submodules make another repo’s URL part of a repo. Thus, they couple source code with code and build hosting infrastructure, which is not good. For example it is not possible to clone a repo and its submodules to different host whithout forking the repo.
submodules are used for library-like modules of a codrme base. But they promote much stronger coupling than a proper backwards-compatible library API which is bad.
submodules are used to vendor libraries which is bad and in the end only cover up problems in build and packaging systems. Using the distributions package manager or a clean, powrful system like Guix would be better. Language-specific package managers are not as good a solution but still better than vendoring.
You have to tediously git submodule update --init--recursive every time you checkout a commit. There’s an option to do it automatically but it’s super buggy and will break your .git directory.
Switching between branches that have different sets of submodules doesn’t really work. Git won’t remove/recreate the submodules like it will for normal directories. Worst case is changing a directory to a submodule or vice versa.
If you’re working on a feature that spans several submodules you have to switch branches in all of them instead of once.
Making co-dependant changes across submodules is a nightmare.
If you’re using submodules for first party code (not uncommon), it basically creates a new public interface where you didn’t have one before. Now you have to worry about backwards compatibility and testing becomes much harder. Monorepos don’t have that problem.
The list goes on… Some of them depend on exactly what you’re using them for.
The slightly frustrating thing is that there isn’t a great answer for what to use instead. Git subtree has its own problems. Language-specific package managers do too. There aren’t any good languages agnostic package managers I know of.
I’m really hoping Jujutsu will come up with a better solution because it is possible. But it’s hard, and they are constrained by Git compatibility so I won’t hold my breath.
Which didadvantages of submodules did you find?
I see tree:
git submodule update --init --recursiveevery time you checkout a commit. There’s an option to do it automatically but it’s super buggy and will break your.gitdirectory.The list goes on… Some of them depend on exactly what you’re using them for.
The slightly frustrating thing is that there isn’t a great answer for what to use instead. Git subtree has its own problems. Language-specific package managers do too. There aren’t any good languages agnostic package managers I know of.
I’m really hoping Jujutsu will come up with a better solution because it is possible. But it’s hard, and they are constrained by Git compatibility so I won’t hold my breath.
Packaging libraries with Guix is a great solution.
Also, strict backwards compatibility in APIs is totally worth it. It makes developing larger systems so much easier.