tidy up a bit

packages/svelte/src/internal/client/dom/blocks/html.js

@@ -1,9 +1,6 @@
-import { derived } from '../../reactivity/deriveds.js';
-import { block, branch, destroy_effect, render_effect } from '../../reactivity/effects.js';
-import { get } from '../../runtime.js';
-import { is_array } from '../../utils.js';
-import { hydrate_nodes, hydrate_start, hydrating } from '../hydration.js';
-import { create_fragment_from_html, remove } from '../reconciler.js';
+import { block, branch, destroy_effect } from '../../reactivity/effects.js';
+import { get_start, hydrate_nodes, hydrating } from '../hydration.js';
+import { create_fragment_from_html } from '../reconciler.js';
 import { assign_nodes } from '../template.js';
 
 /**
@@ -31,10 +28,7 @@ export function html(anchor, get_value, svg, mathml) {
 
 		effect = branch(() => {
 			if (hydrating) {
-				assign_nodes(
-					hydrate_start.previousSibling ?? hydrate_start,
-					hydrate_nodes[hydrate_nodes.length - 1]
-				);
+				assign_nodes(get_start(), hydrate_nodes[hydrate_nodes.length - 1]);
 				return;
 			}
 
@@ -66,48 +60,3 @@ export function html(anchor, get_value, svg, mathml) {
 		});
 	});
 }
-
-/**
- * Creates the content for a `@html` tag from its string value,
- * inserts it before the target anchor and returns the new nodes.
- * @template V
- * @param {Element | Text | Comment} anchor
- * @param {V} value
- * @param {boolean} svg
- * @param {boolean} mathml
- * @returns {Element | Comment | (Element | Comment | Text)[]}
- */
-function html_to_dom(anchor, value, svg, mathml) {
-	if (hydrating) return hydrate_nodes;
-
-	var html = value + '';
-	if (svg) html = `<svg>${html}</svg>`;
-	else if (mathml) html = `<math>${html}</math>`;
-
-	// Don't use create_fragment_with_script_from_html here because that would mean script tags are executed.
-	// @html is basically `.innerHTML = ...` and that doesn't execute scripts either due to security reasons.
-	/** @type {DocumentFragment | Element} */
-	var node = create_fragment_from_html(html);
-
-	if (svg || mathml) {
-		node = /** @type {Element} */ (node.firstChild);
-	}
-
-	if (node.childNodes.length === 1) {
-		var child = /** @type {Text | Element | Comment} */ (node.firstChild);
-		anchor.before(child);
-		return child;
-	}
-
-	var nodes = /** @type {Array<Text | Element | Comment>} */ ([...node.childNodes]);
-
-	if (svg || mathml) {
-		while (node.firstChild) {
-			anchor.before(node.firstChild);
-		}
-	} else {
-		anchor.before(node);
-	}
-
-	return nodes;
-}

packages/svelte/src/internal/client/dom/hydration.js

@@ -30,6 +30,17 @@ export function set_hydrate_nodes(nodes) {
 	hydrate_start = nodes && nodes[0];
 }
 
+/**
+ * When assigning nodes to an effect during hydration, we typically want the hydration boundary comment node
+ * immediately before `hydrate_start`. In some cases, this comment doesn't exist because we optimized it away.
+ * TODO it might be worth storing this value separately rather than retrieving it with `previousSibling`
+ */
+export function get_start() {
+	return /** @type {import('#client').TemplateNode} */ (
+		hydrate_start.previousSibling ?? hydrate_start
+	);
+}
+
 /**
  * This function is only called when `hydrating` is true. If passed a `<!--[-->` opening
  * hydration marker, it finds the corresponding closing marker and sets `hydrate_nodes`

packages/svelte/src/internal/client/dom/template.js

@@ -1,4 +1,4 @@
-import { hydrate_nodes, hydrate_start, hydrating } from './hydration.js';
+import { get_start, hydrate_nodes, hydrate_start, hydrating } from './hydration.js';
 import { empty } from './operations.js';
 import { create_fragment_from_html } from './reconciler.js';
 import { current_effect } from '../runtime.js';
@@ -11,18 +11,16 @@ import { queue_micro_task } from './task.js';
 
 /**
  *
- * @param {import('#client').TemplateNode | null | undefined} start
+ * @param {import('#client').TemplateNode | undefined | null} start
  * @param {import('#client').TemplateNode} end
  */
 export function assign_nodes(start, end) {
 	const effect = /** @type {import('#client').Effect} */ (current_effect);
 
 	if (effect.nodes === null) {
-		effect.nodes = { start, end };
-	} else {
-		if (effect.nodes.start === undefined) {
-			effect.nodes.start = start;
-		}
+		effect.nodes = { start, anchor: null, end };
+	} else if (effect.nodes.start === undefined) {
+		effect.nodes.start = start;
 	}
 }
 
@@ -44,10 +42,7 @@ export function template(content, flags) {
 
 	return () => {
 		if (hydrating) {
-			assign_nodes(
-				hydrate_start.previousSibling ?? hydrate_start,
-				hydrate_nodes[hydrate_nodes.length - 1]
-			);
+			assign_nodes(get_start(), hydrate_nodes[hydrate_nodes.length - 1]);
 
 			return hydrate_start;
 		}
@@ -121,10 +116,7 @@ export function ns_template(content, flags, ns = 'svg') {
 
 	return () => {
 		if (hydrating) {
-			assign_nodes(
-				hydrate_start.previousSibling ?? hydrate_start,
-				hydrate_nodes[hydrate_nodes.length - 1]
-			);
+			assign_nodes(get_start(), hydrate_nodes[hydrate_nodes.length - 1]);
 
 			return hydrate_start;
 		}
@@ -254,10 +246,7 @@ export function text(anchor) {
 export function comment(flags = 0) {
 	// we're not delegating to `template` here for performance reasons
 	if (hydrating) {
-		assign_nodes(
-			hydrate_start.previousSibling ?? hydrate_start,
-			hydrate_nodes[hydrate_nodes.length - 1]
-		);
+		assign_nodes(get_start(), hydrate_nodes[hydrate_nodes.length - 1]);
 
 		return hydrate_start;
 	}

packages/svelte/src/internal/client/reactivity/effects.js

@@ -305,7 +305,7 @@ export function template_effect(fn) {
  */
 export function block(anchor, flags, fn) {
 	const effect = create_effect(RENDER_EFFECT | BLOCK_EFFECT | flags, fn, true);
-	if (anchor !== null) effect.nodes = { start: null, end: anchor };
+	if (anchor !== null) effect.nodes = { start: null, anchor: null, end: anchor };
 	return effect;
 }
 

packages/svelte/src/internal/client/reactivity/types.d.ts

@@ -36,7 +36,11 @@ export interface Derived<V = unknown> extends Value<V>, Reaction {
 
 export interface Effect extends Reaction {
 	parent: Effect | null;
-	nodes: null | { start: undefined | null | TemplateNode; end: TemplateNode };
+	nodes: null | {
+		start: undefined | null | TemplateNode;
+		anchor: null | TemplateNode;
+		end: TemplateNode;
+	};
 	/** The associated component context */
 	ctx: null | ComponentContext;
 	/** The effect function */