Spots: a corrupt NZB is a result, not a reason to read the listing again

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/services/SpotService.ts

@@ -31,6 +31,9 @@ const MAX_IMAGE_SEGMENTS = 10
 /** A claimed spot whose worker died is taken again after this long. */
 const RECLAIM_AFTER = '1 hour'
 
+/** The NZB's articles were read, but they don't decode to an NZB (e.g. "invalid code lengths set"). */
+export class NzbUnreadable extends Error {}
+
 /**
  * A spot's title: from its XML, which is decoded properly (the Subject of a
  * raw header is read as ISO-8859-1), else from the header.
@@ -333,10 +336,17 @@ class SpotService {
       try {
         nzbXml = await this.readNzb(head)
       } catch (error: any) {
-        if (!/^4\d\d/.test(String(error.message))) throw error
-        // The NZB's articles are gone: the listing can't be downloaded any more.
-        update.error = 'NZB articles gone'
-        outcome = 'nzb-gone'
+        if (error instanceof NzbUnreadable) {
+          // Corrupt: reading it again won't help (LOG.md 2026-10-08 (12)).
+          update.error = `NZB unreadable: ${error.message}`.slice(0, 500)
+          outcome = 'nzb-unreadable'
+        } else if (/^4\d\d/.test(String(error.message))) {
+          // The NZB's articles are gone: the listing can't be downloaded any more.
+          update.error = 'NZB articles gone'
+          outcome = 'nzb-gone'
+        } else {
+          throw error
+        }
       }
       const nzb = nzbXml ? parseNzb(nzbXml) : null
       if (nzb && nzb.files.length > 0 && isDummyNzb(nzb, head.header.size)) {
@@ -405,7 +415,11 @@ class SpotService {
     if (segments.length === 0 || segments.length > MAX_NZB_SEGMENTS) return null
     const bodies = []
     for (const id of segments) bodies.push(await this.fetch(`BODY <${id.replace(/^<|>$/g, '')}>`))
-    return decodeSpotBinary(bodies).toString('utf8')
+    try {
+      return decodeSpotBinary(bodies).toString('utf8')
+    } catch (error: any) {
+      throw new NzbUnreadable(String(error.message))
+    }
   }
 
   /** Downloads the spot's compressed NZB and imports it as a release (D26). */

tests/functional/spot_listing.spec.ts

@@ -2,7 +2,7 @@ import { test } from '@japa/runner'
 import { createHash } from 'node:crypto'
 import db from '@adonisjs/lucid/services/db'
 import testUtils from '@adonisjs/core/services/test_utils'
-import SpotService, { isDummyNzb } from '#services/SpotService'
+import SpotService, { isDummyNzb, NzbUnreadable } from '#services/SpotService'
 import SearchService from '#services/SearchService'
 
 test.group('SpotService listings', (group) => {
@@ -117,7 +117,7 @@ test.group('SpotService reading listings', (group) => {
 <segments><segment bytes="${bytes}" number="1">a1@x</segment></segments></file></nzb>`
 
   /** A listed spot, as worker:spots leaves an old one, with its article and NZB as given. */
-  async function listedSpot(id: string, read: { description?: string; nzb?: string | null; error?: string }) {
+  async function listedSpot(id: string, read: { description?: string; nzb?: string | null; error?: string; nzbError?: Error }) {
     await db.table('spots').insert({
       message_id: id, group_name: 'free.pt', article_number: 1, title: `Listed ${id}`, poster: 'Bart', key_id: 7, size: 700_000_000,
       posted_at: new Date('2019-05-01T12:00:00Z'), verified: true, created_at: new Date(), status: 'pending',
@@ -129,7 +129,10 @@ test.group('SpotService reading listings', (group) => {
       if (read.error) throw new Error(read.error)
       return { header: { size: 700_000_000 }, xml: { description: read.description ?? '', nzbSegments: ['n@x'] } }
     }
-    service.readNzb = async () => read.nzb ?? null
+    service.readNzb = async () => {
+      if (read.nzbError) throw read.nzbError
+      return read.nzb ?? null
+    }
   }
 
   const restore = () => {
@@ -179,5 +182,12 @@ test.group('SpotService reading listings', (group) => {
     await listedSpot('l6@spot.net', { error: '430 No Such Article' })
     assert.deepEqual(await SpotService.readListings(10, 1), { gone: 1 })
     assert.isNotNull((await db.from('spots').where('message_id', 'l6@spot.net').first()).nzb_read_at)
+
+    // A corrupt NZB is a result, not something to read again.
+    await listedSpot('l7@spot.net', { nzbError: new NzbUnreadable('invalid code lengths set') })
+    assert.deepEqual(await SpotService.readListings(10, 1), { 'nzb-unreadable': 1 })
+    const l7 = await db.from('spots').where('message_id', 'l7@spot.net').first()
+    assert.isNotNull(l7.nzb_read_at)
+    assert.equal(l7.error, 'NZB unreadable: invalid code lengths set')
   })
 })