Aglet

Verify Duplicate Headers Stay Distinct During Import

Verification should prove that repeated labels never silently merge source columns. Use distinct fixture values and compare the saved destination fields with an independent mapping. A preview that shows both columns is only partial evidence; the selected identities must remain distinct when the confirmed import executes.

Check whether the outcome improved

  1. Exercise repeated and normalized labels

    Check identical headings, labels differing only by surrounding spaces, and labels that normalize to the same case where normalization exists. Include unique-header controls. Confirm the documented behavior: distinct selectable columns or a clear unsupported-layout failure, rather than an arbitrary choice of whichever column happens to be read last.

  2. Carry separate mappings through confirmation

    Map the repeated columns to different supported destinations and inspect their sample values. Continue with the same file and confirm each selection remains attached to its source column. Reopen the mapping step if supported to catch a state reconstruction that mistakenly resolves both selections by visible label.

  3. Compare final values and reordered input

    Inspect exact destination values after the controlled import. Repeat with a reordered source and an explicitly confirmed mapping for that layout. The result should follow the reviewed source identity, not an old position or generated label carried over from a previous file with the same repeated headings.

What to carry forward

Accept when supported duplicate layouts remain unambiguous from preview through saved assignment and unsupported ones fail clearly before commitment. Record normalized-label and reordered-file coverage. Keep verification open if only visual labels were checked; different labels on screen do not by themselves prove distinct execution identities.

Technical background: DuckDB documentation.

Keep the decision with the work.

Use a Work Item in Aglet to record the problem, the evidence you have, and the next decision. Add an owner and priority, then keep updates in the discussion so the next person can follow the reasoning.

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