config: More flexible date parsing.

* Accept partial dates, filling in the current year and month as needed.
* Accept more separators.

oxrlib/config.py

@@ -17,14 +17,11 @@ def currency_code(s):
 def currency_list(s):
     return [currency_code(code.strip()) for code in s.split(',')]
 
-def date_from(fmt_s):
-    def date_from_fmt(s):
-        return datetime.datetime.strptime(s, fmt_s).date()
-    return date_from_fmt
-
 class Configuration:
+    DATE_SEPS = frozenset('.-/ ')
     DEFAULT_CONFIG_PATH = pathlib.Path(HOME_PATH, '.config', 'oxrlib.ini')
     PREPOSITIONS = frozenset(['in', 'to', 'into'])
+    TODAY = datetime.date.today()
 
     def __init__(self, arglist):
         argparser = self._build_argparser()
@@ -50,6 +47,30 @@ class Configuration:
         else:
             post_hook()
 
+    def _date_from_s(self, s):
+        number_digits = [[]]
+        seen_seps = set()
+        bad_c = False
+        for c in s.strip():
+            if c.isdigit():
+                number_digits[-1].append(c)
+            elif c in self.DATE_SEPS:
+                seen_seps.add(c)
+                number_digits.append([])
+            else:
+                bad_c = True
+        numbers = [int(''.join(digit_list), 10) for digit_list in number_digits]
+        if bad_c or (len(numbers) > 3) or (len(seen_seps) > 1):
+            raise ValueError("can't parse date from {!r}".format(s))
+        replacements = {}
+        try:
+            replacements['day'] = numbers[-1]
+            replacements['month'] = numbers[-2]
+            replacements['year'] = numbers[-3]
+        except IndexError:
+            pass
+        return self.TODAY.replace(**replacements)
+
     def _build_argparser(self):
         prog_parser = argparse.ArgumentParser()
         prog_parser.add_argument(
@@ -61,7 +82,7 @@ class Configuration:
 
         hist_parser = subparsers.add_parser(
             'historical', aliases=['hist'],
-            usage='%(prog)s YYYY-MM-DD [[amount] code] [[in] code]',
+            usage='%(prog)s [[YYYY-]MM-]DD [[amount] code] [[in] code]',
             help="Show a currency conversion or rate from a past date",
         )
         hist_parser.set_defaults(
@@ -94,8 +115,9 @@ class Configuration:
         )
         hist_parser.add_argument(
             'date',
-            type=date_from('%Y-%m-%d'),
-            help="Use rates from this date, in YYYY-MM-DD format"
+            type=self._date_from_s,
+            help="Use rates from this date, in YYYY-MM-DD format. "
+            "If you omit the year or month, it fills in the current year/month."
         )
         hist_parser.add_argument(
             'word1', nargs='?', metavar='first code',
@@ -144,6 +166,10 @@ class Configuration:
             self.error(': '.join(errmsg))
 
     def _post_hook_historical(self):
+        year = self.args.date.year
+        if year < 100:
+            # Don't let the user specify ambiguous dates.
+            self.error("historical data not available from year {}".format(year))
         self._read_from_conffile('base', 'Historical', 'USD', currency_code)
         self._read_from_conffile('signed_currencies', 'Historical', self.args.base, currency_list)
         self._read_from_conffile('ledger', 'Historical', False, getter='getboolean')

setup.py

@@ -5,7 +5,7 @@ from setuptools import setup
 setup(
     name='oxrlib',
     description="Library to query the Open Exchange Rates (OXR) API",
-    version='1.2',
+    version='1.3',
     author='Brett Smith',
     author_email='brettcsmith@brettcsmith.org',
     license='GNU AGPLv3+',

tests/test_Configuration.py

@@ -1,3 +1,4 @@
+import datetime
 import decimal
 import os
 
@@ -78,3 +79,39 @@ def test_historical_argparsing_failure(arglist, any_date):
         pass
     else:
         assert not vars(config.args), "bad arglist succeeded"
+
+@pytest.mark.parametrize('date_s,expect_year,expect_month,expect_day', [
+    ('5', 1965, 4, 5),
+    ('05', 1965, 4, 5),
+    ('3-6', 1965, 3, 6),
+    ('5.10', 1965, 5, 10),
+    ('06-09', 1965, 6, 9),
+    ('917/12/12', 917, 12, 12),
+    ('2017-11-1', 2017, 11, 1),
+])
+def test_good_date_parsing(date_s, expect_year, expect_month, expect_day):
+    oxrlib.config.Configuration.TODAY = datetime.date(1965, 4, 3)
+    config = config_from(os.devnull, ['historical', date_s])
+    actual_date = config.args.date
+    assert actual_date.year == expect_year
+    assert actual_date.month == expect_month
+    assert actual_date.day == expect_day
+
+@pytest.mark.parametrize('date_s', [
+    '99',
+    '8-88',
+    '77-7',
+    '0xf-1-2',
+    '0b1-3-4',
+    '2017/5.9',
+    '2018-6/10',
+    '1-2-3-4',
+    '12/11/10',
+])
+def test_bad_date_parsing(date_s):
+    try:
+        config = config_from(os.devnull, ['historical', date_s])
+    except SystemExit:
+        pass
+    else:
+        assert not config.args.date, "date parsed from {!r}".format(date_s)