remove FromAction interface

packages/svelte/src/attachments/index.js

@@ -1,4 +1,5 @@
-/** @import { FromAction } from './public.js' */
+/** @import { Action, ActionReturn } from 'svelte/action' */
+/** @import { Attachment } from 'svelte/attachments' */
 import { noop, render_effect } from 'svelte/internal/client';
 import { ATTACHMENT_KEY } from '../constants.js';
 import { untrack } from 'svelte';
@@ -33,17 +34,25 @@ export function createAttachmentKey() {
 /**
  * Converts an Action into an Attachment keeping the same behavior. It's useful if you want to start using
  * attachments on Components but you have library provided actions.
- * @type {FromAction}
+ *
+ * Note that the second argument, if provided, must be a function that _returns_ the argument to the
+ * action function, not the argument itself.
+ *
+ * @template {EventTarget} E
+ * @template {unknown} T
+ * @param {Action<E, T> | function(E, T): void | ActionReturn<T>} action The action function
+ * @param {() => T} [fn] A function that returns the argument for the action
+ * @returns {Attachment<E>}
  * @since 5.32
  */
-export function fromAction(action, /** @type {() => any} */ get_arg = noop) {
+export function fromAction(action, fn = /** @type {() => T} */ (noop)) {
 	return (element) => {
-		const { update, destroy } = untrack(() => action(element, get_arg()) ?? {});
+		const { update, destroy } = untrack(() => action(element, fn()) ?? {});
 
 		if (update) {
 			var ran = false;
 			render_effect(() => {
-				const arg = get_arg();
+				const arg = fn();
 				if (ran) update(arg);
 			});
 			ran = true;

packages/svelte/src/attachments/public.d.ts

@@ -11,18 +11,4 @@ export interface Attachment<T extends EventTarget = Element> {
 	(element: T): void | (() => void);
 }
 
-export interface FromAction<Element extends EventTarget = HTMLElement, Par = unknown> {
-	<Node extends Element, Parameter extends Par>(
-		...args: undefined extends NoInfer<Parameter>
-			? [
-					action: (node: Node, parameter?: never) => void | ActionReturn<Parameter>,
-					parameter?: () => NoInfer<Parameter>
-				]
-			: [
-					action: (node: Node, parameter: Parameter) => void | ActionReturn<Parameter>,
-					parameter: () => NoInfer<Parameter>
-				]
-	): Attachment<Node>;
-}
-
 export * from './index.js';

packages/svelte/types/index.d.ts

@@ -625,7 +625,7 @@ declare module 'svelte/animate' {
 }
 
 declare module 'svelte/attachments' {
-	import type { ActionReturn } from 'svelte/action';
+	import type { ActionReturn, Action } from 'svelte/action';
 	/**
 	 * An [attachment](https://svelte.dev/docs/svelte/@attach) is a function that runs when an element is mounted
 	 * to the DOM, and optionally returns a function that is called when the element is later removed.
@@ -636,20 +636,6 @@ declare module 'svelte/attachments' {
 	export interface Attachment<T extends EventTarget = Element> {
 		(element: T): void | (() => void);
 	}
-
-	export interface FromAction<Element extends EventTarget = HTMLElement, Par = unknown> {
-		<Node extends Element, Parameter extends Par>(
-			...args: undefined extends NoInfer<Parameter>
-				? [
-						action: (node: Node, parameter?: never) => void | ActionReturn<Parameter>,
-						parameter?: () => NoInfer<Parameter>
-					]
-				: [
-						action: (node: Node, parameter: Parameter) => void | ActionReturn<Parameter>,
-						parameter: () => NoInfer<Parameter>
-					]
-		): Attachment<Node>;
-	}
 	/**
 	 * Creates an object key that will be recognised as an attachment when the object is spread onto an element,
 	 * as a programmatic alternative to using `{@attach ...}`. This can be useful for library authors, though
@@ -673,49 +659,18 @@ declare module 'svelte/attachments' {
 	 * @since 5.29
 	 */
 	export function createAttachmentKey(): symbol;
-	export function fromAction<Node extends HTMLElement, Parameter extends any>(...args: undefined extends NoInfer<Parameter> ? [action: (node: Node, parameter?: never) => void | ActionReturn_1<Parameter, Record<never, any>>, parameter?: (() => NoInfer<Parameter>) | undefined] : [action: (node: Node, parameter: Parameter) => void | ActionReturn_1<Parameter, Record<never, any>>, parameter: () => NoInfer<Parameter>]): Attachment<Node>;
 	/**
-	 * Actions can return an object containing the two properties defined in this interface. Both are optional.
+	 * Converts an Action into an Attachment keeping the same behavior. It's useful if you want to start using
-	 * - update: An action can have a parameter. This method will be called whenever that parameter changes,
+	 * attachments on Components but you have library provided actions.
-	 *   immediately after Svelte has applied updates to the markup. `ActionReturn` and `ActionReturn<undefined>` both
-	 *   mean that the action accepts no parameters.
-	 * - destroy: Method that is called after the element is unmounted
-	 *
-	 * Additionally, you can specify which additional attributes and events the action enables on the applied element.
-	 * This applies to TypeScript typings only and has no effect at runtime.
 	 *
-	 * Example usage:
+	 * Note that the second argument, if provided, must be a function that _returns_ the argument to the
-	 * ```ts
+	 * action function, not the argument itself.
-	 * interface Attributes {
-	 * 	newprop?: string;
-	 * 	'on:event': (e: CustomEvent<boolean>) => void;
-	 * }
 	 *
-	 * export function myAction(node: HTMLElement, parameter: Parameter): ActionReturn<Parameter, Attributes> {
+	 * @param action The action function
-	 * 	// ...
+	 * @param fn A function that returns the argument for the action
-	 * 	return {
+	 * @since 5.32
-	 * 		update: (updatedParameter) => {...},
-	 * 		destroy: () => {...}
-	 * 	};
-	 * }
-	 * ```
 	 */
-	interface ActionReturn_1<
+	export function fromAction<E extends EventTarget, T extends unknown>(action: Action<E, T> | ((arg0: E, arg1: T) => void | ActionReturn<T>), fn?: (() => T) | undefined): Attachment<E>;
-		Parameter = undefined,
-		Attributes extends Record<string, any> = Record<never, any>
-	> {
-		update?: (parameter: Parameter) => void;
-		destroy?: () => void;
-		/**
-		 * ### DO NOT USE THIS
-		 * This exists solely for type-checking and has no effect at runtime.
-		 * Set this through the `Attributes` generic instead.
-		 */
-		$$_attributes?: Attributes;
-	}
-
-	// Implementation notes:
-	// - undefined extends X instead of X extends undefined makes this work better with both strict and nonstrict mode
 
 	export {};
 }