Attachment

Attachment

File uploads are managed by @jrmc/adonis-attachment. A Lucid model declares an attachment field with @attachment({...}); uploads produce a stored file plus derived variants (thumbnails, previews, formats) driven by named converters in config/attachment.ts. Actions accept a MultipartFile from a validated form and call attachmentManager.createFromFile(file) to assign it. Storage is Drive (fs locally, S3-family in prod). URLs are pre-computed on read via a static model helper — always call it before serializing to Inertia so the frontend gets a real URL, not undefined.

Rules

• Field on model: decorate with @attachment({ preComputeUrl: false, variants: [...] }) and type as Attachment:

  @attachment({ preComputeUrl: false, variants: ['thumbnail'] })
  declare avatar: Attachment
  

  preComputeUrl: false keeps model reads cheap — URLs are computed on demand by the static helper.
• Converters live in config/attachment.ts as a keyed record. Each converter declares options (resize, format, etc.). The variant names in @attachment({ variants: [...] }) reference those keys.
• Declaration merge happens in the config file's declare module '@jrmc/adonis-attachment' block — that's how TypeScript knows variants: ['thumbnail'] is a valid key.
• Validate uploads with VineJS vine.file({...}):

  avatar: vine.file({ extnames: ['png', 'jpg', 'jpeg', 'gif'], size: 1 * 1024 * 1024 }).nullable()
  

• Persist inside an action — the action takes a MultipartFile (not HttpContext) and delegates to the manager:

  if (input.avatar) {
    input.target.avatar = await attachmentManager.createFromFile(input.avatar)
  }
  

  See [[actions-events]] for the "no HttpContext in actions" rule.
• Pre-compute URLs before serialization. Call the model's static helper on the loaded row (or list) before running the Transformer:

  await User.preComputeUrls(users)
  return inertia.render('users/index', {
    users: UserTransformer.paginate(users, meta).useVariant('forList'),
  })
  

  The Transformer variant reads the pre-computed URL from the loaded variant.
• Fallback URL: Transformers usually resolve variant.url ?? this.resource.<remoteUrl> so an externally-hosted URL (social-auth avatar, S3 direct link) works when no local upload exists.
• Drive config picks the disk (fs, s3, gcs, …). The DRIVE_DISK env var selects it.

Repo refs

• @attachment field + preComputeUrls on read: app/users/models/user.ts (avatar).
• Converters (resize / webp): config/attachment.ts.

Doc refs

• Package README — https://github.com/batosai/adonis-attachment
• AdonisJS Drive — https://docs.adonisjs.com/guides/digging-deeper/drive
• VineJS file validation — https://vinejs.dev/docs/types/file

Workflow

Add an attachment field to a model

1. Add a converter in config/attachment.ts if the format/size you need doesn't exist yet:

   converters: {
     thumbnail: { options: { resize: 300, format: 'webp' } },
     hero: { options: { resize: 1600, format: 'webp' } },
   },
   

2. Decorate the model column:

   @attachment({ preComputeUrl: false, variants: ['hero'] })
   declare cover: Attachment
   

3. Migration: add a JSON column for the attachment metadata:

   table.json('cover').nullable()
   

4. Static preComputeUrls on the model — mirror the pattern used elsewhere:

   static async preComputeUrls(rows: Post | Post[]) {
     if (Array.isArray(rows)) {
       await Promise.all(rows.map((r) => this.preComputeUrls(r)))
       return
     }
     const hero = rows.cover?.getVariant('hero')
     if (hero) await attachmentManager.computeUrl(hero)
   }
   

5. Validator: cover: vine.file({ extnames: [...], size: 5 * 1024 * 1024 }).nullable().
6. Action: input.target.cover = await attachmentManager.createFromFile(input.cover).
7. Transformer: expose the URL via a helper (coverUrl()) so consumers don't dig into the variant graph.
8. Controller: call Model.preComputeUrls(...) on the loaded rows before running the Transformer.

Change a converter

Edit config/attachment.ts. Existing uploads keep their old variant unless you re-process — there's no automatic re-render on config change.

Testing

• Use a real file fixture (small PNG) with the API client's .file(...) method.
• Fake Drive: drive.fake() in group setup — see [[testing]].
• Assert the DB row has the attachment JSON populated; assert file existence via disk.assertExists(...).

Anti-patterns

• ❌ Skipping preComputeUrls before serialization — the Transformer returns undefined for the variant URL and the frontend breaks.
• ❌ Setting preComputeUrl: true on the decorator to "save code" — every model read now does filesystem I/O, even when the row isn't serialized.
• ❌ Reading user.avatar.url directly in a React component — always through a Transformer helper. Otherwise the shape drifts.
• ❌ Storing the raw uploaded filename or path outside @attachment — the package owns storage and filenames.
• ❌ Validator without a size limit — DoS via huge uploads.
• ❌ Bypassing attachmentManager.createFromFile(...) and stuffing the MultipartFile into the model field directly.

Related skills

[[crud]] · [[actions-events]] · [[testing]] · [[inertia]]