We use reflex to restart our local app whenever we make changes to any Go file. But I run into a small problem, because we use Go mod with the vendor pattern, reflex ends up on our go.mod and go.sum files, but I really don’t want them there. They are not part of the app and should not be vendored.
I didn’t want to ask developers to run go mod tidy before sending a Pull Request, so I looked into using a git pre-commit hook. After some trial and error, I ended up with:
#!/bin/bash
# format go code before commit
# exclude vendor folder and go installation (affects CI/CD)
gofmt -w -e `find . -name "*.go" -not -path "./go/*" | grep -v vendor`
# remove any extra dependency we don't need
go mod tidy
This file was committed to our repo, at the path githooks/pre-commit.
Side note.
You need to ask each dev to run git config core.hooksPath ./githooks to activate the hook path. This is a local by default command, it will only affect this repository.
Problems.
The hook seemed to had worked, but here and there I would run into a corner case where a PR would still make it with the extra entries in go.mod. Today, I had a few minutes to look into it and it turns out that a pre commit hook doesn’t update the changes you had already added (staged changes). In other words, the pre commit hook run, it cleaned up go.mod, but it did not run git add on the changed files. You had to stage the new changes to make them part of your Pull Request.
So what do we do now?
A small change:
#!/bin/bash
# format go code before commit
# exclude vendor folder and go installation (affects CI/CD)
gofmt -w -e `find . -name "*.go" -not -path "./go/*" | grep -v vendor`
# remove any extra dependency we don't need
go mod tidy
git diff --exit-code
Adding git diff --exit-code as the last line causes the pre-commit hook to cancel the commit call, then the dev simply reruns whichever commit command they had run, and now the code will be as I had expected it, clean.
Thank you for reading and don’t hesitate to leave a comment/question.
Diego