v1.6.1 — a blank field is not a failed read

Found on a live REDCap 17.0.6 project while testing the 1.6.0 deployment, not by a test.

A same-form rule — both operands on the page being rendered, blockSave:"hard" — shipped as
["const", false] with deferred: true and the reason "reading its saved value failed".
Nothing had failed. Both fields were simply blank. Entering 5 against a minimum of 10
produced no verdict, no outline, and saved cleanly. Saving once so the fields held values made the
same page validate and block correctly, which is what identified the trigger.

REDCap omits a blank field from getData output, so a record whose every REQUESTED field is blank
comes back with no node at all — and readValues() read that absence as a failed read. This is
the same principle the per-field default already rests on ("absence is not, by itself, unresolvable"),
applied one level up: it was right for fields and wrong for the record node.

Two changes, because the fix must not reopen H-04 — a read that genuinely fails still must not be
judged as blank:

• The record id field is requested alongside the caller's fields. It is stored for every existing
  record and is never blank, so a returned node becomes a positive fact rather than an inference. It
  also keeps the repeat_instances buckets in the result, which is what resolveOne() needs to tell
  a genuine blank from a value on another repeating instrument — without them, a blank cross-repeat
  reference resolved as a plain blank.
• A record still absent is then read by the shape of the result: an empty result means REDCap
  holds nothing for this record, so every field is blank and every state stays ok; a result
  carrying other records but not the one asked for is anomalous and stays unreadable, as does a
  non-array result.

Scope of the defect: an existing record where every field referenced by that page's rules was
blank — typically the first pass at a form on a record created elsewhere. New records were never
affected (REDCap passes no record, so no read happens), nor were pages whose rules reference a mix of
blank and filled fields. The post-save audit was unaffected throughout, because it runs after the
write when the values exist; it logged the violation the browser had failed to block.

tests/hosting_php.php gains the H-06 section: 10 checks, 6 of which fail on 1.6.0, including both
contrast cases that must keep deferring.

---

Universal Field Validator is a REDCap external module. Rule kinds: @UVALIDATE (check-character / regex), @UVASSERT (cross-field constraints), @UVREQUIRED (conditional required), @UVUNIQUE (no duplicates across records), @UVCHOICES (dynamic choice filtering).

Docs: README · User guide · Action-tag examples · Install