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 name.length !== 3. The reported text names how many characters to add or remove to reach the three-character target.

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:

Unexpected 4 header length, expected 3 characters, remove 1 character

A two-character segment name:

MS|^~\&|...

Reported message:

Unexpected 2 header length, expected 3 characters, add 1 character

The delta between the actual length and three is interpolated with pluralization (remove 1 character, add 2 characters). One message is reported per offending segment.

Segment header length

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