proposal: cmd/go: build argument to disable readonly $GOPATH/pkg/mod

[Psykar]

What did you do?

This has been discussed previously:
#27161

Most build systems (buildroot et al.) expect to be able to do an rm -rf to do a completely fresh build. However, because the pkg sets it's containing directories to read only, this command will fail.

Requiring a custom command to be added to various Makefile's scattered around the place to clean this up is far from ideal.

A potential solution might be to add an environment variable to disable this read only permission change on the pkg directory.
Open to other alternatives - but ideally there needs to be a command on the BUILD side that allows rm -rf to work correctly.

[agnivade]

#27161 clearly mentions that it is intentional and will remain this way.

It would be good if your proposal addresses the issue raised by @rsc here.

[Psykar]

@agnivade - the default being read only makes complete sense to me, I'm not suggesting changing that.
I would have thought a manual flag to allow the directories to be writeable would be acceptable - to tell golang that I know what I'm doing, it's OK to not lock the directory down?

It's worth noting in this kind of scenario (embedded build systems), tests are not going to be run as part of the build process, and the whole build directory (which includes this cache directory) frequently gets removed entirely.

So we're looking for a way to allow rm -rf to work on the $GOPATH/pkg/mod directory while still blocking tests from being able to write files to this directory? The two seem mutually exclusive to me unfortunately, hence suggesting the manual flag.

(As an aside, happy to do the PR for this if it's acceptable)

[agnivade]

Marking it as a proposal.

[bcmills]

You can already run chmod u+w -R $GOPATH/pkg/mod or go clean -modcache explicitly before cleaning up.

Why would an explicit argument be more helpful than an explicit command? Seems like you have to update your configuration either way.

[pbrkr]

@bcmills: The problem for us is that we can't modify our CI system to run those commands at the start of a build. The fault here is 100% with the golang compiler, it has no valid case for removing the write bit from files & directories in the build tree.

Running git clean -xffd (which the CI system does) should be sufficient to fully clean up a build directory.