[shyamsharmas124-commits]

Summary

This PR addresses two interconnected edge cases in TimeSeries.strip(), TimeSeries.longest_contiguous_slice(), and extract_subseries():

1. extract_subseries() crashed on boundary NaNs with mode="any":

   • In darts/utils/missing_values.py, series.strip() was called with default how="all" instead of how=mode. When mode="any" on a multivariate series with partial NaNs at the start or end, those rows were left unstripped.
   • series.gaps(mode=mode) then detected boundary gaps starting at index 0 or ending at index -1, resulting in end_times = gap_start - freq (outside the series start) and crashing with ValueError: Timestamp must be between ... or ValueError: The index corresponding to the provided point (-1) should be a valid index in series.
   • Now passes how=mode to series.strip(how=mode) and returns [] immediately if len(series) == 0.

2. TimeSeries.strip() failed on all-NaN and empty series:

   • In _finite_rows_boundaries(), finite_rows.argmax() returns 0 on an all-False boolean array. For an all-NaN series (or under how="any" when all rows have at least one NaN), strip() returned the entire series of NaNs untouched instead of stripping them. On empty series, argmax() threw ValueError: attempt to get argmax of an empty sequence.
   • Now checks if not finite_rows.any(): return None, None and TimeSeries.strip() returns self[:0].

3. TimeSeries.longest_contiguous_slice() boundary NaNs:

   • Now calls self.strip(how=mode) and returns stripped_series immediately if len(stripped_series) == 0.

Changes Made

• darts/timeseries.py:
  • _finite_rows_boundaries(): Return None, None if not finite_rows.any().
  • TimeSeries.strip(): Return self[:0] if first_finite_row is None.
  • TimeSeries.longest_contiguous_slice(): Pass how=mode to self.strip(how=mode) and check for empty stripped series.
• darts/utils/missing_values.py:
  • extract_subseries(): Pass how=mode to series.strip(how=mode) and return [] if len(series) == 0.
• darts/tests/:
  • Added unit tests in test_timeseries_multivariate.py, test_timeseries.py, and test_utils.py covering all-NaN series, empty series, and multivariate partial-NaN boundaries.
• CHANGELOG.md:
  • Added entry under [Unreleased] -> **Fixed**.

Verification

All 250 unit tests across test_timeseries_multivariate.py, test_utils.py, test_missing_values.py, and test_longest_contiguous_slice pass cleanly with zero linting/formatting errors (ruff check and ruff format).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.13%. Comparing base (555c8d1) to head (e7f0a53).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3285   +/-   ##
=======================================
  Coverage   97.13%   97.13%           
=======================================
  Files         175      175           
  Lines       19408    19416    +8     
=======================================
+ Hits        18851    18859    +8     
  Misses        557      557           

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