Add warnings for .get() parsing changes in 0.15.0

arrow/factory.py

@@ -9,6 +9,7 @@
 from __future__ import absolute_import
 
 import calendar
+import warnings
 from datetime import date, datetime, tzinfo
 from time import struct_time
 
@@ -19,6 +20,21 @@
 from arrow.util import is_timestamp, isstr
 
 
+class ArrowParseWarning(DeprecationWarning):
+    """Raised when arrow.get() is passed a string with no formats and matches incorrectly
+    on one of the default formats.
+
+    e.g.
+    arrow.get('blabla2016') -> <Arrow [2016-01-01T00:00:00+00:00]>
+    arrow.get('13/4/2045') -> <Arrow [2045-01-01T00:00:00+00:00]>
+
+    In version 0.15.0 this warning will become a ParserError.
+    """
+
+
+warnings.simplefilter("always", ArrowParseWarning)
+
+
 class ArrowFactory(object):
     """ A factory for generating :class:`Arrow <arrow.arrow.Arrow>` objects.
 
@@ -172,6 +188,11 @@ def get(self, *args, **kwargs):
 
             # (str) -> parse.
             elif isstr(arg):
+                warnings.warn(
+                    "The .get() parsing method without a format string will parse more strictly in version 0.15.0."
+                    "See https://github.com/crsmithdev/arrow/issues/612 for more details.",
+                    ArrowParseWarning,
+                )
                 dt = parser.DateTimeParser(locale).parse_iso(arg)
                 return self.type.fromdatetime(dt, tz)
 
@@ -214,6 +235,11 @@ def get(self, *args, **kwargs):
 
             # (str, format) -> parse.
             elif isstr(arg_1) and (isstr(arg_2) or isinstance(arg_2, list)):
+                warnings.warn(
+                    "The .get() parsing method with a format string will parse more strictly in version 0.15.0."
+                    "See https://github.com/crsmithdev/arrow/issues/612 for more details.",
+                    ArrowParseWarning,
+                )
                 dt = parser.DateTimeParser(locale).parse(args[0], args[1])
                 return self.type.fromdatetime(dt, tzinfo=tz)