Prerender

import { Prerender } from "svelte-effect-runtime";

declare const Prerender:
  & (<Output, ErrorType, Requirements>(
    fn: () => Effect.Effect<Output, ErrorType, Requirements>,
    options?: {
      inputs?: (
        event: RequestEventService,
      ) => AsyncIterable<void> | Iterable<void>;
      dynamic?: boolean;
    },
  ) => EffectPrerenderFunction<void, Output, ErrorType>)
  & (<Input, Output, ErrorType, Requirements>(
    validate: "unchecked",
    fn: (arg: Input) => Effect.Effect<Output, ErrorType, Requirements>,
    options?: {
      inputs?: (
        event: RequestEventService,
      ) => AsyncIterable<Input> | Iterable<Input>;
      dynamic?: boolean;
    },
  ) => EffectPrerenderFunction<Input, Output, ErrorType>)
  & (<SchemaType extends EffectSchema, Output, ErrorType, Requirements>(
    validate: SchemaType,
    fn: (
      arg: SchemaOutput<SchemaType>,
    ) => Effect.Effect<Output, ErrorType, Requirements>,
    options?: {
      inputs?: (
        event: RequestEventService,
      ) =>
        | AsyncIterable<SchemaInput<SchemaType>>
        | Iterable<SchemaInput<SchemaType>>;
      dynamic?: boolean;
    },
  ) => EffectPrerenderFunction<SchemaInput<SchemaType>, Output, ErrorType>);

The prerender function is similar to query, except that it will be invoked at build time to prerender the result. Use this for data that changes at most once per redeployment.

import { Effect } from "effect";
import { Prerender } from "svelte-effect-runtime";
import { Database } from "$lib/server/database";

export const get_posts = Query(Effect.gen(function* () {
  const db = yield* Database;

  return yield* Database.sql`
    select title, slug
		from post
		order by published_at
		desc
	`;
}));

Prerender arguments

As with queries, prerender functions can accept an argument, which should be validated with an Effect schema:

export const get_post_by_slug = Query(
  Effect.Struct({
    slug: Effect.String,
  }),
  Effect.gen(function* () {
    const db = yield* Database;

    const [post] = yield* db.sql`
      select * from post
      where slug = ${slug}
    `;

    return yield* pipe(
      post,
      Option.fromNullable,
      Option.match({
        onNone: () => Effect.fail(new Error("Post not found")),
        onSome: (post) => post,
      }),
    );
  }),
);

Any calls to get_post(...) found by SvelteKit's crawler while prerendering pages will be saved automatically, but you can also specify which values it should be called with using the inputs option:

export const get_post = Prerender(
  Effect.Struct({
    slug: Effect.String,
  }),
  async (slug) => {/* ... */},
  {
    inputs: () => [
      "first-post",
      "second-post",
      "third-post",
    ],
  },
);