fix: %j (day of year) format directive overwrote parsed month/day

[gaoflow]

Bug

When a format string passed to parse_with_formats (via dateparser.parse(..., date_formats=[...]) or DateDataParser.get_date_data(..., date_formats=[...])) contained %j (day of year), the correctly-parsed month and day were silently replaced with today's date:

import dateparser

# Day 100 of 2023 is April 10
dateparser.parse("2023-100", date_formats=["%Y-%j"])
# Before fix: datetime(2023, 6, 25)  ← today, wrong
# After fix:  datetime(2023, 4, 10)  ← correct

This also affects %-j (no-padding variant).

Root cause

parse_with_formats computed:

missing_month = not any(m in date_format for m in ["%m", "%b", "%B"])
missing_day = "%d" not in date_format

Neither check recognises %j. A successful strptime call with %j always populates both the month and day fields in the returned datetime object, so the parsed values should be kept as-is.

The existing _get_missing_parts helper in dateparser/utils/__init__.py already listed %j and %-j under the "day" directive, but not under "month". This was a secondary inconsistency: since %j encodes a day-of-year that uniquely determines the month, it implicitly provides month information.

Fix

1. Add %j and %-j to the "month" directive list in _get_missing_parts.
2. Replace the ad-hoc missing_month/missing_day expressions in parse_with_formats with a single _get_missing_parts call, which is the authoritative and already-tested source for this logic.

All 22 703 existing tests continue to pass. Three new regression tests are included.

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This pull request was prepared with the assistance of AI, under my direction and review.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.11%. Comparing base (33e913c) to head (d85c420).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1345   +/-   ##
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  Coverage   97.11%   97.11%           
=======================================
  Files         235      235           
  Lines        2909     2910    +1     
=======================================
+ Hits         2825     2826    +1     
  Misses         84       84           

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[Copilot]

Pull request overview

Fixes incorrect behavior in parse_with_formats where using the %j (day-of-year) directive could cause the parsed month/day to be overwritten by “today’s” month/day, by centralizing “missing parts” detection in the existing _get_missing_parts utility.

Changes:

• Treat %j / %-j as providing month information in _get_missing_parts (since day-of-year implies month/day).
• Replace ad-hoc “missing month/day” checks in parse_with_formats with _get_missing_parts.
• Add regression tests covering %j parsing for day-of-year inputs (including leap-year behavior).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
dateparser/date.py	Uses _get_missing_parts to correctly detect which parts are missing for custom strptime formats, avoiding incorrect overwrites when %j is present.
dateparser/utils/__init__.py	Updates directive mapping so %j / %-j count as providing month information.
tests/test_date.py	Adds regression coverage for %j day-of-year parsing behavior.

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[serhii73]

Thanks!