cmd/go: missing checksums for dependencies of go get arguments and tests of external dependencies

[matloob]

cc @bcmills

The following cmd/go script test unexpectedly passes:

cd m2
go mod tidy
cd ../m1
go mod tidy
go get -t example.com/m2/q@v1.0.0 # download everything needed to build test of m2
! go test example.com/m2/q
stderr 'missing go.sum entry for go.mod for module example.com/generics at v1.0.0'

-- m1/go.mod --
module example.com/m1

go 1.20

require example.com/m2 v1.0.0
replace example.com/m2 => ../m2
-- m1/p/p.go --
package p

import _ "example.com/m2/q"
-- m2/go.mod --
module example.com/m2

go 1.20

require example.com/generics v1.0.0
-- m2/q/q.go --
package q
-- m2/q/q_test.go --
package q

import _ "example.com/generics"

What did you expect to see?

The expected behavior is that we have all the sums we need to test a dependency package (example.com/m2/q).

What did you see instead?

There's a sum missing error.

[gopherbot]

Change https://go.dev/cl/489075 mentions this issue: cmd/go: save checksums for go.mod files needed for go version lines

[bcmills]

@gopherbot, please backport to Go 1.19 and 1.20. We should at least report a clear error for missing checksums instead of trying to build with the wrong language version.

[gopherbot]

Backport issue(s) opened: #60000 (for 1.19), #60001 (for 1.20).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.

[gopherbot]

Change https://go.dev/cl/493015 mentions this issue: [release-branch.go1.20] cmd/go: save checksums for go.mod files needed for go version lines

[gopherbot]

Change https://go.dev/cl/492983 mentions this issue: [release-branch.go1.19] cmd/go: save checksums for go.mod files needed for go version lines

[gopherbot]

Change https://go.dev/cl/492741 mentions this issue: cmd/go/internal/modload: skip reading go.mod files for imports in 'go mod tidy' of modules before 'go 1.21'

[gopherbot]

Change https://go.dev/cl/502015 mentions this issue: cmd/go: omit checksums for go.mod files needed for go version lines more often in pre-1.21 modules

[gopherbot]

Change https://go.dev/cl/502016 mentions this issue: [release-branch.go1.20] cmd/go: omit checksums for go.mod files needed for go version lines more often in pre-1.21 modules

[gopherbot]

Change https://go.dev/cl/502017 mentions this issue: [release-branch.go1.19] cmd/go: omit checksums for go.mod files needed for go version lines more often in pre-1.21 modules