251606460 dropped each component's window hooks on unmount, but deleted them
unconditionally, and that is wrong as soon as two of the same component share a
page -- which research-map-plus-grid and the Big Picture composite both arrange.
B mounts and overwrites A's hooks; A unmounts and deletes them; B is still on
screen with its verify hooks gone. Not a leak, and not visible to a reader: the
cost lands on rega, as a hook reported missing on a map that is perfectly
healthy, which is a more expensive thing to chase than this is to write.
people-groups-grid already compared identity before releasing. research-map (4
hooks) and the dashboard map panel (3) did not, so the commit was uneven with
itself; gospel's d3597f3d1 settled on the same identity-checked pattern, and one
pattern across the fleet is what lets the check enforce it later.
Each hook is now held in a local as it is installed -- window.__x = _hookX = (…)
-- declared outside the block that assigns it, because a const in there is
invisible to onBeforeUnmount. The release compares before deleting, one key per
line, so the check can read both halves.
The check reports how many releases are identity-checked and enforces it under
STRICT_IDENTITY=1, which is off only because other owners have not adopted the
pattern yet. Flipping it later is a smaller change than re-deriving this.
Two things it taught me while I wrote it. Enforcement first flagged the grid,
which WAS identity-checked -- the comparison simply sat on the line above the
delete, and looking only at the delete's own line dictated formatting instead of
recognising correct code; the window now covers the lines leading up to it. And
the pattern is tested for BEHAVIOUR, not presence: two hooks installed in turn,
the first unmount must leave the second working, the second must leave nothing.
3ea48ebb42