fix covid_hosp bool parsing

- `bool('false')` is `True`
- add a helper function to parse bool from str, allowing missing and 
empty values

note that prod database needs to be backfilled since previous 
acquisitions incorrectly casted 'false' and 'true' both to `True`

Author: dfarrow0

src/acquisition/covid_hosp/common/utils.py

@@ -37,6 +37,36 @@ def int_from_date(date):
 
     return int(date.replace('-', ''))
 
+  def parse_bool(value):
+    """Convert a string to a boolean.
+
+    Parameters
+    ----------
+    value : str
+      Boolean-like value, like "true" or "false".
+
+    Returns
+    -------
+    bool
+      If the string contains some version of "true" or "false".
+    None
+      If the string is None or empty.
+
+    Raises
+    ------
+    CovidHospException
+      If the string constains something other than a version of "true" or
+      "false".
+    """
+
+    if not value:
+      return None
+    if value.lower() == 'true':
+      return True
+    if value.lower() == 'false':
+      return False
+    raise CovidHospException(f'cannot convert "{value}" to bool')
+
   def get_entry(obj, *path):
     """Get a deeply nested field from an arbitrary object.
 

src/acquisition/covid_hosp/facility/database.py

@@ -23,7 +23,7 @@ class Database(BaseDatabase):
     ('zip', str),
     ('hospital_subtype', str),
     ('fips_code', str),
-    ('is_metro_micro', bool),
+    ('is_metro_micro', Utils.parse_bool),
     ('total_beds_7_day_avg', float),
     ('all_adult_hospital_beds_7_day_avg', float),
     ('all_adult_hospital_inpatient_beds_7_day_avg', float),

tests/acquisition/covid_hosp/common/test_utils.py

@@ -43,6 +43,29 @@ def test_int_from_date(self):
 
     self.assertEqual(Utils.int_from_date('2020-11-17'), 20201117)
 
+  def test_parse_bool(self):
+    """Parse a boolean value from a string."""
+
+    with self.subTest(name='None'):
+      self.assertIsNone(Utils.parse_bool(None))
+
+    with self.subTest(name='empty'):
+      self.assertIsNone(Utils.parse_bool(''))
+
+    with self.subTest(name='true'):
+      self.assertTrue(Utils.parse_bool('true'))
+      self.assertTrue(Utils.parse_bool('True'))
+      self.assertTrue(Utils.parse_bool('tRuE'))
+
+    with self.subTest(name='false'):
+      self.assertFalse(Utils.parse_bool('false'))
+      self.assertFalse(Utils.parse_bool('False'))
+      self.assertFalse(Utils.parse_bool('fAlSe'))
+
+    with self.subTest(name='exception'):
+      with self.assertRaises(CovidHospException):
+        Utils.parse_bool('maybe')
+
   def test_get_entry_success(self):
     """Get a deeply nested field from an arbitrary object."""