Three CSV edge cases

Original synthetic examples by Shruti. Run node run-lab.mjs with Node 22+ to check all three supplied expectations.

Ambiguous keys

Left CSV

id,value
C-01,ready
C-01,draft

Right CSV

id,value
C-01,ready

Reveal expected result and explanation

Expected counts: {"unchanged": 0, "changed": 0, "only_left": 0, "only_right": 0, "ambiguous": 1, "blank_key": 0, "invalid_numeric": 0}

Two source records share an ID. No row is selected silently and no business resolution is inferred.

Left CSV

id,value
C-01,"first
second"

Right CSV

id,value

C-01,"first
second"

Reveal expected result and explanation

Expected counts: {"unchanged": 1, "changed": 0, "only_left": 0, "only_right": 0, "ambiguous": 0, "blank_key": 0, "invalid_numeric": 0}

A quoted newline belongs to one field. Physical line counts do not equal CSV record counts.

Left CSV

id,value
C-01,"unfinished

Right CSV

id,value
C-01,ready

Reveal expected result and explanation

Expected rejection: unclosed quoted

Repair the input using the system of record. Guessing where a quoted field ends could silently change records.