Segment header length

Lint rule that flags HL7v2 segment headers whose name is not exactly three characters.

What it does

Visits every segment node and checks that node.name.length === 3. HL7v2 segments are identified by a three-character code (MSH, PID, OBX, ZAD). Lengths other than three usually indicate a typo (PID1, MS, Obx), malformed input, or a miscoded private extension.

Install

npm install @glion/lint-segment-header-length

Use

import { hl7v2Parser } from "@glion/parser";
import hl7v2LintSegmentHeaderLength from "@glion/lint-segment-header-length";
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(hl7v2LintSegmentHeaderLength)
  .process(message);

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

API

`unified().use(hl7v2LintSegmentHeaderLength)`

A unified lint rule plugin. Takes no options.

Visits every segment node and reports one message per segment whose Segment ID is not three characters long, with actual set to the Segment ID.

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

declare const hl7v2LintSegmentHeaderLength: Plugin<[], Root>;
export default hl7v2LintSegmentHeaderLength;

What it checks

Each segment name must be exactly three characters long.

Valid

All segments have three-character names:

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

Invalid

A four-character segment name:

PID1|1||PATID1234^^^HOSP^MR||DOE^JANE||19800101|F

Reported message:

The Segment ID is 4 characters long; a Segment ID must be exactly 3 characters.

A two-character segment name:

MS|^~\&|...

Reported message:

The Segment ID is 2 characters long; a Segment ID must be exactly 3 characters.

A segment with an empty Segment ID, such as a line that starts with the field separator, is reported as:

The segment has an empty Segment ID; a Segment ID must be exactly 3 characters.

One message is reported per offending segment.

Segment header length

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