Fixed ISO-format decoding problems

fhirdatetime/__init__.py

@@ -29,6 +29,7 @@
 >>> FhirDateTime(2021) > FhirDateTime(2021, 3, 15)
 False
 """
+import re
 from datetime import MAXYEAR, MINYEAR, date, datetime, timezone, tzinfo as tzinfo_
 from operator import itemgetter
 from typing import Optional, Union
@@ -43,10 +44,13 @@
 )
 
 __all__ = ["FhirDateTime", "__version__"]
-__version__ = "0.1.0b6"
+__version__ = "0.1.0b8"
 
 DATE_FIELDS = ("year", "month", "day")
 TIME_FIELDS = ("hour", "minute", "second", "microsecond")
+_y_pat = re.compile(r"^(\d{4})$")
+_ym_pat = re.compile(r"^(\d{4})-(\d{2})$")
+_ymd_pat = re.compile(r"^(\d{4})-(\d{2})-(\d{2})$")
 
 ComparableTypes = Union["FhirDateTime", datetime, date]
 
@@ -221,23 +225,29 @@ def isoformat(self, sep: str = "T", timespec: str = "auto") -> str:
     @classmethod
     def fromisoformat(cls, date_string: str):
         """Construct a FhirDateTime from the output of FhirDateTime.isoformat()."""
+        # Check for shorter formats first
+        for pat in (_y_pat, _ym_pat, _ymd_pat):
+            m = re.match(pat, date_string)
+            if m:
+                return FhirDateTime(*[int(p) for p in m.groups()])
+
         try:
             return super().fromisoformat(date_string)
         except (ValueError, IndexError):
             pass
 
-        for fmt in ("%Y-%m-%dT%H:%M:%S.%f%Z", "%Y", "%Y-%m", "%Y-%m-%d"):
+        for fmt in ("%Y-%m-%dT%H:%M:%S.%fZ", "%Y-%m-%dT%H:%M:%SZ"):
+            # These formats need to have the UTC timezone inserted after creation
+            try:
+                return cls.strptime(date_string, fmt).replace(tzinfo=timezone.utc)
+            except ValueError:
+                pass
+
+        for fmt in ("%Y-%m-%dT%H:%M:%S.%f%Z", "%Y-%m-%dT%H:%M:%S%Z"):
             try:
                 return cls.strptime(date_string, fmt)
             except ValueError as err:
                 last_err = err
-                continue
-        try:
-            return cls.strptime(date_string, "%Y-%m-%dT%H:%M:%S.%fZ").replace(
-                tzinfo=timezone.utc
-            )
-        except ValueError:
-            pass
         raise last_err
 
     @staticmethod

pyproject.toml

@@ -6,7 +6,7 @@ combine_as_imports = true
 
 [tool.poetry]
 name = "fhirdatetime"
-version = "0.1.0b6"
+version = "0.1.0b8"
 description = "A datetime-compatible class for FHIR date/datetime values."
 authors = ["Mike Mabey <mmabey@ieee.org>"]
 homepage = "https://github.com/mmabey/fhirdatetime"

tests/test_fhirdatetime.py

@@ -16,7 +16,7 @@
 
 def test_version():
     """Check library version is what it should be."""
-    ver = "0.1.0b6"
+    ver = "0.1.0b8"
     assert __version__ == ver
     with open("pyproject.toml") as proj:
         for line in proj:
@@ -249,3 +249,7 @@ def test_other_methods():
         2020, 5, 4, 13, 42, 54, 295815, timezone(timedelta(hours=3))
     )
     assert dt.timestamp() == 1588588974.295815
+
+    assert str(FhirDateTime("2020")) == "2020"
+    assert str(FhirDateTime("2020-05")) == "2020-05"
+    assert str(FhirDateTime("2020-05-04")) == "2020-05-04"