cmd/go: exclude $GOPATH/src/mod from “all” and “...” patterns in GOPATH mode

[bcmills]

After performing a go build in module mode, go build all in GOPATH mode emits a bunch of errors due to import path mismatches in $GOPATH/src/mod.

Since the code in $GOPATH/src/mod isn't intended to be buildable in GOPATH mode in the first place, we should explicitly ignore it.

~/src$ cd $GOPATH/src

~/src$ go get rsc.io/sampler

~/src$ pushd rsc.io/sampler
~/src/rsc.io/sampler ~/src

~/src/rsc.io/sampler$ GO111MODULE=on go build .
go: finding golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c
go: downloading golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c

~/src/rsc.io/sampler$ popd
~/src

~/src$ GO111MODULE=off go build all 2>&1 | grep mod/ | head -n 10
can't load package: package mod/golang.org/x/[email protected]: disallowed import path "mod/golang.org/x/[email protected]"
can't load package: package mod/golang.org/x/[email protected]/cases: disallowed import path "mod/golang.org/x/[email protected]/cases"
can't load package: package mod/golang.org/x/[email protected]/cmd/gotext: disallowed import path "mod/golang.org/x/[email protected]/cmd/gotext"
can't load package: package mod/golang.org/x/[email protected]/collate: disallowed import path "mod/golang.org/x/[email protected]/collate"
can't load package: package mod/golang.org/x/[email protected]/collate/build: disallowed import path "mod/golang.org/x/[email protected]/collate/build"
can't load package: package mod/golang.org/x/[email protected]/collate/tools/colcmp: disallowed import path "mod/golang.org/x/[email protected]/collate/tools/colcmp"
can't load package: package mod/golang.org/x/[email protected]/currency: disallowed import path "mod/golang.org/x/[email protected]/currency"
can't load package: package mod/golang.org/x/[email protected]/encoding: disallowed import path "mod/golang.org/x/[email protected]/encoding"
can't load package: package mod/golang.org/x/[email protected]/encoding/charmap: disallowed import path "mod/golang.org/x/[email protected]/encoding/charmap"
can't load package: package mod/golang.org/x/[email protected]/encoding/htmlindex: disallowed import path "mod/golang.org/x/[email protected]/encoding/htmlindex"

(CC: @rsc)

[rsc]

Yes, mod should just be invisible in GOPATH/src. That's in internal/search I think.

[rsc]

We could plausibly backport the GOPATH/src/mod exclusion to Go 1.9 and Go 1.10 as well.

[gopherbot]

Change https://golang.org/cl/125675 mentions this issue: cmd/go: exclude import paths beginning with mod/ from patterns

[anacrolix]

Any reason this stuff can't go in $GOPATH/mod or something other than $GOPATH/src? I posted to golang-dev just now on this.

[davecheney]

That would create a $HOME/mod directory for those who set $GOPATH=$HOME. As a counter proposal, why not make it $GOPATH/src/.mod then the usual exclusion rules apply.

…

On 25 July 2018 at 18:22, Matt Joiner ***@***.***> wrote: Any reason this stuff can't go in $GOPATH/mod or something other than $GOPATH/src? I posted to golang-dev just now on this. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#26401 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAcA1ikp9Lxen1AA5pnVWR65JKRxM3Wks5uKCq7gaJpZM4VRc52> .

[anacrolix]

How do those people setting $GOPATH=$HOME rationalize pkg? .mod seems good if the existing tools work with that.

[bcmills]

How do those people setting $GOPATH=$HOME rationalize pkg?

I mostly close my eyes and pretend it isn't there. (And soon it won't be! See #4719.)

[anacrolix]

Regarding the CL: It would be nice if "mod" was a constant somewhere. Similarly for its use elsewhere in the code base.

[bcmills]

On hold pending a decision on whether to move the module cache someplace where it would be ignored by default (outside of $GOPATH/src or in a subdirectory beginning with . or _).

[gopherbot]

Change https://golang.org/cl/126755 mentions this issue: cmd/go: move module cache from $GOPATH/src/mod to $GOPATH/pkg/mod