list_values = list(filter(None, list_values))
 

src/metpy/plots/cartopy_utils.py

@@ -27,7 +27,7 @@ def geometries(self):
             # Ensure that the associated files are in the cache
             fname = f'{self.name}_{self.scaler.scale}'
             for extension in ['.dbf', '.shx']:
-                get_test_data(fname + extension)
+                get_test_data(fname + extension, as_file_obj=False)
             path = get_test_data(fname + '.shp', as_file_obj=False)
             return iter(tuple(shapereader.Reader(path).geometries()))
 

src/metpy/testing.py

@@ -7,6 +7,7 @@
 * unit-aware test functions
 * code for testing matplotlib figures
 """
+import contextlib
 import functools
 
 import numpy as np
@@ -57,30 +58,28 @@ def get_upper_air_data(date, station):
                       '2002-11-11T00Z_BNA': 'nov11_sounding.txt',
                       '2010-12-09T12Z_BOI': 'dec9_sounding.txt'}
 
-    fname = sounding_files[sounding_key]
-    fobj = get_test_data(fname)
+    # Initiate lists for variables
+    arr_data = []
 
     def to_float(s):
         # Remove all whitespace and replace empty values with NaN
         if not s.strip():
             s = 'nan'
         return float(s)
 
-    # Skip dashes, column names, units, and more dashes
-    for _ in range(4):
-        fobj.readline()
-
-    # Initiate lists for variables
-    arr_data = []
+    with contextlib.closing(get_test_data(sounding_files[sounding_key])) as fobj:
+        # Skip dashes, column names, units, and more dashes
+        for _ in range(4):
+            fobj.readline()
 
-    # Read all lines of data and append to lists only if there is some data
-    for row in fobj:
-        level = to_float(row[0:7])
-        values = (to_float(row[7:14]), to_float(row[14:21]), to_float(row[21:28]),
-                  to_float(row[42:49]), to_float(row[49:56]))
+        # Read all lines of data and append to lists only if there is some data
+        for row in fobj:
+            level = to_float(row[0:7])
+            values = (to_float(row[7:14]), to_float(row[14:21]), to_float(row[21:28]),
+                      to_float(row[42:49]), to_float(row[49:56]))
 
-        if any(np.invert(np.isnan(values[1:]))):
-            arr_data.append((level,) + values)
+            if any(np.invert(np.isnan(values[1:]))):
+                arr_data.append((level,) + values)
 
     p, z, t, td, direc, spd = np.array(arr_data).T
 

tests/io/test_nexrad.py

@@ -2,7 +2,7 @@
 # Distributed under the terms of the BSD 3-Clause License.
 # SPDX-License-Identifier: BSD-3-Clause
 """Test the `nexrad` module."""
-
+import contextlib
 from datetime import datetime
 from io import BytesIO
 import logging
@@ -76,7 +76,8 @@ def read(self, n=None):
 
 def test_doubled_file():
     """Test for #489 where doubled-up files didn't parse at all."""
-    data = get_test_data('Level2_KFTG_20150430_1419.ar2v').read()
+    with contextlib.closing(get_test_data('Level2_KFTG_20150430_1419.ar2v')) as infile:
+        data = infile.read()
     fobj = BytesIO(data + data)
     f = Level2File(fobj)
     assert len(f.sweeps) == 12