feat: add timedelta support (#134)

As requested in #133, I have added support for parsing and converting an
ISO 8601 duration to a `timedelta`. Additionally, I have added automated
tests to verify the behavior and a usage example in the `README.md`.
Please feel free to let me know if I failed to add tests somewhere that
should really include some tests.

README.md

@@ -40,6 +40,7 @@ str_name = ${?HOME}
 dash-to-underscore = true
 float_num = 2.2
 iso_datetime = "2000-01-01T20:00:00"
+iso_duration = "P123DT4H5M6S"
 # this is a comment
 list_data = [
     a
@@ -87,6 +88,7 @@ class Config:
     dash_to_underscore: bool
     float_num: float
     iso_datetime: datetime
+    iso_duration: timedelta
     list_data: List[Text]
     nested: Nested
     nested_list: List[Nested]

confs/readme.hocon

@@ -3,6 +3,7 @@ str_name = ${?HOME}
 dash-to-underscore = true
 float_num = 2.2
 iso_datetime = "2000-01-01T20:00:00"
+iso_duration = "P123DT4H5M6S"
 # this is a comment
 list_data = [
     a

dataconf/utils.py

@@ -3,6 +3,7 @@
 from dataclasses import fields
 from dataclasses import is_dataclass
 from datetime import datetime
+from datetime import timedelta
 from enum import Enum
 from enum import IntEnum
 from inspect import isclass
@@ -28,6 +29,8 @@
 from pyhocon import ConfigFactory
 from pyhocon.config_tree import ConfigList
 from pyhocon.config_tree import ConfigTree
+from isodate import parse_duration
+from isodate import Duration
 import pyparsing
 
 from dataconf.version import PY310up
@@ -220,6 +223,20 @@ def __parse(value: any, clazz: Type, path: str, strict: bool, ignore_unexpected:
                 f"expected type {clazz} at {path}, cannot parse due to {e}"
             )
 
+    if clazz is timedelta:
+        dt = __parse_type(value, clazz, path, isinstance(value, str))
+        try:
+            duration = parse_duration(dt)
+            if isinstance(duration, Duration):
+                raise ParseException(
+                    "The ISO 8601 duration provided can not contain years or months"
+                )
+            return duration
+        except ValueError as e:
+            raise ParseException(
+                f"expected type {clazz} at {path}, cannot parse due to {e}"
+            )
+
     if clazz is relativedelta:
         return __parse_type(value, clazz, path, isinstance(value, relativedelta))
 

pyproject.toml

@@ -37,6 +37,7 @@ pyhocon = "0.3.59"
 python-dateutil = "^2.8.2"
 PyYAML = "^6.0.1"
 pyparsing = "2.4.7"
+isodate = "^0.6.1"
 
 [tool.poetry.group.dev.dependencies]
 pytest = ">=7.4.2,<9.0.0"

tests/test_parse.py

@@ -1,6 +1,7 @@
 from dataclasses import dataclass
 from dataclasses import field
 from datetime import datetime
+from datetime import timedelta
 from datetime import timezone
 from enum import Enum
 from enum import IntEnum
@@ -303,6 +304,49 @@ class A:
         with pytest.raises(ParseException):
             assert loads(conf, A)
 
+    def test_duration(self) -> None:
+        @dataclass
+        class A:
+            b: timedelta
+
+        conf = """
+        b = "P123DT4H5M6S"
+        """
+        assert loads(conf, A) == A(b=timedelta(days=123, hours=4, minutes=5, seconds=6))
+
+    def test_bad_duration(self) -> None:
+        @dataclass
+        class A:
+            b: timedelta
+
+        conf = """
+        b = "P123D4H5M6S"
+        """
+        with pytest.raises(ParseException):
+            assert loads(conf, A)
+
+    def test_unsupported_duration_with_year(self) -> None:
+        @dataclass
+        class A:
+            b: timedelta
+
+        conf = """
+        b = "P1Y"
+        """
+        with pytest.raises(ParseException):
+            assert loads(conf, A)
+
+    def test_unsupported_duration_with_month(self) -> None:
+        @dataclass
+        class A:
+            b: timedelta
+
+        conf = """
+        b = "P1M"
+        """
+        with pytest.raises(ParseException):
+            assert loads(conf, A)
+
     def test_optional_with_default(self) -> None:
         @dataclass
         class A:

tests/test_regression.py

@@ -2,6 +2,7 @@
 from dataclasses import dataclass
 from dataclasses import field
 from datetime import datetime
+from datetime import timedelta
 import os
 import tempfile
 from typing import Dict
@@ -45,6 +46,7 @@ class Config:
             dash_to_underscore: bool
             float_num: float
             iso_datetime: datetime
+            iso_duration: timedelta
             list_data: List[Text]
             nested: Nested
             nested_list: List[Nested]
@@ -63,6 +65,7 @@ class Config:
             dash_to_underscore=True,
             float_num=2.2,
             iso_datetime=datetime(2000, 1, 1, 20),
+            iso_duration=timedelta(days=123, hours=4, minutes=5, seconds=6),
             list_data=["a", "b"],
             nested=Nested(a="test", b=1),
             nested_list=[Nested(a="test1", b=2.5)],