cmd/go: make it easier for toolexec authors to get access to full package path

[josharian]

I'm writing a toolexec-able program for which I want to know the full package path for whatever code is being operated on. The code to figure out this package path is currently a pile of hacks. E.g. for compile, look for the -p arg. For asm, use -trimpath to figure out $WORK and then slice that off the -o arg. This breaks down entirely for invocations of cgo with -dynpackage.

I would like to have cmd/go pass extra information when toolexec is in use. For backwards compatibility, I propose to do this via an environment variable, something like TOOLEXEC_PKG_PATH (improvements welcome). There might be other, similar bits of data to add in the future.

Feedback and suggestions requested. I'm going to hack this in myself anyway, it's just a question of whether I should plan to mail a CL at the end (for 1.8, of course).

[bradfitz]

I had this same pain recently but figured I was just doing something wrong. Glad I'm not alone.

[rsc]

OK. Let's do TOOLEXEC_IMPORTPATH for now.

[mvdan]

@josharian given that you self-assigned this, do you still intend to implement this? If not, I'd like to have a go for 1.16 :)

[josharian]

All yours.

[gopherbot]

Change https://golang.org/cl/263357 mentions this issue: cmd/go: set TOOLEXEC_IMPORTPATH for -toolexec tools