Large parts of the rewrite came from contributors who had never worked on fish before.
That’s pretty useful alone.
And there’s this:
Thread Safety
Allowing background functions and concurrent functions has been a goal for many years. I have been nursing a long-lived branch which allows full threaded execution. But though the changes are small, I have been reluctant to propose them, because they will make reasoning about the shell internals too complex: it is difficult in C++ to check and enforce what crosses thread boundaries.
This is Rust’s bread and butter: we will encode thread requirements into our types, making it explicit and compiler-checked, via Send and Sync. Rust will allow turning on concurrent mode in a safe way, with a manageable increase in complexity, finally enabling this feature.
Vibes are just as important to free/open source software as proprietary software and although there were solid technical reasons for the port, the PR outcomes are added benefits.
Seems one of the main reasons is to use Rust’s thread safety to enable “concurrent mode”. Anyone with the knowledge able to explain what advantages that would yield for an end fish user?
will have to wait for the first while loop to complete, which takes 0.5s, and then run the second.
So it takes 0.5s until you get the first output and a full second until you get all of it.
Making this concurrent means you get the first line immediately and all of it in 0.5s.
While this is an egregious example, it makes all builtin | builtin pipelines slower.
Other shells solve this via subshells - they fork off a process for the middle part of the pipeline at least. That has some downsides in that it’s annoyingly leaky - you can’t set variables or create a background job in those sections and then wait for them outside, because it’s a new process and so the outer shell never sees them.
While I agree, most people shouldn’t have to be concerned with it, you can’t deny the resource impacts of various languages, libraries and frameworks, like compare the memory usage of Discord or Teams with those of FOSS chat applications, and you’ll notice those two consistently eating much more memory. You can also compare compute speeds of a higher level language like Python vs lower level languages like Rust and you’ll find that Rust is quite a bit faster (though generally takes more dev time). So yes, users shouldn’t have to be concerned with involved languages, but if you’re running something on a low-resource device, such as a Raspberry Pi, those little details can make all the difference.
PL can have a large impact on features, bugs, bug reports, troubleshooting, performance and documentation. Particularly when dev resources are limited.
It’s hard to see how this opinion holds any water.
Rust is a great choice for a shell built as an interactive shell that doesn’t have to be core to the OS. Over C++ this also makes development more accessible to young programmers.
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