internal/lib/facet-walk.mjs's __srcFeatures (injected into the page by
check:facet-changes-map) and library/maps/pin-selection.js's readSourceFeatures (the
packet and zoomToLegendRow) answer the same question about the same private GeoJSON
field. They are two copies because one must be a string evaluated in a browser and the
other an ES module, so they cannot be one function -- but nothing tested that they
still agreed, and they had already stopped.
THE CROSS-CHECK FOUND A DIVERGENCE ON ITS FIRST RUN, which is the argument for it. A
source may hold a single Feature rather than a FeatureCollection; both engines accept
that. The product's reader handled it and the gate's did not, so the gate answered
"cannot measure" about a payload it could read perfectly well. Nobody reading either
file would have noticed: each is correct on its own terms. __srcFeatures now handles
it and the two agree.
ONE DIFFERENCE IS DELIBERATE AND IS NOW PINNED AS SUCH RATHER THAN WAIVED: on a
url-backed source the gate returns null while the product returns [] and warns. Both
are right for their caller -- a gate whose job is to tell "the map drew nothing" from
"I could not look" needs a third answer, while a selection returning null would break
the Set arithmetic every caller does on it. Asserted in both directions, so neither
side can quietly adopt the other's and call it a fix.
AND NEITHER MAY BE SILENT ABOUT A SHAPE IT DOES NOT KNOW. maplibre has a THIRD _data
shape: updateData() stores { updateable } (maplibre-gl-dev.js:49001). No product code
calls updateData today, so this is a landmine rather than a bug -- and it is armed the
moment someone adopts partial updates for performance, at which point the product
reader would have gone back to returning [] in silence: "the map drew nothing", stated
as fact about a payload nobody recognised, one line below the url warning that exists
to prevent exactly that. Both readers now name the unrecognised shape by its keys, and
a fixture holds it, so adopting updateData() trips a test instead of blanking a map.
Negative-tested: dropping the single-Feature case, silencing either reader, or making
the gate adopt the product's url answer each turn it red; restored, 14/14 green.
check:pin-selection still passes, so the product reader is unchanged where it matters.
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