fix: use arrow function types over bound functions (#12955)

Using class method function types causes SvelteKit users to get TypeScript ESLint errors if they're using the [@typescript-eslint/unbound-method][1] rule (included by default in the `recommended-type-checked` config). [1]: https://typescript-eslint.io/rules/unbound-method/ The following types in `public.d.ts` are still using non-arrow functions, since - These functions are for user inputs, which might rely on these functions being bound, and so it might be a breaking change to change these types: - [`Emulator['platform']`][1] - functions in `KitConfig` - Class methods that rely on `this`: - [`Server`][2] [1]: https://github.com/sveltejs/kit/blob/b25f2d052bbf22e832ac57cbf9e12c48ac922f96/packages/kit/src/exports/public.d.ts#L272-L276 [2]: https://github.com/sveltejs/kit/blob/b25f2d052bbf22e832ac57cbf9e12c48ac922f96/packages/kit/src/exports/public.d.ts#L1174-L1178 fixes #12622

Author: aloisklink

.changeset/wet-dancers-kneel.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: use arrow function types over bound funcs

packages/kit/src/exports/public.d.ts

@@ -34,7 +34,7 @@ export interface Adapter {
  * This function is called after SvelteKit has built your app.
  * @param builder An object provided by SvelteKit that contains methods for adapting the app
  */
-adapt(builder: Builder): MaybePromise<void>;
+adapt: (builder: Builder) => MaybePromise<void>;
 /**
  * Checks called during dev and build to determine whether specific features will work in production with this adapter
  */
@@ -49,7 +49,7 @@ export interface Adapter {
  * Creates an `Emulator`, which allows the adapter to influence the environment
  * during dev, build and prerendering
  */
-emulate?(): MaybePromise<Emulator>;
+emulate?: () => MaybePromise<Emulator>;
 }
 
 export type LoadProperties<input extends Record<string, any> | void> = input extends void
@@ -94,9 +94,9 @@ export interface Builder {
 /** Print messages to the console. `log.info` and `log.minor` are silent unless Vite's `logLevel` is `info`. */
 log: Logger;
 /** Remove `dir` and all its contents. */
-rimraf(dir: string): void;
+rimraf: (dir: string) => void;
 /** Create `dir` and any required parent directories. */
-mkdirp(dir: string): void;
+mkdirp: (dir: string) => void;
 
 /** The fully resolved `svelte.config.js`. */
 config: ValidatedConfig;
@@ -111,59 +111,59 @@ export interface Builder {
  * @param fn A function that groups a set of routes into an entry point
  * @deprecated Use `builder.routes` instead
  */
-createEntries(fn: (route: RouteDefinition) => AdapterEntry): Promise<void>;
+createEntries: (fn: (route: RouteDefinition) => AdapterEntry) => Promise<void>;
 
 /**
  * Find all the assets imported by server files belonging to `routes`
  */
-findServerAssets(routes: RouteDefinition[]): string[];
+findServerAssets: (routes: RouteDefinition[]) => string[];
 
 /**
  * Generate a fallback page for a static webserver to use when no route is matched. Useful for single-page apps.
  */
-generateFallback(dest: string): Promise<void>;
+generateFallback: (dest: string) => Promise<void>;
 
 /**
  * Generate a module exposing build-time environment variables as `$env/dynamic/public`.
  */
-generateEnvModule(): void;
+generateEnvModule: () => void;
 
 /**
  * Generate a server-side manifest to initialise the SvelteKit [server](https://svelte.dev/docs/kit/@sveltejs-kit#Server) with.
  * @param opts a relative path to the base directory of the app and optionally in which format (esm or cjs) the manifest should be generated
  */
-generateManifest(opts: { relativePath: string; routes?: RouteDefinition[] }): string;
+generateManifest: (opts: { relativePath: string; routes?: RouteDefinition[] }) => string;
 
