First half of the mass import: a file becomes named sheets with typed rows,
and every rule that could reject a row is stated in one place.
Nothing here touches a database. The parser turns bytes into sheets, the
schema says which columns exist, and validation reports findings — the
existing state is passed in as a parameter. That is what makes 36 tests
possible without a connection, and the rules are the part worth testing.
Three decisions where the easy choice would have been silent corruption:
- A two-digit year is refused. "15.08.68" is 1968 as a birth date and 2068
as a contract end, and any rule invented here creates people not yet
born.
- "31.02.2026" is refused. Date turns it into March 3rd without complaint.
- An unrecognised value in a yes/no column is an error, not "no". Read the
other way, a typo in "Betriebsrat" quietly removes someone's dismissal
protection.
CSV is parsed rather than split. German Excel writes semicolons because the
comma is the decimal separator, so the delimiter is sniffed from the header;
a semicolon inside a quoted address would otherwise shift every following
column and import the row plausibly wrong. Quoted newlines, doubled quotes
and the byte-order mark Excel prepends are all handled — the last one makes
the first column read as "?Personalnummer", which is invisible in an editor.
Validation collects every finding instead of stopping at the first. With 800
rows that is the difference between correcting once and uploading eight
hundred times.
One rule earns its place from experience: a history event dated before the
entry it belongs to is refused here, with a row number, because the database
refuses it too — mid-insert, without one.
My own slip, caught by the type checker: `a ?? b ? c : d` does not mean what
it looks like; ?? binds tighter than the conditional.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Maximilian Stubhan
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