I hand-listed the names a column could shadow: count and index, the two
tuple methods. Then I wrote keys(), _asdict() and _fields on the same
class and did not go back. A column called "keys" returned a bound
method instead of a value, silently, which is precisely the failure
shape this driver spent a fortnight removing from its decoders.
The fix is not a longer list. The reserved set is now computed from
dir(Row), so adding a method later cannot reopen the hole, and the test
is parametrized over that computed set so it grows with the class.
_fields and _map moved to name-mangled attributes. They are read by
repr() and _asdict(), so shadowing the public _fields with a column
would have made the machinery report the column value instead of the
column names. Mangling keeps the two apart, and there is a test that
shadows _fields and checks repr still works.
Also exercised, and all clean: value-identical output against the plain
tuple path across twenty columns covering every awkward type plus a
fully NULL row, which is the strongest available statement that Row is a
presentation layer and not a bug; zero-column and 500-column rows;
unicode, spaced, digit-leading, empty-string and dunder column names;
rows outliving eviction of their class from the bounded cache; the four
async fetch routes and the async pool; and twelve threads racing on the
class cache, which correctly share one class per shape.
472 tests on 15 and 14.10, 471 on 12.10.
Ryan Malloy
ce5a582048