Field max length

Lint rule to validate field value lengths against HL7v2 profile maxLength.

What it does

Flags field values that exceed the maxLength declared in the HL7v2 profile for the message's version. Length is computed by recursively summing the string lengths of all subcomponent values in a repetition, so delimiters (^, &, ~) are not counted. The rule reads profile context attached by @glion/annotate-profile-context and reports once per offending repetition. Fields without a declared maxLength, empty fields, and Z-segments are skipped.

Install

npm install @glion/lint-profile-field-max-length

Use

import { hl7v2AnnotateProfileContext } from "@glion/annotate-profile-context";
import { hl7v2Parser } from "@glion/parser";
import hl7v2LintFieldMaxLength from "@glion/lint-profile-field-max-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",
  "PID|1||PATID1234^^^HOSP^MR||DOE^JANE||19800101|F",
].join("\r");

const file = await unified()
  .use(hl7v2Parser)
  .use(hl7v2AnnotateProfileContext)
  .use(hl7v2LintFieldMaxLength)
  .process(message);

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

API

unified().use(hl7v2LintFieldMaxLength)

A unified lint rule plugin. Takes no options.

Reads file.data.profile. For each segment in the tree it walks its fields, looks up the profile entry by sequence, and — if a maxLength is declared — compares it against getLength() from @glion/utils for every repetition. Each repetition over the limit produces one message.

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

declare const hl7v2LintFieldMaxLength: Plugin<[], Root>;
export default hl7v2LintFieldMaxLength;

What it checks

This rule flags fields whose measured content length is greater than the maxLength declared for that field in the HL7v2 profile. In v2.5, MSH-10 (Message Control ID) has maxLength: 20.

Valid

MSH-10 carries a 9-character Message Control ID, well within the v2.5 limit of 20:

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

Invalid

MSH-10 is 28 characters long, exceeding the v2.5 limit of 20:

MSH|^~\&|SENDER|FAC|RECV|RFAC|20250601120000||ADT^A01^ADT_A01|MSG0000000000000000000000001|P|2.5
PID|1||PATID1234^^^HOSP^MR||DOE^JANE||19800101|F

Reported message:

Field MSH-10 exceeds max length of 20 (actual: 28)

One message is produced per offending repetition. Delimiters are not included in the measured length — a composite value like DOE^JANE counts as 7 characters, not 8.