I can confirm it does this on Win10 Firefox 67.0.3 as well

Can confirm it also happens on iOS 12.3.1 in Safari.

Confirmed on Pop_OS! 19.04 in Brave.

Same on MacOSX 10.14.5 on Firefox 67.0.3

Confirmed on Win10 Chrome 74.0.3729.169

Interesting! Confirmed on Win 10 / Chrome here as well.

I just tried listening to beforeprint event (see exampel below), but that wasn't triggered (as it is if calling window.print();). How can that dialog even be launched in a browser except usingwindow.print();?

window.addEventListener("beforeprint", function(event) { debugger; console.log("print", arguments); });

Confirming in Manjaro (testing branch), Firefox 67.0.3-0

+1

Just doing a bit of breakpointing, and the following line seems to trigger it from mono.js:

Above is prettified in Chrome having just traversed a bit of the stacktrace for the console errors that appear after the print dialog is dismissed.

Confirmed on macOS Mojave 10.14.5 Safari Version 12.1.1 (14607.2.6.1.1)

On iOS 12.3.1 in Safari, I get a message “This webpage has been blocked from automatically printing”, allowing it bring us the printer options for a one page print job.

Changing MidpointRounding.AwayFromZero to MidpointRounding.ToEven stops that behaviour.

My guess is that the error handler shown above by Pablissimo is calling window.print instead of it calling a method that prints the error to the console out.

so cool. would not be surprised if this is another amazing byproduct of name scoping in javascript when in browser.

A video reproduction of the bug :

Tested on macOS 10.14.5 Chrome 74.0.3729.169

Confirmed Firefox 67.0.3 on Archlinux 5.1.11-arch1-1-ARCH here as well. Truly cross platform

macOS 10.13.6, Safari 12.1.1

Just in case it's needed: Confirmed also on Windows 10 Home version 10.0.18362 with Opera 60.0.3255.170

I tried this on IE5.5 in a MacOS 9 VM and an Apple Laserwriter II spontaneously materialized on the floor

Confirmed on Chrome 72.0.3626.96 (Official Build) (64-bit) on Ubuntu 14.04

Confirmed on Linux - Ubuntu 19.04 running Firefox nightly 69.0a1 (2019-06-19) (64-bit)

Confirmed the print dialog opens on Linux - Ubuntu 18.04 LTS (64-bit) with Firefox 67.0.2 (64-bit)

Unable to trigger print dialog on Android - LineageOS 16 for Google Pixel, default Chrome/WebView browser

Confirmed in macOS 10.14.4 using Microsoft Edge Insider 77.0.189.3 (Official build) Dev (64-bit)

How it works?

Looks like some function somewhere calls print, meaning a local print function but this is probably set to window

confirmed on India Browser 2019

Confirmed in macOS 10.14.5 and Firefox 67.0.2 (64-bit)

Best Issue of 2019

Confirmed on Manjaro Linux - Chromium Version 75.0.3770.80 Arch Linux (64-bit)

Also the print dialog appears to require dismissing twice as well.

Confirmed on MacOS Mojave 10.14 with Firefox 67.0.3

Javascript is the best. If we had such architecture 20 years ago we would be doomed now.

Confirmed on Windows Vista 64-bit with Internet Explorer 9

Confirmed Win10 Chrome 74.0.3729.169

@PurHur

Javascript is the best. If we had such architecture 20 years ago we would be doomed now.

As shown in the thread earlier the browser is instructed to print. Is the computer doing A when instructed to do A an unusual thing outside the JavaScript world?

As shown in the thread earlier the browser is instructed to print. Is the computer doing A when instructed to do A an unusual thing outside the JavaScript world?

In good langues such things dont happen randomly if you dont pass a valid this object to your call because you made some magic.
Its not like the devs called window.print here. Its a side effect which should never happen.

to long to explain: Its bad that the language allows such sort of bugs.

confirmed: opens Print Butter dialogue on my Toaster

Confirmed: Ubuntu 18.04.2 LTS, Opera 60.0.3255.170

I don't think this bug needs to be confirmed anymore, except in cases where the bug is not present, such as in Tor Browser. Instead we should be discussing possible causes and solutions.

In good langues such things dont happen randomly if you dont pass a valid this object to your call because you made some magic.
Its not like the devs called window.print here. Its a side effect which should never happen.

to long to explain: Its bad that the language allows such sort of bugs.

