Comment by lolinder
3 years ago
I would be horrified if this grew much further. It's perfectly fine for its current scope, but the architecture would not scale at all to a full interpreter without essentially starting from scratch.
3 years ago
I would be horrified if this grew much further. It's perfectly fine for its current scope, but the architecture would not scale at all to a full interpreter without essentially starting from scratch.
Yeah, at some point you have to question if it's worth spending time maintaining a quirky, error-prone, ever-growing mini-JS interpreter, or just adding a dependency on v8 or node or something. And then you don't have to worry about supporting new scripts, as they'll just always work.
If you were going to use a C library, the most logical is QuickJS since it has Python bindings, is small, perfectly fast enough for the kind of needs yt-dl has, and it has excellent coverage of the standard and passes conformance tests.
That said I think a decent Python-native JS interpreter isn't that bad of an idea, it definitely needs a separate project and a more sophisticated architecture but it's an attainable goal.
Being pure Python has an advantage where it can be run e.g., in Pythonista 3 for iOS (which allows to implement various functions such as: download just audio, send link to be viewed on a separate device).
How much does it need to "scale"? It just has to be fast and correct enough for the a CLI to work.
"Scale" has multiple meanings, and here I'm not talking about speed.
This interpreter is built around matching specific Regex patterns and then immediately executing hard-coded behaviors with a few slots for parameters. It's missing a whole lot of the skeletal structure that would be necessary to "scale" it up to support a generally useful subset of JS, much less the entire language. Without the necessary structure, it would be a buggy mess that's impossible to maintain, and you can't just take the existing code and structure it better: it's built on the wrong foundation. That's what I mean when I say it won't scale.
That's not a judgement against the team that wrote it! It meets their needs fine, and choosing a minimal solution is great engineering that takes a lot of guts in the current software culture. I like what they've done here. Just don't take it and try to scale it up into a full JS runtime.