Addresses Copilot's round-17 review on #2035. A real crash, and a class the
earlier prototype work missed rather than a narrower version of it.
`toString`, `constructor` and `__proto__` are valid RFC 6570 variable names,
and `completions` starts as `{}`. So for such a name:
completions["toString"] ?? [] => the prototype's FUNCTION
`??` catches only null and undefined, so that function went to Mantine's
Autocomplete as its `data`, and the field crashed on first render with
`TypeError: data.map is not a function` -- reproduced by reverting the fix
under the new test.
The earlier rounds fixed this for the *values* map, which is seeded with
every declared variable and so always has the key as an own property. The
completions map is the one name-keyed map this component reads WITHOUT
having seeded it, which is what made it the surviving instance. Both reads
now go through `Object.hasOwn` -- the render, and the stale-dropdown check
that clears a variable's options on the next keystroke.
Only the autocomplete branch could reach it, so the regression drives that
branch: completions supported, a `{toString}` template, type and submit.
npm run ci passes.
Signed-off-by: cliffhall <cliff@futurescale.com>
05bbfe5074