Bug: ResultFormatter.temperature / totalAirTemp render "NaN degrees" for non-numeric input — only guard empty string, not NaN

[kevinelliott]

Summary

ResultFormatter.temperature (lib/utils/result_formatter.ts:331-344) and ResultFormatter.totalAirTemp (346-359) guard value.length === 0 and then run Number(value.replace('M', '-').replace('P', '+')). That guard covers the empty-string case, but any non-numeric value (which Number(...) converts to NaN) sails past it: raw.outside_air_temperature / raw.total_air_temperature are stored as NaN, and formatted.items picks up the string "NaN degrees".

This is materially the same class of bug as #494 (heading / airspeed / groundspeed / mach / day / month / arrivalDay / departureDay). #494's opening paragraph explicitly claims temperature/totalAirTemp "validate their input before pushing to formatted.items", but the if (value.length === 0) guard only handles emptiness — it does not catch NaN from a non-numeric payload. So temperature belongs on the same fix list.

Affected code

lib/utils/result_formatter.ts:331-344

static temperature(decodeResult: DecodeResult, value: string) {
  if (value.length === 0) {
    return;                                   // ← only catches empty
  }
  decodeResult.raw.outside_air_temperature = Number(
    value.replace('M', '-').replace('P', '+'),
  );                                          // ← Number('***') → NaN, stored as-is
  decodeResult.formatted.items.push({
    type: 'outside_air_temperature',
    code: 'OATEMP',
    label: 'Outside Air Temperature (C)',
    value: `${decodeResult.raw.outside_air_temperature} degrees`,   // ← "NaN degrees"
  });
}

totalAirTemp at lines 346-359 has the identical shape and the identical bug.

Reproduction

import { ResultFormatter } from './lib/utils/result_formatter';

const dr: any = { raw: {}, formatted: { items: [] } };
ResultFormatter.temperature(dr, '***');
// dr.raw.outside_air_temperature === NaN
// dr.formatted.items[0].value === 'NaN degrees'

ResultFormatter.totalAirTemp(dr, '----');
// dr.raw.total_air_temperature === NaN
// dr.formatted.items[0].value === 'NaN degrees'

Affected callers

Real call sites already in the codebase that can hit the NaN path with production-shaped payloads (ACARS carriers commonly send ***, ----, ** etc. to mean "unavailable"):

• lib/utils/arinc_702_helper.ts:188 — ResultFormatter.temperature(decodeResult, data[6]) in processPS (variant 7), no upstream validation of data[6].
• lib/utils/arinc_702_helper.ts:196 — ResultFormatter.temperature(decodeResult, data[7]) in processPS (variant 2), no upstream validation.
• lib/utils/arinc_702_helper.ts:212 — ResultFormatter.temperature(decodeResult, data[7]) in processPosition, no upstream validation.
• lib/plugins/Label_4A.ts:55 — ResultFormatter.temperature(decodeResult, fields[3]) on 4A variant-2 messages, no upstream validation.

(processPerformanceData at arinc_702_helper.ts:491-493 guards startsWith('M'/'P') || !isNaN(Number(...)) before calling, so it is already safe.)

Suggested fix

Match the pattern used by altitude (line 67-78) and by the proposed fix in #494 — add a Number.isFinite guard after the conversion so unknown values disappear from formatted.items rather than surfacing as literal "NaN":

static temperature(decodeResult: DecodeResult, value: string) {
  if (value.length === 0) return;
  const t = Number(value.replace('M', '-').replace('P', '+'));
  if (!Number.isFinite(t)) return;
  decodeResult.raw.outside_air_temperature = t;
  decodeResult.formatted.items.push({
    type: 'outside_air_temperature',
    code: 'OATEMP',
    label: 'Outside Air Temperature (C)',
    value: `${t} degrees`,
  });
}
// Same shape for totalAirTemp.

Test coverage

Add unit tests for each formatter covering the two failure modes:

• temperature(dr, '***') → no item pushed, raw.outside_air_temperature left unset
• temperature(dr, 'M25') → item pushed with value: '-25 degrees', raw.outside_air_temperature === -25
• totalAirTemp(dr, '----') → no item pushed, raw.total_air_temperature left unset
• totalAirTemp(dr, 'P12') → item pushed with value: '12 degrees'

An end-to-end test through Arinc702Helper.processPS with data[6] = '**' would also lock the fix in against the real caller.