ModalSubmitInteraction field component.attachments may be undefined despite typings

[The-LukeZ]

Which package is this bug report for?

discord.js

Issue description

When iterating over fields in a ModalSubmitInteraction, the following TypeScript code can potentially throw an error:

// ctx is a ModalSubmitInteraction
for (const field of ctx.fields.components.filter((c) => c.type === ComponentType.Label)) {
  const component = field.component;
  if (component.type === ComponentType.FileUpload) {
    const fieldAttachments = component.attachments.values().toArray() || [];
    // do something
  }
}

The issue is that component.attachments can be undefined, but the typings do not reflect this possibility. As a result, accessing component.attachments.values() without an existence check can cause a runtime error. A workaround is to use optional chaining: component.attachments?.values().

Expected behavior: The typings should indicate that attachments may be undefined.

Actual behavior: No type error occurs, leading to a possible uncaught exception at runtime.

Suggested fix: Make the type for attachments possibly undefined.

Note: Yes, I could technically use .getUploadedFiles() but for the nature of my project I can't really do this...

Code sample

// ctx is a ModalSubmitInteraction
for (const field of ctx.fields.components.filter((c) => c.type === ComponentType.Label)) {
  const comp = field.component;
  if (comp.type === ComponentType.FileUpload) {
    const fieldAttachments = comp.attachments.values().toArray() || [];
    // do something
}

// workaround:
const fieldAttachments = comp.attachments?.values().toArray() || [];

Versions

• discord.js: 14.25.1
• bun: 1.3.2
• typescript: 5.9.2
• OS:
  • Development: macOS Tahoe 26.1
  • Prod: Linux Ubuntu 24.04

Issue priority

Medium (should be fixed soon)

Which partials do you have configured?

ThreadMember

Which gateway intents are you subscribing to?

Guilds, GuildMembers, GuildModeration, GuildIntegrations, GuildWebhooks, GuildMessages, MessageContent

I have tested this issue on a development release

No response

[Jiralite]

What is in your modal?

[The-LukeZ]

My users customize this themselves. But from what I can tell there should have been

• text input (required)
• string select (required)
• file upload (optional)
• text input (optional)

[Jiralite]

As a result, accessing component.attachments.values() without an existence check can cause a runtime error.

So did you get one? Can you provide it?

[The-LukeZ]

yes: https://lukez-dev.sentry.io/share/issue/1450dd33dd8743fabd74b4b93f0c59f1/

Please note, that I updated the djs version later to ensure the correct typings are present.

[Jiralite]

Are you truncating the stack trace? Have you set it up improperly in Sentry? It only gives 2 lines and nothing about discord.js, which is useless:

TypeError: undefined is not an object (evaluating 'comp.attachments.values')
    at handleFormSubmit (/app/src/utils/ticketCreate.ts:161:27)
    at processTicksAndRejections (native:7:39)

Regardless, managed to find a reproduction:

1. Create a modal with an optional file upload component
2. Submit it
3. Check for the label component's resolved data (attachments)

[The-LukeZ]

Have you set it up improperly in Sentry?

Because I use bun, I didn't find a way to upload sourcemaps yet sadly due to the nature of bun (it transpiles TS to JS itelf and I can't execute a command for uploading sourcemaps between build and running)

[Jiralite]

Understood, to be fair, I'm not that versed in Bun. Also, thank you for reporting this!

[The-LukeZ]

haha thanks

btw what is the "Good first issue" label for? it's certainly not my first issue I created 🤔

[Jiralite]

https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/encouraging-helpful-contributions-to-your-project-with-labels

Basically, it means this is a good first issue for new contributors here.

[The-LukeZ]

ah, thanks ^^