id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
36747	parse_duration() fails to parse valid ISO-8601 durations including years, months, and weeks due to incorrect regex	florianvazelle		"== **Description**

`django.utils.dateparse.parse_duration()` claims to support ISO-8601 duration strings, but the current implementation only handles the `PnDTnHnMnS` subset. Valid ISO-8601 components such as years (`Y`), months (`M`), and weeks (`W`) are not supported.

The internal regex used for ISO-8601 durations:

{{{
iso8601_duration_re = _lazy_re_compile(
    r""^(?P<sign>[-+]?)""
    r""P""
    r""(?:(?P<days>\d+([.,]\d+)?)D)?""
    r""(?:T""
    r""(?:(?P<hours>\d+([.,]\d+)?)H)?""
    r""(?:(?P<minutes>\d+([.,]\d+)?)M)?""
    r""(?:(?P<seconds>\d+([.,]\d+)?)S)?""
    r"")?""
    r""$""
)
}}}

This means Django currently rejects valid duration strings such as:


{{{
P1Y2M
P3W
P1Y
P2M10DT2H
}}}



Despite the documentation suggesting ISO-8601 support, these forms cannot be parsed.

== **Steps to Reproduce**

{{{
from django.utils.dateparse import parse_duration

parse_duration(""P1Y"")      # returns None
parse_duration(""P2M"")      # returns None
parse_duration(""P3W"")      # returns None
parse_duration(""P1Y2M3DT4H"")  # returns None
}}}

== **Expected Behavior**

`parse_duration()` should parse all valid ISO-8601 durations that can be represented as `timedelta`, including:

* `PnW`
* `PnYnMnD`
* ...

Django should capture each calendar unit, or clearly state limitations.

== **Proposed Fix**

1. Replace the current `iso8601_duration_re` with one that uses distinct group names for each ISO-8601 calendar unit:



{{{
iso8601_duration_re = _lazy_re_compile(
    r""^(?P<sign>[-+]?)""
    r""P""
    r""(?:(?P<years>\d+([.,]\d+)?)Y)?""
    r""(?:(?P<months>\d+([.,]\d+)?)M)?""
    r""(?:(?P<weeks>\d+([.,]\d+)?)W)?""
    r""(?:(?P<days>\d+([.,]\d+)?)D)?""
    r""(?:T""
    r""(?:(?P<hours>\d+([.,]\d+)?)H)?""
    r""(?:(?P<minutes>\d+([.,]\d+)?)M)?""
    r""(?:(?P<seconds>\d+([.,]\d+)?)S)?""
    r"")?""
    r""$""
)
}}}



2. Extend `parse_duration()` to convert these new fields to timedelta.


{{{
def parse_duration(value):
    match = (
        standard_duration_re.match(value)
        or iso8601_duration_re.match(value)
        or postgres_interval_re.match(value)
    )
    if match:
        kw = match.groupdict()
        sign = -1 if kw.pop(""sign"", ""+"") == ""-"" else 1
        if kw.get(""microseconds""):
            kw[""microseconds""] = kw[""microseconds""].ljust(6, ""0"")
        kw = {k: float(v.replace("","", ""."")) for k, v in kw.items() if v is not None}
        days = datetime.timedelta(kw.pop(""days"", 0.0) or 0.0)

        if match.re == iso8601_duration_re:
+           years = kw.pop(""years"", 0.0)
+           months = kw.pop(""months"", 0.0)
+           weeks = kw.pop(""weeks"", 0.0)
+            
+           days = datetime.timedelta(years=years, months=months, days=kw.pop(""days"", 0.0) + (weeks * 7))
            days *= sign

        return days + sign * datetime.timedelta(**kw)
}}}


I can provide a full patch (tests + implementation) if desired.
"	Bug	new	Uncategorized	5.2	Normal				Unreviewed	0	0	0	0	0	0