type definitions for loadAll

.changeset/poor-avocados-drop.md

@@ -0,0 +1,5 @@
+---
+'houdini-svelte': patch
+---
+
+Improve typing for loadAll

.prettierignore

@@ -1,4 +1,6 @@
 **/build/**
 README.md
 .github/**
-packages/*/package.json
+packages/*/package.json
+
+packages/houdini-svelte/src/runtime/index.ts

e2e/_api/package.json

@@ -8,11 +8,11 @@
 	"author": "",
 	"license": "ISC",
 	"dependencies": {
-		"graphql": "^15.5.0",
+		"@graphql-yoga/node": "^2.13.13",
 		"@kitql/helper": "^0.5.0",
+		"graphql": "^15.5.0",
 		"graphql-relay": "^0.10.0",
 		"graphql-ws": "^5.8.2",
-		"@graphql-yoga/node": "^2.13.13",
 		"ws": "^8.8.1"
 	}
 }

e2e/sveltekit/package.json

@@ -4,12 +4,12 @@
   "private": true,
   "type": "module",
   "scripts": {
-    "web": "cross-env TZ=utc vite dev --host 0.0.0.0",
-    "api": "cross-env e2e-api",
+    "web": "vite dev --host 0.0.0.0",
+    "api": "cross-env TZ=utc e2e-api",
     "dev": "concurrently \"pnpm run web\" \"pnpm run api\" -n \"web,api\" -c \"green,magenta\"",
     "build": "vite build",
     "package": "svelte-kit package",
-    "previewWeb": "cross-env TZ=utc vite preview --port 3007",
+    "previewWeb": "vite preview --port 3007",
     "preview": "concurrently \"pnpm run previewWeb\" \"pnpm run api\" -n \"web,api\" -c \"green,magenta\"",
     "tests": "playwright test ",
     "test": "npm run tests",

e2e/sveltekit/src/routes/stores/ssr-one-store-multivariables/+page.svelte

@@ -1,9 +1,19 @@
 <script lang="ts">
+  import { MultiUserStore } from '$houdini';
   import type { PageData } from './$types';
 
   export let data: PageData;
 
   $: ({ store1, store2 } = data);
+
+  const checkTypes = () => {
+    return (
+      `${data.store1 instanceof MultiUserStore} ` +
+      `- ${data.store2 instanceof MultiUserStore} ` +
+      // @ts-ignore
+      `- ${data.store3 instanceof MultiUserStore}`
+    );
+  };
 </script>
 
 <h1>ssr-one-store-multivariables</h1>
@@ -15,3 +25,7 @@
 <div id="result-5">
   {$store2.data?.user.id} - {$store2.data?.user.name}
 </div>
+
+<div id="result-types">
+  {checkTypes()}
+</div>

e2e/sveltekit/src/routes/stores/ssr-one-store-multivariables/spec.ts

@@ -9,4 +9,10 @@ test.describe('ssr-one-store-multivariables Page', () => {
     await expectToBe(page, 'store-multi-user:1 - Bruce Willis');
     await expectToBe(page, 'store-multi-user:5 - Will Smith', 'div[id=result-5]');
   });
+
+  test('loadAll should brings correct types', async ({ page }) => {
+    await goto(page, routes.Stores_SSR_One_Store_Multivariables);
+
+    await expectToBe(page, 'true - true - false', 'div[id=result-types]');
+  });
 });

package.json

@@ -33,7 +33,7 @@
 		"@trivago/prettier-plugin-sort-imports": "^3.3.0",
 		"eslint-plugin-unused-imports": "^2.0.0",
 		"graphql": "*",
-		"prettier": "^2.5.1",
+		"prettier": "^2.7.0",
 		"turbo": "^1.5.4",
 		"vite": "^3.1.6",
 		"vitest": "^0.23.4"

packages/houdini-svelte/src/runtime/index.ts

@@ -8,6 +8,29 @@ export * from './session'
 type LoadResult = Promise<{ [key: string]: QueryStore<any, {}> }>
 type LoadAllInput = LoadResult | Record<string, LoadResult>
 
+// gets all the values from an object
+type ValueOf<T extends Record<PropertyKey, unknown>> = T[keyof T]
+
+// transforms `A | B | C | ...` to `A & B & C & ...`
+type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) extends (k: infer I) => void
+	? I
+	: never;
+
+// transforms `LoadResult` into its awaited type
+// transforms `{a: LoadResult}` and replaces the key of the load result with `a`
+type InferLoadResult<T extends LoadAllInput> = T extends Record<infer Key, infer Res extends LoadResult> ? {
+	[K in Key]: ValueOf<Awaited<Res>>
+} : T extends LoadResult ? Awaited<T> : never
+
+export async function loadAll<
+	// generic to narrow the array correctly
+	L extends LoadAllInput,
+	// generic to get all of the inputs otherwise it fails on the `...`
+	Loads extends L[]>(
+		...loads: Loads
+	): Promise<UnionToIntersection<{
+		[K in keyof Loads]: InferLoadResult<Loads[K]>
+	}[number]>>
 // putting this here was the only way i could find to reliably avoid import issues
 // its really the only thing from lib that users should import so it makes sense to have it here....
 export async function loadAll(