fix(types): handle connector >=4.3.0 interval year-month display format

[sfc-gh-kgadomski]

Summary

Fixes incorrect display of YEAR TO MONTH interval values when using snowflake-connector-python>=4.3.0.

Root Cause

snowflake-connector-python v4.3.0 changed the string representation of INTERVAL YEAR and INTERVAL MONTH types (see connector changelog: "Fix string representation of INTERVAL YEAR and INTERVAL MONTH types").

Previously, the connector always returned compound year-month format (e.g., +4-0 for 4 years, 0 months). Starting with v4.3.0, when the months component is zero, the connector returns just +4 (omitting the -0 suffix).

format_year_month_interval_for_display in type_utils.py only interpreted a simple +N value as years when the type was exactly INTERVAL YEAR (start_field=YEAR, end_field=YEAR). For INTERVAL YEAR TO MONTH (start_field=YEAR, end_field=MONTH), the simple +N value was incorrectly treated as months, producing:

INTERVAL '0-4' YEAR TO MONTH   (wrong: 0 years, 4 months)

instead of:

INTERVAL '4-0' YEAR TO MONTH   (correct: 4 years, 0 months)

Fix

When start_field is YEAR, always interpret a simple +N value (no dash) as years, regardless of end_field. This is correct for:

• Old connector (<4.3.0): always uses compound format +Y-M, so the simple-value branch is never reached for YEAR TO MONTH types — no behavioral change.
• New connector (>=4.3.0): uses +N when months=0 — now correctly interpreted as years.

Reproduction

from snowflake.snowpark._internal.type_utils import format_year_month_interval_for_display
from snowflake.snowpark.types import YearMonthIntervalType

# Bug: '+4' with YEAR TO MONTH type treated as 4 months instead of 4 years
result = format_year_month_interval_for_display('+4', YearMonthIntervalType.YEAR, YearMonthIntervalType.MONTH)
# Before: "INTERVAL '0-4' YEAR TO MONTH" (wrong)
# After:  "INTERVAL '4-0' YEAR TO MONTH" (correct)

This was discovered via Snowpark Connect (SCOS) CI where try_multiply(4, INTERVAL '1' YEAR) produced incorrect output after widening the connector version cap to <5.0.0.

Test plan

• Added parametrized unit tests covering both old compound format and new simple format for all interval subtypes (YEAR, MONTH, YEAR TO MONTH)
• All existing tests/unit/test_datatype_mapper.py tests pass

Made with Cursor

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.04%. Comparing base (d4e00e4) to head (bfcac42).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4215   +/-   ##
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  Coverage   95.04%   95.04%           
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  Files         171      171           
  Lines       43877    43877           
  Branches     7525     7525           
=======================================
+ Hits        41703    41704    +1     
  Misses       1368     1368           
+ Partials      806      805    -1     

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[sfc-gh-mayliu]

LGTM. Can you update changelog.md for this bugfix? Please merge main to get the test infra fix for a required check

[sfc-gh-yuwang]

nint: can we make the test follow the existing style in this suite?

[sfc-gh-yuwang]

Approved with a nint, please take a look before merge, thanks!