cmd/go: list reports packages as stale immediately after their "go get"

[siebenmann]

What version of Go are you using (go version)?

go version devel +c52e27e68d Sun Feb 11 20:41:48 2018 +0000 linux/amd64

Does this issue reproduce with the latest release?

This doesn't happen on Go 1.9.4.

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOOS="linux"

What did you do?

Here is a simple reproduction, showing a just fetched and built command package being reported as stale due to a stale dependency.

$ export GOPATH=/tmp/gp
$ mkdir $GOPATH
$ go get mvdan.cc/sh/cmd/shfmt
$ go list -f '{{.ImportPath}} - {{.Stale}} - {{.StaleReason}}' mvdan.cc/sh/cmd/shfmt
mvdan.cc/sh/cmd/shfmt - true - stale dependency: mvdan.cc/sh/fileutil

This appears to happen for anything that has dependencies outside of the core packages, including dependencies to golang.org/x packages.

[mvdan]

Seems related to whether or not go install was called on the dependencies directly:

$ go install -v mvdan.cc/sh/cmd/shfmt
$ go list -f '{{.ImportPath}} - {{.Stale}} - {{.StaleReason}}' mvdan.cc/sh/cmd/shfmt
mvdan.cc/sh/cmd/shfmt - true - stale dependency: mvdan.cc/sh/fileutil
$ go install -v mvdan.cc/sh/fileutil
$ go list -f '{{.ImportPath}} - {{.Stale}} - {{.StaleReason}}' mvdan.cc/sh/cmd/shfmt
mvdan.cc/sh/cmd/shfmt - false -

[mvdan]

go build -v mvdan.cc/sh/fileutil does not seem to fix it, though.

[mvdan]

Seems like the .a file for the library isn't being written to by go install when called on the package that imports the library. But, if go install is called directly on the library, it does write the .a file.

useCache on the library package also returns different results on both of these cases - it's returns true only when go install was called on the library directly.

I've tried debugging this further and possible fixes, but I'm not sure how this is supposed to behave. @rsc, thoughts?

[bradfitz]

I'll actually promote this to Go 1.10 because it involves the new build cache (potentially). I'll let Russ decide whether it's important for 1.10.

[bradfitz]

We decided in the release meeting to think about this for Go 1.10.1.