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$trace

$trace(value?, label, projection?) -> value
Compact type signature<x-sx?:x>

If value is omitted, the current context value is used.

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Diagnostics And Errors

Source: FUME

Documentation​

Emits a trace diagnostic entry and returns the original value unchanged.

Use $trace() when you want to inspect a value without changing the result flow. This helper belongs to Diagnostics And Errors: it traces execution, but it does not stop evaluation.

The second argument is the trace label. FUME stringifies that label and stores a diagnostic entry with code F5600, the current executionId, the original value, and a rendered message in the form label: projection. If you omit the optional third argument, the traced projection is the same value that gets returned. If you provide a third argument, it changes only the diagnostic message; the function still returns the original first argument.

During verbose evaluation, trace entries are collected under diagnostics.debug. If logging is enabled for that severity, FUME also writes the rendered trace message through the configured logger's debug() method.

Examples​

Emit a trace event and return the original value​

This function has a side effect (emits a trace entry), but it returns the input value. The emitted trace entry is described in prose here rather than shown as fake captured logger output.

Input

This example uses the patient-summary example input. The expression reads patientId, emits a trace entry, and returns the value.

Example input

JSON
{
  "patientId": "pat-0001",
  "name": {
    "given": "Avery",
    "family": "Reed",
    "display": "Avery Reed"
  },
  "birthDate": "1990-06-12",
  "sex": "female",
  "primaryCareTeam": {
    "organization": "ExampleCare",
    "facility": "ExampleCare Clinic",
    "practitioner": {
      "practitionerId": "prac-4001",
      "display": "Jordan Kim"
    }
  },
  "identifiers": {
    "memberId": "mbr-3001",
    "recordNumber": "rec-5001"
  },
  "tags": [
    "demo",
    "fictional"
  ],
  "_xmlTagName": "patientSummary"
}

Expression

$trace(patientId, "patientId")

Result

"pat-0001"