[JoshTriplett]

    $ python3
    Python 3.13.7 (main, Aug 20 2025, 22:17:40) [GCC 14.3.0] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    >>> class MagicRedirect:
    ...     def __setattr__(self, name, value):
    ...         if name == "href":
    ...             print(f"Redirecting to {value}")
    ...             exit()
    ... 
    >>> location = MagicRedirect()
    >>> location.href = "https://example.org/"
    Redirecting to https://example.org/
    $

[dvt]

You're overloading a setter here. It's cute, I did it in JS as well, but I don't really think it's a counterexample. It would be odd to consider this the norm (per the thought process of the original blog post).

[rowanG077]

This is not some weird thing. Here is a run of the mill example where python can have properties settting do anything at all. And it's designed like that.

    import sys
    
    class Foo:
        @property
        def bar(self):
            return 10
            
        @bar.setter
        def bar(self, value):
            print("bye")
            sys.exit()
    
    foo = Foo()
    foo.bar = 10

Or in C# if you disqualify dynamic languages:

    using System;

    class Foo
    {
        public int Bar
        {
            get { return 10; }
            set
            {
                Console.WriteLine("bye.");
                Environment.Exit(0);
            }
        }
    }

    class Program
    {
        static void Main()
        {
            Foo obj = new Foo();
            obj.Bar = 10;
        }
    }

This is not some esoteric thing in a lot of programming languages.

[dvt]

You're also overriding a setter. Maybe I'm going against the grain here, but it's absolutely esoteric. The assignment operator is not supposed to have side-effects, and maybe this is the logician in me, but the implication that we should be aware that weird stuff might be happening when we do `x = 5` is fundamentally bonkers.

[JoshTriplett]

You started with "In no language has a variable assignment ever stopped execution", and now you're saying "The assignment operator is not supposed to have side-effects". location.href is a counterexample, and there are many counterexamples throughout various tools and languages and libraries. Deciding how you think things should work does not affect how things do work, and it's important to understand the latter. (I do agree it's bad practice, but it happens and people do not always fully control the environments they must work with.)

And given that location.href does have a side effect, it's not unreasonable for someone to have assumed that that side effect was immediate rather than asynchronous.

That said, if you don't like working with such languages, that's all the more reason to select languages where that doesn't happen, which comes back to the point made in the article.

[dvt]

> You started with "In no language has a variable assignment ever stopped execution",

The irony is that I'm still technically correct, as literally every example (from C++, to C#, to Python, to JS) have been object property assignments abusing getters and setters—decidedly not variable assignments (except for the UB example).

[rowanG077]

The entire discussion is about a property assignment. Which in colloquial usage is also called variable assignment. Which is obvious since nobody corrected you on that. You now trying to do a switcheroo is honestly ridiculous.

[kketch]

Technically no. Producing side effects from a setter is not unexpected, even if it often the best idea to have a setter have a lot of unexpected side effects. However producing side effects from getters is definitely unexpected and should not be done. Interestingly it's one of the areas where rust is really useful, it forces you express your intent in terms of mutability and is able to enforce these expectations we have.

[jibal]

Assignment is by definition a side effect.

This whole discussion is completely off kilter by all parties because setting the variable doesn't terminate the script--that's the bug; it simply sets the variable (that is, it sets a property in a globally accessible structure). Rather, some time later the new page is loaded from the variable that was set.

Aside from that, your comments are riddled with goalpost moving and other unpleasant fallacies and logic errors.

FWIW I grew up in the days (well, actually I was already an adult who had been programming for a decade) when storing values in the I/O page of PDP-11 memory directly changed the hardware devices that mapped their operation registers to those memory addresses. That was the main reason for the C `volatile` keyword.

[toast0]

> The assignment operator is not supposed to have side-effects,

Memory mapped I/O disagrees with this. Writing a value can trigger all sorts of things.

[kketch]

assignments are side effects, even more so when they are done through a setter on an object / class instance

[dminik]

But window.location.href is already an overloaded setter. It schedules a page navigation.