From 758b3ae0b0711dac8b9d4f709ab42e4dc3d69de2 Mon Sep 17 00:00:00 2001
From: Emiliano <emiliano.bovetti@gmail.com>
Date: Tue, 27 Mar 2018 18:30:30 +0200
Subject: [PATCH] fixes elm/core#952

Checking callback type on port subscribe

Currently calling `elm.ports[portName].subscribe(undefined)` will cause an exception only when subscribers get called, this commit adds a type check before pushing the callback on subscription list
---
 src/Elm/Kernel/Platform.js | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/Elm/Kernel/Platform.js b/src/Elm/Kernel/Platform.js
index d3cf8db0..d897ac5f 100644
--- a/src/Elm/Kernel/Platform.js
+++ b/src/Elm/Kernel/Platform.js
@@ -389,6 +389,11 @@ function _Platform_setupOutgoingPort(name)
 
 	function subscribe(callback)
 	{
+		if (typeof callback !== 'function')
+		{
+			throw new Error('Trying to subscribe an invalid callback on port `' + name + '`');
+		}
+
 		subs.push(callback);
 	}