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0 pointsnbadg5mo ago0 comments

If you only want your own code to see the patch, then why not just wrap it?

I mean if you really need super strong isolation, you can always create a copy of the library object; metaprogramming, dynamic classes, etc, all make it really easy to even, say, create a duplicate class object with references to the original method implementations. Or decorated ones. Or countless other approaches.

My point isn't that I don't see problems that could be solved by this; my point is that I can't think of any problems that this solves, that wouldn't be better solved by things that don't do any innards-fiddling in what is arguably the most sharply-edged part of python: packaging and imports.

And speaking from experience... if you think patching can fail in subtle edge cases, then I've got some bad news for you re: import hooks.

At the end of the day, people who might use this library are looking for a solution to a particular problem. When documenting things, it's really important to be explicit about the pros and cons of your solution, from the perspective of someone with a particular problem, and not from the perspective of someone who's built a particular solution. If I need to drive a nail, and you're selling wrenches, I don't want to hear about all of the features of your wrenches; I want to know if your wrench can drive my nail, and why I would ever want to choose it instead of a hammer.

I can think of a lot of differently-shaped metaphorical nails that fall under the broad umbrella of "I need to change some upstream code but don't want to maintain a fork". And I can think of a whole lot of python-specific specialty hammers that can accomplish that task. But I still can't think of a signle situation where using import hooks to solve the problem is doing anything other than throwing a wrench into a very delicate gearbox. That is the explanation I would need, if I were in the market for such a solution, to evaluate modshim as a potential approach.

0 comments

Izkata5mo ago

> I mean if you really need super strong isolation, you can always create a copy of the library object; metaprogramming, dynamic classes, etc, all make it really easy to even, say, create a duplicate class object with references to the original method implementations. Or decorated ones. Or countless other approaches.

> My point isn't that I don't see problems that could be solved by this; my point is that I can't think of any problems that this solves, that wouldn't be better solved by things that don't do any innards-fiddling in what is arguably the most sharply-edged part of python: packaging and imports.

All these examples have the dependency order wrong, and you're right on those - it's simpler to wrap them somehow. But this is doing something different, that is either much harder or outright impossible with those methods: Tweaking something internal to the module while leaving its interface alone. This is shown in both their examples where they modify the TextWrapper object but then use it through the library's wrap() function, and modify the Session object but then just use the standard get() interface to requests.

nbadgOP5mo ago

In that case I'd opt for dynamic module creation using metaprogramming instead of an import hook. And I personally would argue that grabbing the code objects from module members and re-execing them into a new module object to re-bind their globals is simpler than an AST transformation.

But regardless of the transformation methodology: the import hook itself is just a delivery mechanism for the modified code. There's nothing stopping the library from using the same transformation mechanism but accessing it with dynamic programming techniques instead of an import hook. And there's nothing you can't do that way.

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