 /**
  * Resolve a path to the `name` directory inside `outDir`, e.g. `/path/to/.svelte-kit/my-adapter`.
  * @param name path to the file, relative to the build directory
  */
-getBuildDirectory(name: string): string;
+getBuildDirectory: (name: string) => string;
 /** Get the fully resolved path to the directory containing client-side assets, including the contents of your `static` directory. */
-getClientDirectory(): string;
+getClientDirectory: () => string;
 /** Get the fully resolved path to the directory containing server-side code. */
-getServerDirectory(): string;
+getServerDirectory: () => string;
 /** Get the application path including any configured `base` path, e.g. `my-base-path/_app`. */
-getAppPath(): string;
+getAppPath: () => string;
 
 /**
  * Write client assets to `dest`.
  * @param dest the destination folder
  * @returns an array of files written to `dest`
  */
-writeClient(dest: string): string[];
+writeClient: (dest: string) => string[];
 /**
  * Write prerendered files to `dest`.
  * @param dest the destination folder
  * @returns an array of files written to `dest`
  */
-writePrerendered(dest: string): string[];
+writePrerendered: (dest: string) => string[];
 /**
  * Write server-side code to `dest`.
  * @param dest the destination folder
  * @returns an array of files written to `dest`
  */
-writeServer(dest: string): string[];
+writeServer: (dest: string) => string[];
 /**
  * Copy a file or directory.
  * @param from the source file or directory
@@ -172,20 +172,20 @@ export interface Builder {
  * @param opts.replace a map of strings to replace
  * @returns an array of files that were copied
  */
-copy(
+copy: (
 from: string,
 to: string,
 opts?: {
 filter?(basename: string): boolean;
 replace?: Record<string, string>;
 }
-): string[];
+) => string[];
 
 /**
  * Compress files in `directory` with gzip and brotli, where appropriate. Generates `.gz` and `.br` files alongside the originals.
  * @param {string} directory The directory containing the files to be compressed
  */
-compress(directory: string): Promise<void>;
+compress: (directory: string) => Promise<void>;
 }
 
 export interface Config {
@@ -215,13 +215,13 @@ export interface Cookies {
  * @param name the name of the cookie
  * @param opts the options, passed directly to `cookie.parse`. See documentation [here](https://github.com/jshttp/cookie#cookieparsestr-options)
  */
-get(name: string, opts?: import('cookie').CookieParseOptions): string | undefined;
+get: (name: string, opts?: import('cookie').CookieParseOptions) => string | undefined;
 
 /**
  * Gets all cookies that were previously set with `cookies.set`, or from the request headers.
  * @param opts the options, passed directly to `cookie.parse`. See documentation [here](https://github.com/jshttp/cookie#cookieparsestr-options)
  */
-getAll(opts?: import('cookie').CookieParseOptions): Array<{ name: string; value: string }>;
+getAll: (opts?: import('cookie').CookieParseOptions) => Array<{ name: string; value: string }>;
 
 /**
  * Sets a cookie. This will add a `set-cookie` header to the response, but also make the cookie available via `cookies.get` or `cookies.getAll` during the current request.
@@ -233,11 +233,11 @@ export interface Cookies {
  * @param value the cookie value
  * @param opts the options, passed directly to `cookie.serialize`. See documentation [here](https://github.com/jshttp/cookie#cookieserializename-value-options)
  */
-set(
+set: (
 name: string,
 value: string,
 opts: import('cookie').CookieSerializeOptions & { path: string }
-): void;
+) => void;
 
 /**
  * Deletes a cookie by setting its value to an empty string and setting the expiry date in the past.
@@ -246,7 +246,7 @@ export interface Cookies {
  * @param name the name of the cookie
  * @param opts the options, passed directly to `cookie.serialize`. The `path` must match the path of the cookie you want to delete. See documentation [here](https://github.com/jshttp/cookie#cookieserializename-value-options)
  */
-delete(name: string, opts: import('cookie').CookieSerializeOptions & { path: string }): void;
+delete: (name: string, opts: import('cookie').CookieSerializeOptions & { path: string }) => void;
 
