Bug: Label_2P_FM4 splits header on `'FM4'` (no trailing space) unlike FM3/FM5, leaving a leading space in `departure_icao`

[kevinelliott]

Summary

Label_2P_FM4 splits its header on the token 'FM4', while the sibling plugins Label_2P_FM3 and Label_2P_FM5 split on 'FM3 ' and 'FM5 ' respectively (with a trailing space). Because FM4 lacks the trailing space and does not trim() the result, header[1] retains a leading space for the common FM4 <ICAO>,... header form, and that space is written straight into decodeResult.raw.departure_icao.

Location

lib/plugins/Label_2P_FM4.ts:24

const parts = message.text.split(',');

if (parts.length === 10) {
  const header = parts[0].split('FM4');   // FM3 uses 'FM3 ', FM5 uses 'FM5 '
  if (header.length < 2) {
    ...
  }
  if (header[0].length > 0) {
    ResultFormatter.unknown(decodeResult, header[0].substring(0, 4));
    ResultFormatter.flightNumber(decodeResult, header[0].substring(4));
  }
  ResultFormatter.departureAirport(decodeResult, header[1]);   // ← ' KIAD', not 'KIAD'
  ...
}

Compare with Label_2P_FM3.ts:25 (split('FM3 ')) and Label_2P_FM5.ts:24 (split('FM5 ')) — both use the space-terminated token, so header[1] starts cleanly on the ICAO.

Reproduction

const msg = {
  label: '2P',
  text: 'FM4 KIAD,OMAA,140256,1448, 39.43,- 75.62,23228,328,  43.5, 72500',
};
const result = new Label_2P_FM4().decode(msg);
// Actual:   result.raw.departure_icao === ' KIAD'
// Expected: result.raw.departure_icao === 'KIAD'

Impact

• Downstream consumers keying off departure_icao won't match a leading-space value against normal 4-char ICAOs; the airport is effectively lost.
• Any header without a trailing space (FM4KIAD,...) is still handled correctly by split('FM4 '), since the missing-header guard (header.length < 2) would then flag it as undecodable — the same behavior the FM3/FM5 siblings already have.

Suggested fix

Split on 'FM4 ' to match FM3/FM5:

const header = parts[0].split('FM4 ');

Add a test case with an FM4 <ICAO>,... input asserting raw.departure_icao === '<ICAO>' (no leading space).

Related

• Bug: Label_2P_FM3 / FM4 / FM5 missing-header guard is dead (split.length is never 0); FM3 then throws on header[1].length, FM4/FM5 emit undefined fields #462 (fixed the dead .length == 0 guard here, but did not touch the split-token inconsistency)
• Fix dead missing-preamble guard in Label_2P_FM3/FM4/FM5 #465 (companion PR)