blog/src/content/config.ts

import { defineCollection, z } from "astro:content";

const posts = defineCollection({
  type: "content",

  // Type-check frontmatter using a schema
  schema: z.object({
    title: z.string(),
    date: z.date(),

    // Transform string to Date object
    pubDate: z
      .string()
      .or(z.date())
      .transform((val) => new Date(val))
      .optional(),
    updatedDate: z
      .string()
      .optional()
      .transform((str) => (str ? new Date(str) : undefined))
      .optional(),

    tags: z.array(z.string()),
    draft: z.boolean().default(false),
  }),
});

export const collections = { posts };