Dependency solving is a hard (NP-complete) problem in all non-trivial component models due to either mutually incompatible versions of the same packages or explicitly declared package conflicts. As such, software upgrade planning needs to rely on highly specialized dependency solvers, lest falling into pitfalls such as incompleteness-a combination of package versions that satisfy dependency constraints does exist, but the package manager is unable to find it. In this paper we look back at proposals from dependency solving research dating back a few years. Specifically, we review the idea of treating dependency solving as a separate concern in package manager implementations, relying on generic dependency solvers based on tried and tested techniques such as SAT solving, PBO, MILP, etc. By conducting a census of dependency solving capabilities in state-of-the-art package managers we conclude that some proposals are starting to take off (e.g., SAT-based dependency solving) while-with few exceptions-others have not (e.g., out-sourcing dependency solving to reusable components). We reflect on why that has been the case and look at novel challenges for dependency solving that have emerged since.

中文翻译：

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依赖解决仍然很难，但我们正在变得更好

由于相同包的相互不兼容版本或显式声明的包冲突，依赖解决是所有非平凡组件模型中的一个困难（NP 完全）问题。因此，软件升​​级规划需要依赖高度专业化的依赖求解器，以免陷入不完整等陷阱——满足依赖约束的包版本组合确实存在，但包管理器无法找到它。在本文中，我们回顾了几年前的依赖解决研究的建议。具体来说，我们回顾了将依赖解决作为包管理器实现中的一个单独关注点的想法，依赖于基于久经考验的技术（如 SAT 解决、PBO、MILP 等）的通用依赖解决方案。通过对最先进的包管理器中的依赖解决能力进行普查，我们得出结论，一些提议开始起飞（例如，基于 SAT 的依赖解决），而除了少数例外 - 其他人还没有（例如，退出-source 对可重用组件的依赖解决）。我们反思为什么会出现这种情况，并研究此后出现的依赖解决的新挑战。