Documentation
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Overview ¶
Package nullcell holds the cross-adapter integration tests for the TWO absent-looking states of a `categorical_*` column — a null cell and a cell whose value IS the empty string.
The states are distinct inside a `.pulse` cohort by construction: null rides the per-record bitmap and "" is an ordinary dictionary entry. Keeping them distinct through an export and a re-import is a per-adapter obligation, and unlike `set_*` it cannot be met with an in-band marker: every text a sentinel could use is a legal categorical value, so the distinction rides io.NullAwareWriter / io.NullAwareReader instead.
Four adapters carry it (ndjson, jsonarray, arrow, parquet) and three do not (csv, tsv, excel). The gap is DOCUMENTED rather than silent, and the assertions here pin both halves — including the direction of the collapse, which must always be toward NULL. See io.NullAwareReader for the matrix and the reasons.
The package is test-only: every .go file but this one ends in _test.go. It follows the precedent set by io/settristate.
Source Files