Prettify middleware result types

The middleware result type was an opaque intersection chain like
`FetchStore & { contents: ... } & { stats: ... }` which was hard to read
in tooltips and error messages. This collapses the store's
`get`/`getRange` back into `AsyncReadable<O>` and shows only the
middleware extensions separately, so the result reads as
`AsyncReadable<RequestInit> & { contents: ..., stats: ... }`.

If the store or any middleware provides a concrete `getRange`, the
collapsed type uses `Required<AsyncReadable<O>>` to preserve the
non-optional guarantee. A store that only has `get` shows the default
`AsyncReadable<O>` with `getRange?` optional.

Author: manzt

packages/zarrita/__tests__/middleware-types.test.ts

@@ -23,7 +23,10 @@ describe("storeFrom", () => {
 		);
 		expectType(store).toMatchInlineSnapshot(`
 			Promise<
-				zarr.FetchStore & { stats: Readonly<zarr.RangeBatchingStats> }
+				Required<AsyncReadable<RequestInit>> & {
+					stats: Readonly<zarr.RangeBatchingStats>;
+					url: string | URL;
+				}
 			>
 		`);
 	});
@@ -38,9 +41,11 @@ describe("storeFrom", () => {
 		}
 		expectType(check).toMatchInlineSnapshot(`
 			() => Promise<
-				zarr.FetchStore & {
+				Required<AsyncReadable<RequestInit>> & {
+					stats: Readonly<zarr.RangeBatchingStats>;
+					url: string | URL;
 					contents: () => { path: AbsolutePath; kind: "array" | "group" }[];
-				} & { stats: Readonly<zarr.RangeBatchingStats> }
+				}
 			>
 		`);
 	});
@@ -62,7 +67,12 @@ describe("defineStoreMiddleware", () => {
 		);
 		let store = withCustom(new zarr.FetchStore(""), { flag: true });
 		expectType(store).toMatchInlineSnapshot(
-			`zarr.FetchStore & { hello: () => string }`,
+			`
+			Required<AsyncReadable<RequestInit>> & {
+				url: string | URL;
+				hello: () => string;
+			}
+		`,
 		);
 	});
 
@@ -88,7 +98,12 @@ describe("defineStoreMiddleware", () => {
 			retries: 5,
 		});
 		expectType(store).toMatchInlineSnapshot(
-			`zarr.FetchStore & { retries: number }`,
+			`
+			Required<AsyncReadable<RequestInit>> & {
+				url: string | URL;
+				retries: number;
+			}
+		`,
 		);
 	});
 
@@ -119,8 +134,10 @@ describe("defineStoreMiddleware", () => {
 		);
 		let store = withB(withA(new zarr.FetchStore(""), { a: 1 }), { b: "x" });
 		expectType(store).toMatchInlineSnapshot(`
-			zarr.FetchStore & { methodA: () => number } & {
+			Required<AsyncReadable<RequestInit>> & {
+				url: string | URL;
 				methodB: () => string;
+				methodA: () => number;
 			}
 		`);
 	});

packages/zarrita/src/index.ts

@@ -1,7 +1,7 @@
 // re-export all the storage interface types
 export type * from "@zarrita/storage";
 // re-export fetch store from storage
-export { default as FetchStore } from "@zarrita/storage/fetch";
+export { FetchStore, FileSystemStore } from "@zarrita/storage";
 // core
 export { registry } from "./codecs.js";
 export { create } from "./create.js";

packages/zarrita/src/middleware/define.ts

@@ -33,10 +33,22 @@ type InferStoreOpts<S> = S extends { get(key: any, opts?: infer O): any }
 	: unknown;
 
 /** If factory returns a Promise, wrap the result in Promise; otherwise keep it sync. */
+type Prettify<T> = { [K in keyof T]: T[K] } & {};
+
+/** Collapse get/getRange into AsyncReadable<O>, show extras separately. */
+type CollapseStore<T> =
+	T extends AsyncReadable<infer O>
+		? // biome-ignore lint/suspicious/noExplicitAny: needed for getRange optionality check
+			(T extends { getRange: (...args: any[]) => any }
+				? Required<AsyncReadable<O>>
+				: AsyncReadable<O>) &
+				Prettify<Omit<T, keyof AsyncReadable>>
+		: T;
+
 type WrapperResult<Ext, S> =
 	Ext extends Promise<infer Inner>
-		? Promise<S & Extensions<Inner>>
-		: S & Extensions<Ext>;
+		? Promise<CollapseStore<S & Extensions<Inner>>>
+		: CollapseStore<S & Extensions<Ext>>;
 
 function createProxy(
 	store: object,