No trailing empty field

Lint rule that flags HL7v2 segments ending with one or more empty trailing fields.

What it does

For each segment, finds the index of the last non-empty field and reports a warning if any empty fields appear after it. Trailing empty fields come from stray field separators (|) at the end of a segment and should be stripped — some strict receivers reject such segments, and downstream tools may misinterpret the empty positions.

Install

npm install @glion/lint-no-trailing-empty-field

Use

import { hl7v2Parser } from "@glion/parser";
import hl7v2LintNoTrailingEmptyField from "@glion/lint-no-trailing-empty-field";
import { unified } from "unified";
import { reporter } from "vfile-reporter";

const message =
  "MSH|^~\\&|SENDER|FAC|RECV|RFAC|20250601120000||ADT^A01^ADT_A01|MSG00001|P|2.5";

const file = await unified()
  .use(hl7v2Parser)
  .use(hl7v2LintNoTrailingEmptyField)
  .process(message);

console.error(reporter([file]));

API

unified().use(hl7v2LintNoTrailingEmptyField)

A unified lint rule plugin. Takes no options.

Visits every segment node, scans its field children from the end, and reports one message per segment that has trailing empty fields. The reported position spans the first empty field to the end of the segment (including the separator after the last empty field).

import type { Plugin } from "unified";
import type { Root } from "@glion/ast";

declare const hl7v2LintNoTrailingEmptyField: Plugin<[], Root>;
export default hl7v2LintNoTrailingEmptyField;

What it checks

A segment's last field must be non-empty. Any empty fields after the last populated field are trailing and therefore flagged.

Valid

PID ends with a populated field (F):

MSH|^~\&|SENDER|FAC|RECV|RFAC|20250601120000||ADT^A01^ADT_A01|MSG00001|P|2.5
PID|1||PATID1234^^^HOSP^MR||DOE^JANE||19800101|F

Invalid

PID has two trailing empty fields after the sex component:

MSH|^~\&|SENDER|FAC|RECV|RFAC|20250601120000||ADT^A01^ADT_A01|MSG00001|P|2.5
PID|1||PATID1234^^^HOSP^MR||DOE^JANE||19800101|F||

Reported message:

Segment has 2 trailing empty fields

The count of trailing fields is interpolated with pluralization (1 trailing empty field, 2 trailing empty fields). One message is reported per offending segment.