Helper function at `src/pages/blog/_getAllPublishablePosts.ts`

_getAllPublishablePosts.ts

import { assert } from "assert-ts";
import type { MarkdownInstance, MDXInstance } from "astro";
import type { MarkdownFrontmatter } from "@data/posts/MarkdownFrontmatter";

export type MarkdownOrMDXInstance =
  | MarkdownInstance<MarkdownFrontmatter>
  | MDXInstance<MarkdownFrontmatter>;

type PartialMarkdownOrMDXInstance =
  | MarkdownInstance<Partial<MarkdownFrontmatter>>
  | MDXInstance<Partial<MarkdownFrontmatter>>;

/** getAllPublishablePosts returns all `/blog` MD and MDX posts, validated in their shape:
    all posts that have a slug and date and aren't hidden, and sort by date. */
export function getAllPublishablePosts(): MarkdownOrMDXInstance[] {
  const allMdPages = import.meta.glob("../../data/posts/*.md", {
    eager: true,
  }) as Record<string, MarkdownInstance<Partial<MarkdownFrontmatter>>>;
  const allMdxPages = import.meta.glob("../../data/posts/**/*.mdx", {
    eager: true,
  }) as Record<string, MDXInstance<Partial<MarkdownFrontmatter>>>;

  const allPages = (
    Object.values({ ...allMdPages, ...allMdxPages }) as PartialMarkdownOrMDXInstance[]
  )
    .filter(function (post): post is MarkdownOrMDXInstance {
      const missingError = (prop: string) => `post ${post.file.toString()} has no ${prop}`;
      assert(post.frontmatter.title, missingError("title"));
      assert(post.frontmatter.summary, missingError("summary"));
      assert(post.frontmatter.hero, missingError("hero"));
      assert(post.frontmatter.hero?.src, missingError("hero.src"));
      assert(post.frontmatter.hero?.alt, missingError("hero.alt"));
      return !!post.frontmatter.slug && !!post.frontmatter.date && !post.frontmatter.hide;
    })
    .sort(
      (a, b) => new Date(b.frontmatter.date).valueOf() - new Date(a.frontmatter.date).valueOf()
    );

  return allPages;
}