From a2ac1d91fa6cfb93b19475976742a1daacf8f4eb Mon Sep 17 00:00:00 2001
From: Cris Ward <cris@duodesign.co.uk>
Date: Sun, 2 Feb 2020 21:31:18 +0000
Subject: [PATCH] disconnecting mutation observer on disconnect

---
 src/compiler/compile/render_dom/index.ts | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/compiler/compile/render_dom/index.ts b/src/compiler/compile/render_dom/index.ts
index 1dcffff056..55691aecf6 100644
--- a/src/compiler/compile/render_dom/index.ts
+++ b/src/compiler/compile/render_dom/index.ts
@@ -446,8 +446,8 @@ export default function dom(
 						this._root =this.attachShadow({ mode: '${options.shadowDom}' });
 					` || b`
 						this._copycontent();
-						const observer = new MutationObserver(() => this._slotcontent());
-						observer.observe(this, {childList: true, subtree: true});
+						this.slotObserver = new MutationObserver(() => this._slotcontent());
+						this.slotObserver.observe(this, {childList: true, subtree: true});
 					`}
 					${css.code && !lightDom && b`this._root.innerHTML = \`<style>${css.code.replace(/\\/g, '\\\\')}${options.dev ? `\n/*# sourceMappingURL=${css.map.toUrl()} */` : ''}</style>\`;`}
 					${should_add_css && lightDom && b`if (!@_document.getElementById("${component.stylesheet.id}-style")) ${add_css}();`}
@@ -544,6 +544,17 @@ export default function dom(
 					}
 				}` as FunctionExpression
 			});
+
+			declaration.body.body.push({
+				type: 'MethodDefinition',
+				kind: 'method',
+				static: false,
+				computed: false,
+				key: { type: 'Identifier', name: 'disconnectedCallback' },
+				value: x`function() {
+					this.slotObserver.disconnect();
+				}` as FunctionExpression
+			});
 		}
 
 		declaration.body.body.push(...accessors);