Ytdyklly

Im currently working on a bigger project which unfortunately has some files where software quality guidelines where not always followed. This includes big files (read 2000-4000 lines) which clearly contain multiple distinct functionalities.

Now I want to refactor these big files into multiple small ones. The issue is, since they are so big, multiple people (me included) on different branches are working on these files. So I cant really branch from develop and refactor, since merging these refactorings with other peoples changes will become difficult.

We could of course require everyone to merge back to develop, "freeze" the files (ie. dont allow anyone to edit them anymore), refactor, and then "unfreeze". But this is not really good either, since this would require everyone to basically stop their work on these files until refactoring is done.

So is there a way to refactor, dont require anyone else to stop working (for to long) or merge back their feature branches to develop?

You have correctly understood that this is not so much a technical as a social problem: if you want to avoid excessive merge conflicts, the team needs to collaborate in a way that avoids these conflicts.

This is part of a general problem with Git, in that branching is very easy but merging can still take a lot of effort. Development teams tend to launch a lot of branches and are then surprised that merging them is difficult, possibly because they are trying to emulate the Git Flow without understanding its context.

The general rule to fast and easy merges is to prevent big differences from accumulating, in particular that feature branches should be very short lived (hours or days, not months). A development team that is able to rapidly integrate their changes will see fewer merge conflicts. If some code isn't yet production ready, it might be possible to integrate it but deactivate it through a feature flag. As soon as the code has been integrated into your master branch, it becomes accessible to the kind of refactoring you are trying to do.

That might be too much for your immediate problem. But it may be feasible to ask colleagues to merge their changes that impact this file until the end of the week so that you can perform the refactoring. If they wait longer, they'll have to deal with the merge conflicts themselves. That's not impossible, it's just avoidable work.

You may also want to prevent large swaths of dependent code by making API-compatible changes. For example, if you want to extract some functionality into a separate module:

1. Extract the functionality into a separate module.


2. Change the old functions to forward their calls to the new API.


3. Over time, port dependent code to the new API.


4. Finally, you can delete the old functions.

This multi-step process can avoid many merge conflicts. In particular, there will only be conflicts if someone else is also changing the functionality you extracted. The cost of this approach is that it's much slower than changing everything at once, and that you temporarily have two duplicate APIs. This isn't so bad until something urgent interrupts this refactoring, the duplication is forgotten or deprioritized, and you end up with a bunch of tech debt.

But in the end, any solution will require you to coordinate with your team.

Do the refactoring in smaller steps. Lets say your large file has the name Foo:

1. Add a new empty file Bar - commit it to "trunk".




2. Find a small portion of the code in Foo which can be moved over to Bar. Apply the move, update from trunk, build and test the code, and commit to "trunk".




3. Repeat step 2 until Foo and Bar have equal size (or whatever size you prefer)

That way, next time your team mates update their branches from trunk, they get your changes in "small portions" and can merge them one-by-one, which is a lot easier than having to merge a full split in one step. Same holds when in step 2 you get a merge conflict because someone else in between updated trunk.

This won't eliminate merge conflicts, but it restricts each conflict to a small area of code, which is way more manageable.

And of course - communicate the refactoring in the team. Inform your mates what you are doing, so they know why they have to expect merge conflicts for the particular file.

You are thinking of splitting the file as an atomic operation, but there are intermediate changes you can make. The file gradually became huge over time, it can gradually become small over time.

Pick a part that hasn't had to change in a long time (git blame can help with this), and split that off first. Get that change merged into everyone's branches, then pick the next easiest part to split. Maybe even splitting one part is too big a step and you should just do some rearranging within the large file first.

If people aren't frequently merging back to develop, you should encourage that, then after they merge, take that opportunity to split off the parts they just changed. Or ask them to do the splitting off as part of the pull request review.

The idea is to slowly move toward your goal. It will feel like progress is slow, but then suddenly you'll realize your code is a lot better. It takes a long time to turn an ocean liner.

Fixing this problem requires buy-in from the other teams because you're trying to change a shared resource (the code itself). That being said, I think there's a way to "migrate away" from having huge monolithic files without disrupting people.

I would also recommend not targeting all the huge files at once unless the number of huge files is growing uncontrollably in addition to the sizes of individual files.

Refactoring large files like this frequently causes unexpected problems. The first step is to stop the big files from accumulating additional functionality beyond what's currently in master or in development branches.

I think the best way to do this is with commit hooks that block certain additions to the large files by default, but can be overruled with a magical comment in the commit message, like @bigfileok or something. It's important to be able to overrule the policy in a way that's painless but trackable. Ideally, you should be able to run the commit hook locally and it should tell you how to override this particular error in the error message itself.

The commit hook could check for new classes or do other static analysis (ad hoc or not). You can also just pick a line or character count that's 10% larger than the file currently is and say that the large file can't grow beyond the new limit. You can also reject individual commits that grow the new file by too many lines or too many characters or w/e.

Once the large file stops accumulating new functionality, you can refactor things out of it one at a time (and reduce the tresholds enforced by the commit hooks at the same time to prevent it from growing again).

Eventually, the large files will be small enough that the commit hooks can be completely removed.

Wait until hometime. Split the file, commit and merge to master.

Other people will have to pull the changes into their feature branches in the morning like any other change.