Typed templates

template and data are plain strings and objects to the API. In TypeScript you can do better: give emails.send a map of template names to data types, and it will refuse a send whose data doesn't match its template.

type Templates = {
  welcome: { name: string; appName: string; loginUrl: string };
  'magic-link': { loginUrl: string; expiresInMinutes?: number };
};

await flaresend.emails.send<Templates>({
  to: 'ada@example.com',
  template: 'welcome',
  data: { name: 'Ada', appName: 'Acme', loginUrl },   // checked against Templates['welcome']
});

await flaresend.emails.send<Templates>({
  to: 'ada@example.com',
  template: 'magic-link',
  data: { name: 'Ada' },   // type error: loginUrl is missing, name doesn't exist
});

Sends without a template are still allowed with the type argument. template and data just can't be used on their own.

The RPC client works the same way:

const mail = rpcClient(env.MAILER, { project: 'acme' });
await mail.send<Templates>({ to, template: 'welcome', data: { name, appName: 'Acme', loginUrl } });

Use the built-in typesCopy Anchor Link

@flaresend/templates exports TemplateMap, the exact data types of the built-in templates, generated from their schemas. Fields with a default (like expiresInMinutes) are optional.

import type { TemplateMap } from '@flaresend/templates';

await flaresend.emails.send<TemplateMap>({
  to: 'ada@example.com',
  template: 'password-reset',
  data: { resetUrl },
});

@flaresend/templates is a package in the Flaresend repo, not on npm. Use it from apps in the same monorepo ("@flaresend/templates": "workspace:*"), or copy the types into your own map.

TemplateData<'welcome'> gives the data type of one template.

Add your custom templatesCopy Anchor Link

Custom templates live in D1, so TypeScript can't see them. Add them to the map yourself, next to the built-in ones:

import type { TemplateMap } from '@flaresend/templates';

type Templates = TemplateMap & {
  'order-shipped': { firstName: string; orderNumber: string; trackingUrl?: string };
};

The types only help at compile time. Flaresend still checks the data when you send.

TypedSendCopy Anchor Link

The input type on its own is exported as TypedSend<Map>, for helpers that build sends:

import type { TypedSend } from '@flaresend/client';

function sendLater(input: TypedSend<Templates>) {
  return flaresend.emails.send<Templates>({ ...input, scheduledAt: tomorrow() });
}

For each name K in the map, template: K requires data: Map[K]. The client itself doesn't depend on @flaresend/templates; you bring the map.