 /**
  * Serialize a cookie name-value pair into a `Set-Cookie` header string, but don't apply it to the response.
@@ -259,11 +259,11 @@ export interface Cookies {
  * @param value the cookie value
  * @param opts the options, passed directly to `cookie.serialize`. See documentation [here](https://github.com/jshttp/cookie#cookieserializename-value-options)
  */
-serialize(
+serialize: (
 name: string,
 value: string,
 opts: import('cookie').CookieSerializeOptions & { path: string }
-): string;
+) => string;
 }
 
 /**
@@ -738,7 +738,7 @@ export interface KitConfig {
  */
 export type Handle = (input: {
 event: RequestEvent;
-resolve(event: RequestEvent, opts?: ResolveOptions): MaybePromise<Response>;
+resolve: (event: RequestEvent, opts?: ResolveOptions) => MaybePromise<Response>;
 }) => MaybePromise<Response>;
 
 /**
@@ -893,14 +893,14 @@ export interface LoadEvent<
  *
  * `setHeaders` has no effect when a `load` function runs in the browser.
  */
-setHeaders(headers: Record<string, string>): void;
+setHeaders: (headers: Record<string, string>) => void;
 /**
  * `await parent()` returns data from parent `+layout.js` `load` functions.
  * Implicitly, a missing `+layout.js` is treated as a `({ data }) => data` function, meaning that it will return and forward data from parent `+layout.server.js` files.
  *
  * Be careful not to introduce accidental waterfalls when using `await parent()`. If for example you only want to merge parent data into the returned output, call it _after_ fetching your other data.
  */
-parent(): Promise<ParentData>;
+parent: () => Promise<ParentData>;
 /**
  * This function declares that the `load` function has a _dependency_ on one or more URLs or custom identifiers, which can subsequently be used with [`invalidate()`](https://svelte.dev/docs/kit/$app-navigation#invalidate) to cause `load` to rerun.
  *
@@ -938,7 +938,7 @@ export interface LoadEvent<
  * <button on:click={increase}>Increase Count</button>
  * ```
  */
-depends(...deps: Array<`${string}:${string}`>): void;
+depends: (...deps: Array<`${string}:${string}`>) => void;
 /**
  * Use this function to opt out of dependency tracking for everything that is synchronously called within the callback. Example:
  *
@@ -952,7 +952,7 @@ export interface LoadEvent<
  * }
  * ```
  */
-untrack<T>(fn: () => T): T;
+untrack: <T>(fn: () => T) => T;
 }
 
 export interface NavigationEvent<
@@ -1047,7 +1047,7 @@ export interface BeforeNavigate extends Navigation {
 /**
  * Call this to prevent the navigation from starting.
  */
-cancel(): void;
+cancel: () => void;
 }
 
 /**
@@ -1161,7 +1161,7 @@ export interface RequestEvent<
 /**
  * The client's IP address, set by the adapter.
  */
-getClientAddress(): string;
+getClientAddress: () => string;
 /**
  * Contains custom data that was added to the request within the [`server handle hook`](https://svelte.dev/docs/kit/hooks#Server-hooks-handle).
  */
@@ -1209,7 +1209,7 @@ export interface RequestEvent<
  *
  * You cannot add a `set-cookie` header with `setHeaders` — use the [`cookies`](https://svelte.dev/docs/kit/@sveltejs-kit#Cookies) API instead.
  */
-setHeaders(headers: Record<string, string>): void;
+setHeaders: (headers: Record<string, string>) => void;
 /**
  * The requested URL.
  */
@@ -1242,20 +1242,20 @@ export interface ResolveOptions {
  * but they will always be split at sensible boundaries such as `%sveltekit.head%` or layout/page components.
  * @param input the html chunk and the info if this is the last chunk
  */
-transformPageChunk?(input: { html: string; done: boolean }): MaybePromise<string | undefined>;
+transformPageChunk?: (input: { html: string; done: boolean }) => MaybePromise<string | undefined>;
 /**
  * Determines which headers should be included in serialized responses when a `load` function loads a resource with `fetch`.
  * By default, none will be included.
  * @param name header name
  * @param value header value
  */
-filterSerializedResponseHeaders?(name: string, value: string): boolean;
+filterSerializedResponseHeaders?: (name: string, value: string) => boolean;
 /**
  * Determines what should be added to the `<head>` tag to preload it.
  * By default, `js` and `css` files will be preloaded.
  * @param input the type of the file and its path
  */
-preload?(input: { type: 'font' | 'css' | 'js' | 'asset'; path: string }): boolean;
+preload?: (input: { type: 'font' | 'css' | 'js' | 'asset'; path: string }) => boolean;
 }
 
