Everything a Write Must Clear Before It Starts — .datom_check_write

The one entry sequence for every write route. Ordered, and the order matters:

Usage

.datom_check_write_entry(conn, artifact = NULL)

Arguments

conn: A datom_conn object.
artifact: Name of the single artifact this write touches, or NULL to check every artifact present in the clone.

Value

Invisibly NULL. Aborts on any refusal.

Details

The floor – refuse if this repo has declared this build too old.
The manifest, read through the one shared reader, which checks the declared format and then converts an older document in memory. Refusing a format from the future has to happen before the conversion, because there is no conversion step for a version this build has never heard of.
The shape the conversion reached. If the artifact list is still absent after the chain has run, this document belongs to a lineage this build cannot produce – refuse rather than overwrite it in an older shape.
The vocabulary, on the manifest's top level, on each of its artifact entries, and on each per-artifact metadata document this write will touch.

Why step 3 is worded as "still absent after the chain" and not "absent". A current build meeting a pre-rename repo finds no artifact list either, and a rule that refused on that would deadlock the very upgrade it exists to protect: no repo could ever move forward. The discriminator is not the key, it is whether the chain can reach the shape. Note the deliberate asymmetry with the reader, which will one day rebuild on this same condition – same evidence, opposite response, because reads limp and writes stop.

Which per-artifact documents get checked depends on the route, which is why artifact exists. A table write or a metadata-only sync touches one artifact; the mirror-everything route touches all of them, and it is the route with no artifact name in its arguments at all. Both cases enumerate through .datom_clone_artifact_names(), the same helper the mirror route itself uses, so the door cannot end up inspecting a different set than the one that gets written.

Callable more than once, and one route calls it twice. Nothing here mutates anything, so re-running it is free. The metadata-only route pulls from the remote as its first act – after this check has already read the clone – so a collaborator's newer document can arrive in that pull; that route runs the sequence again afterwards. See .datom_sync_metadata().