cmd/go: errors emitted multiple times for packages with missing checksums

[bcmills]

$ go mod edit -go=1.17

$ go list all
m.go:3:8: missing go.sum entry for module providing package golang.org/x/tools/go/packages (imported by example.com); to add:
        go get example.com

$ go mod edit -go=1.16

$ go list all
go: golang.org/x/tools@v0.1.1: missing go.sum entry; to add it:
        go mod download golang.org/x/tools
go: golang.org/x/tools@v0.1.1: missing go.sum entry; to add it:
        go mod download golang.org/x/tools

$ go1.16.4 list all
go: golang.org/x/tools@v0.1.1: missing go.sum entry; to add it:
        go mod download golang.org/x/tools

-- go.mod --
module example.com

go 1.17

require golang.org/x/tools v0.1.1
-- m.go --
package example

import _ "golang.org/x/tools/go/packages"

This is a regression introduced in Go 1.17, probably by one of my changes for #36460.

CC @jayconrod @matloob

[bcmills]

(Found while writing a regression test for #46141.)

[gopherbot]

Change https://golang.org/cl/320172 mentions this issue: cmd/go: add tests illustrating what happens when Go 1.16 is used in a Go 1.17 main module

[bcmills]

(Unmarking as release-blocker. Realistically, nobody is going to be confused by a duplicated message, and if this were the last bug remaining in the release we wouldn't want to hold it up.)

[ianlancetaylor]

@bcmills This is in the 1.18 milestone; time to move to 1.19? Thanks.

[ianlancetaylor]

@bcmills @matloob This issue is marked for 1.19. It's just been rolling forward in milestones. Should it move to Backlog?

[jeanbza]

I'm unable to reproduce this FWIW:

$ go version
go version go1.19
$ cat go.mod
module github.com/example/example

go 1.17

require golang.org/x/tools v0.1.12 // indirect
deklerk at legate in ~/workspace/mult_errors
$ cat go.sum
deklerk at legate in ~/workspace/mult_errors
$ go list -m all
go: golang.org/x/tools@v0.1.12: missing go.sum entry; to add it:
	go mod download golang.org/x/tools
deklerk at legate in ~/workspace/mult_errors
$ go mod edit -go=1.16
deklerk at legate in ~/workspace/mult_errors
$ go list -m all
go: golang.org/x/tools@v0.1.12: missing go.sum entry; to add it:
	go mod download golang.org/x/tools

[bcmills]

@jadekler, try go list all without setting -m?

[jeanbza]

Aha, yes, that does it. I somehow thought all was not a valid command line argument anymore. That doesn't make sense from a backwards compatibility perspective. Thanks. =)

I'll poke around and see if I can find a solution.

[gopherbot]

Change https://go.dev/cl/433576 mentions this issue: cmd/go: prevent duplicate missing checksum error message

[gopherbot]

Change https://go.dev/cl/498122 mentions this issue: cmd/go: avoid duplicate errors in module load