Allow format duration as ISO-8601

Author: sevdog

docs/api-guide/fields.md

@@ -396,7 +396,7 @@ The `validated_data` for these fields will contain a `datetime.timedelta` instan
 - `min_value` Validate that the duration provided is no less than this value.
 
 #### `DurationField` format strings
-Format strings may either be the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style intervals should be used (eg `'P4DT1H15M20S'`), or the special string `'standard'`, which indicates that Django interval format `'[DD] [HH:[MM:]]ss[.uuuuuu]'` hould be used (eg: `'4 1:15:20'`).
+Format strings may either be the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style intervals should be used (eg `'P4DT1H15M20S'`), or the special string `'standard'`, which indicates that Django interval format `'[DD] [HH:[MM:]]ss[.uuuuuu]'` should be used (eg: `'4 1:15:20'`).
 
 ---
 

rest_framework/__init__.py

@@ -23,6 +23,7 @@
 
 # Default datetime input and output formats
 ISO_8601 = 'iso-8601'
+STD_DURATION = 'standard'
 
 
 if django.VERSION < (3, 2):

rest_framework/fields.py

@@ -23,7 +23,7 @@
 from django.utils.dateparse import (
     parse_date, parse_datetime, parse_duration, parse_time
 )
-from django.utils.duration import duration_string
+from django.utils.duration import duration_iso_string, duration_string
 from django.utils.encoding import is_protected_type, smart_str
 from django.utils.formats import localize_input, sanitize_separators
 from django.utils.ipv6 import clean_ipv6_address
@@ -1380,9 +1380,11 @@ class DurationField(Field):
         'min_value': _('Ensure this value is greater than or equal to {min_value}.'),
     }
 
-    def __init__(self, **kwargs):
+    def __init__(self, format=empty, **kwargs):
         self.max_value = kwargs.pop('max_value', None)
         self.min_value = kwargs.pop('min_value', None)
+        if format is not empty:
+            self.format = format
         super().__init__(**kwargs)
         if self.max_value is not None:
             message = lazy_format(self.error_messages['max_value'], max_value=self.max_value)
@@ -1402,6 +1404,13 @@ def to_internal_value(self, value):
         self.fail('invalid', format='[DD] [HH:[MM:]]ss[.uuuuuu]')
 
     def to_representation(self, value):
+        output_format = getattr(self, 'format', api_settings.DURATION_FORMAT)
+
+        if output_format is None or isinstance(value, str):
+            return value
+
+        if output_format.lower() == ISO_8601:
+            return duration_iso_string(value)
         return duration_string(value)
 
 

rest_framework/settings.py

@@ -22,7 +22,7 @@
 from django.test.signals import setting_changed
 from django.utils.module_loading import import_string
 
-from rest_framework import ISO_8601
+from rest_framework import ISO_8601, STD_DURATION
 
 DEFAULTS = {
     # Base API policies
@@ -107,6 +107,8 @@
     'TIME_FORMAT': ISO_8601,
     'TIME_INPUT_FORMATS': [ISO_8601],
 
+    'DURATION_FORMAT': STD_DURATION,
+
     # Encoding
     'UNICODE_JSON': True,
     'COMPACT_JSON': True,

tests/test_fields.py

@@ -1633,6 +1633,29 @@ class TestDurationField(FieldValues):
     field = serializers.DurationField()
 
 
+class TestNoOutputFormatDurationField(FieldValues):
+    """
+    Values for `TimeField` with a no output format.
+    """
+    valid_inputs = {}
+    invalid_inputs = {}
+    outputs = {
+        datetime.timedelta(1): datetime.timedelta(1)
+    }
+    field = serializers.DurationField(format=None)
+
+
+class TestISOOutputFormatDurationField(FieldValues):
+    """
+    Values for `TimeField` with a custom output format.
+    """
+    valid_inputs = {}
+    invalid_inputs = {}
+    outputs = {
+        datetime.timedelta(days=3, hours=8, minutes=32, seconds=1, microseconds=123) : 'P3DT8H32M1S123MS'
+    }
+    field = serializers.TimeField(format='is0-8601')
+
 # Choice types...
 
 class TestChoiceField(FieldValues):