fix(common): remove unsupported cross join mode from left_join_df

[rusackas]

Follow-up to #41334.

SUMMARY

left_join_df's how parameter is typed Literal["left", "right", "inner", "outer", "cross"], but the join is implemented via DataFrame.set_index(...).join(...), whose underlying Index.join doesn't support "cross" the way pd.merge does. Passing how="cross" silently drops the join keys instead of producing a real cross join, so the type signature was advertising a mode that doesn't actually work.

This removes "cross" from the Literal in left_join_df (superset/common/utils/dataframe_utils.py). ExploreMixin._perform_join in superset/models/helpers.py forwards its own how parameter straight into left_join_df, so its signature is narrowed the same way to keep mypy happy and stay consistent.

Neither function is ever called with how="cross" today (join_offset_dfs, the only caller, only ever passes "left" or "outer" for the time-comparison full-range option added in #41334), so this is a type-only fix with no behavior change.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A - type-only change, no UI impact.

TESTING INSTRUCTIONS

• pytest tests/unit_tests/common/test_time_shifts.py and pytest tests/unit_tests/common/test_query_context_processor.py -k join still pass.
• pre-commit run (including mypy) passes on the changed files, confirming the narrower type doesn't break the one call site.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration
• Introduces new feature or API
• Removes existing feature or API

[bito-code-review]

Code Review Agent Run #f53926

Actionable Suggestions - 0

Review Details

• Files reviewed - 2 · Commit Range: eb321ba..eb321ba

  • superset/common/utils/dataframe_utils.py
  • superset/models/helpers.py
• Files skipped - 0
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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.59%. Comparing base (0dedc55) to head (eb321ba).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #43016   +/-   ##
=======================================
  Coverage   66.59%   66.59%           
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  Files        2863     2863           
  Lines      161681   161681           
  Branches    37249    37249           
=======================================
  Hits       107678   107678           
  Misses      51961    51961           
  Partials     2042     2042           

Flag	Coverage Δ
hive	38.21% <ø> (ø)
mysql	57.76% <ø> (ø)
postgres	57.81% <ø> (ø)
presto	40.18% <ø> (ø)
python	59.20% <ø> (ø)
sqlite	57.43% <ø> (ø)
unit	100.00% <ø> (ø)

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[Copilot]

Pull request overview

This PR tightens type annotations around Superset’s DataFrame join helpers to match actual pandas join capabilities, removing an advertised "cross" join mode that isn’t supported by the underlying DataFrame.set_index(...).join(...) implementation.

Changes:

• Narrow left_join_df(..., how=...) to exclude "cross" from its Literal[...] type.
• Narrow ExploreMixin._perform_join(..., how=...) to the same set of supported join modes to keep typing consistent.
• Add an inline comment documenting why "cross" is intentionally unsupported here.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
superset/common/utils/dataframe_utils.py	Removes "cross" from left_join_df’s how type and documents the limitation of the join implementation.
superset/models/helpers.py	Narrows _perform_join’s how type to match left_join_df and avoid propagating an unsupported mode.

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[sha174n]

LGTM. cross was never valid for the Index.join path anyway, so narrowing the Literal is correct and cannot affect valid callers. CI green.