Function parse_migrate_layout_options 

pub fn parse_migrate_layout_options(
    value: &Value,
) -> Result<LayoutMigrationOptions, OptionsError>

Builds LayoutMigrationOptions from the JSON document migrateLayout() takes — the TS LayoutMigrationOptions, member for member, plus the lock of open() so a host that has to wait differently for the writer lock can say so. Every member is optional; {} and null both mean “move it into the nested arrangement, keeping the document’s name”.

Neither pair of document names is resolved here, for the same reason parse_layout resolves nothing: whether the two names of a pair agree is the engine’s refusal to make, so it reads the same however a caller reaches it.