cmd/go: adding -cover to "go test -n" can cause spurious failures

[thanm]

On tip, invoking "go test -n -cover ./..." on a collection of packages that include at least one package with code but no tests can result in a spurious errors. Example:

$ cd `go env GOROOT`
$ cd src/internal/coverage
$ go test -n -cover ./...
...
internal/coverage/uleb128: open $WORK/b112/covmeta.b07a5f2dff1231cae3a6bdd70c8cc7c19da16abf8ac59747d8e9859c03594d37: no such file or directory
$ echo $?
1
$

This obviously shouldn't be happening for a "-n" test run (works fine without -cover).

[gabyhelp]

Similar Issues

• cmd/go: go 1.22.0: go test throws errors when processing folders not listed in coverpkg argument #65653
• cmd/go: test coverpkg=./... not ignoring folders with test only files #23454
• cmd/go: test with coverage unexpect fail #43242
• cmd/go: test coverpkg=all ./... with test only packages will fail to build #27333
• cmd/go: improperly synchronized -coverprofile output for packages with no tests #63356

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[gopherbot]

Change https://go.dev/cl/592201 mentions this issue: cmd/go: fix "go test -n -cover" glitch with no-test packages