FH04 — Array element into a scalar column

Group: Selector (schema-driven) · Severity: warning · Needs: lint --package

A scalar column’s selector reaches an array-valued element — either by landing on it (name) or by navigating through it (name.family, which is a collection across all names) — without narrowing it to one item. A scalar column expects a single value; an un-narrowed collection is flagged.

Example

name is an array on Patient; both of these trigger FH04 in a scalar column:

{
  "resource": "Patient",
  "select": [{ "column": [
    { "name": "n", "path": "name" },
    { "name": "f", "path": "name.family" }
  ] }]
}

warning [FH04] (f): navigates into an array element without narrowing; the
result is a collection (use first()/where()/an index, or mark the column collection)

Fix

Narrow the collection with first(), where(...), or an index (name.first().family, name[0].family), or set "collection": true on the column to keep the array.