No way to catch exceptions in reactive statements

[BartVanBeurden]

Describe the bug

When a reactive statement throws an error, there is no mechanism to catch it.

1. You cannot try/catch the reactive statement ($: has no effect outside of the top-level)
2. window.onerror does not catch it
3. window.onunhandledrejection does not catch it

The best you can do is try/catch inside a function that is reactively called, but my goal is to have a global exception handler to handle all exceptions that I did not expect...

Reproduction

https://svelte.dev/repl/d3a8223398e5414a9b19d63bf1b46a34?version=3.44.1

Logs

No response

System Info

System:
    OS: Windows 10 10.0.19042
    CPU: (16) x64 AMD Ryzen 7 5800X 8-Core Processor
    Memory: 30.93 GB / 63.90 GB
  Binaries:
    Node: 16.3.0 - C:\Program Files\nodejs\node.EXE
    npm: 7.22.0 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Spartan (44.19041.1266.0), Chromium (95.0.1020.53)     
  npmPackages:
    rollup: ^2.56.3 => 2.59.0
    svelte: ^3.42.4 => 3.44.1

Severity

annoyance

[Prinzhorn]

Related

#1096
sveltejs/rfcs#46

[dummdidumm]

Closing as duplicate of the issues mentioned by @Prinzhorn

[Crisfole]

I don't think this is a duplicate, I think it's a misunderstanding. I know this was a long time ago, but @dummdidumm and @BartVanBeurden you can use a try/catch as a reactive statement:

<script>
	let value = 'world';
	
	function test(input) {
		if (Math.random() < .5) {
			console.log("Throwing");
			throw new Error("Oops");
		}
		console.log("Didn't throw");
		return input;
	}
	
	let tested = value;
	$: try {
		tested = test(value);
	} catch (err) {
		console.log("Caught", err);
		tested = err.message;
		console.log(tested);
	}
</script>

<input type=text bind:value />

<h1>Hello {tested}!</h1>