chore: tweak Map/Set for better inspect output (#12013)

* chore: tweak Map/Set for better inspect output

* chore: tweak Map/Set for better inspect output

* chore: tweak Map/Set for better inspect output

* chore: tweak Map/Set for better inspect output

* chore: tweak Map/Set for better inspect output

* changeset

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

.changeset/eleven-hounds-pump.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+chore: clear `Map`/`Set` before triggering `$inspect` callbacks

packages/svelte/src/reactivity/map.js

@@ -122,9 +122,12 @@ export class ReactiveMap extends Map {
 	}
 
 	clear() {
+		if (super.size === 0) {
+			return;
+		}
+		// Clear first, so we get nice console.log outputs with $inspect
+		super.clear();
 		var sources = this.#sources;
-
-		if (super.size !== 0) {
 		set(this.#size, 0);
 		for (var s of sources.values()) {
 			set(s, -1);
@@ -132,8 +135,6 @@ export class ReactiveMap extends Map {
 		increment(this.#version);
 		sources.clear();
 	}
-		super.clear();
-	}
 
 	#read_all() {
 		get(this.#version);

packages/svelte/src/reactivity/set.js

@@ -117,7 +117,11 @@ export class ReactiveSet extends Set {
 	}
 
 	clear() {
-		if (super.size !== 0) {
+		if (super.size === 0) {
+			return;
+		}
+		// Clear first, so we get nice console.log outputs with $inspect
+		super.clear();
 		var sources = this.#sources;
 
 		for (var s of sources.values()) {
@@ -129,9 +133,6 @@ export class ReactiveSet extends Set {
 		increment(this.#version);
 	}
 
-		super.clear();
-	}
-
 	keys() {
 		return this.values();
 	}