So if someone were to override printf in a C program that would make C a bad language? Because you can do that. You probably shouldn't, but you can.

In good langues such things dont happen randomly if you dont pass a valid this object to your call because you made some magic.
Its not like the devs called window.print here. Its a side effect which should never happen.
to long to explain: Its bad that the language allows such sort of bugs.

So if someone were to override printf in a C program that would make C a bad language? Because you can do that. You probably shouldn't, but you can.

C is not Javascript and clean code in Asm doesnt exist.
Its the matter of it can happen accidentally not "im going to overwrite printf for the sake of a discussion".
How do you randomly overwrite printf in c?

In good langues such things dont happen randomly if you dont pass a valid this object to your call because you made some magic.
Its not like the devs called window.print here. Its a side effect which should never happen.
to long to explain: Its bad that the language allows such sort of bugs.

So if someone were to override printf in a C program that would make C a bad language? Because you can do that. You probably shouldn't, but you can.

Absolutely. There is an exhaustive list of valid criticisms of Javascript, but letting you run with scissors is not one of them.

Confirmed:

1.) Ubuntu 18.04.2 LTS, Mozilla FF 67.0.3 (64-Bit) & Google Chromium Version 75.0.3770.90
2.) Arch Linux x86_64 (Kernel 5.1.9-arch-1-ARCH) FF 67.0.3-1 & Chromium Version 75.3770.100

In good langues such things dont happen randomly if you dont pass a valid this object to your call because you made some magic.
Its not like the devs called window.print here. Its a side effect which should never happen.
to long to explain: Its bad that the language allows such sort of bugs.

So if someone were to override printf in a C program that would make C a bad language? Because you can do that. You probably shouldn't, but you can.

C is not Javascript and clean code in Asm doesnt exist.
Its the matter of it can happen accidentally not "im going to overwrite printf for the sake of a discussion".
How do you randomly overwrite printf in c?

Who said random? You can link a library with your own printf that tries to use the printer if you want, and if someone else hops on the project and doesn't know that...

This is human error. What you're suggesting is possible with pretty much any language.

It is prossible but you wont accidentally fall into it. Thats makes a bad language. But im out now. This is no rant forum.

def better_print(*args, **kwargs):
    import subprocess
    lpr =  subprocess.Popen("/usr/bin/lpr", stdin=subprocess.PIPE)
    lpr.stdin.write(' '.join(args))

import builtins
builtins.print = better_print

only that dotnet did not overwrite the print or round function at all. omg please

Instead it called the global print that - as the name suggests - prints what was given to it! What a shocker!

Best Issue of 2019

Best Issue of 2019 SO FAR
And just a typical day in JS development.

Changing MidpointRounding.AwayFromZero to MidpointRounding.ToEven stops that behaviour.

Yea, but that also switches from mercantile rounding to mathematical rounding.
Which is actually better, by the way, but unfortunately, results from .NET then don't match results from SQL-Server rounding - which means if you display results in report vs. forms yields a different result.
Also, it that value (rounded to 2 decimals) is multiplying another value (high), then the difference can be quite substantial.

Confirmed with Chromium on Funtoo (1.3-kit, baselayout 2.2.2 ## pure64):
Installed versions: 71.0.3578.30^d(06:56:13 AM 04/19/2019)(cups hangouts pic proprietary-codecs suid widevine -component-build -custom-cflags -gnome-keyring -jumbo-build -kerberos -neon -pulseaudio -selinux -system-ffmpeg -system-icu -system-libvpx -tcmalloc KERNEL="linux"

I like the idea of printing stack-traces on a real printer instead of console log

I like the idea of printing stack-traces on a real printer instead of console log

its a feature not a bug!

Confirmed with firefox 67.0.3 on Ubuntu 19.04

I like the idea of printing stack-traces on a real printer instead of console log

Yea, but on the off chance that this isn't meant sarcastically - please think of the environment before you needlessly print every single last crap.
Paper doesn't just come from the supplier, you know.

lol

this thread....

As amusing as the bug report is, and as funny as many of the responses here are, I'm locking down the issue while we work on it. Thanks for reporting it, @BillWagner!

We updated the version of blazor in try.dot.net and the issue is fixed now.