 export interface RouteDefinition<Config = any> {
@@ -1297,7 +1297,7 @@ export interface SSRManifest {
 client: NonNullable<BuildData['client']>;
 nodes: SSRNodeLoader[];
 routes: SSRRoute[];
-matchers(): Promise<Record<string, ParamMatcher>>;
+matchers: () => Promise<Record<string, ParamMatcher>>;
 /** A `[file]: size` map of all assets imported by server code */
 server_assets: Record<string, number>;
 };
@@ -1324,7 +1324,7 @@ export interface ServerLoadEvent<
  *
  * Be careful not to introduce accidental waterfalls when using `await parent()`. If for example you only want to merge parent data into the returned output, call it _after_ fetching your other data.
  */
-parent(): Promise<ParentData>;
+parent: () => Promise<ParentData>;
 /**
  * This function declares that the `load` function has a _dependency_ on one or more URLs or custom identifiers, which can subsequently be used with [`invalidate()`](https://svelte.dev/docs/kit/$app-navigation#invalidate) to cause `load` to rerun.
  *
@@ -1362,7 +1362,7 @@ export interface ServerLoadEvent<
  * <button on:click={increase}>Increase Count</button>
  * ```
  */
-depends(...deps: string[]): void;
+depends: (...deps: string[]) => void;
 /**
  * Use this function to opt out of dependency tracking for everything that is synchronously called within the callback. Example:
  *
@@ -1376,7 +1376,7 @@ export interface ServerLoadEvent<
  * }
  * ```
  */
-untrack<T>(fn: () => T): T;
+untrack: <T>(fn: () => T) => T;
 }
 
 /**
@@ -1447,7 +1447,7 @@ export type SubmitFunction<
 formElement: HTMLFormElement;
 controller: AbortController;
 submitter: HTMLElement | null;
-cancel(): void;
+cancel: () => void;
 }) => MaybePromise<
 | void
 | ((opts: {
@@ -1460,7 +1460,7 @@ export type SubmitFunction<
  * @param options Set `reset: false` if you don't want the `<form>` values to be reset after a successful submission.
  * @param invalidateAll Set `invalidateAll: false` if you don't want the action to call `invalidateAll` after submission.
  */
-update(options?: { reset?: boolean; invalidateAll?: boolean }): Promise<void>;
+update: (options?: { reset?: boolean; invalidateAll?: boolean }) => Promise<void>;
  }) => void)
 >;
 

packages/kit/src/runtime/server/cookie.js

@@ -55,7 +55,7 @@ export function get_cookies(request, url, trailing_slash) {
 
 /**
  * @param {string} name
- * @param {import('cookie').CookieParseOptions} opts
+ * @param {import('cookie').CookieParseOptions} [opts]
  */
 get(name, opts) {
 const c = new_cookies[name];
@@ -91,7 +91,7 @@ export function get_cookies(request, url, trailing_slash) {
 },
 
 /**
- * @param {import('cookie').CookieParseOptions} opts
+ * @param {import('cookie').CookieParseOptions} [opts]
  */
 getAll(opts) {
 const cookies = parse(header, { decode: opts?.decode });