[dev.cmdgo] cmd/go: maintain a go.work.sum file

This change causes the go command to maintain a separate go.work.sum
file when in workspace mode rather than using the go.sum files
from the individual modules. This isn't quite what the proposal
spec specifies, which is that the sums that don't exist in any
of the workspace modules are added to go.work.sum rather than
the necessary sums. That will be done in a future change.

Change-Id: I528b9b153a93a4cd67c5af471ad6d5bd3628578b
Reviewed-on: https://go-review.googlesource.com/c/go/+/334939
Trust: Michael Matloob <matloob@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/cmd/go/internal/modload/import.go b/src/cmd/go/internal/modload/import.go
index b6b9bf65b8..773d8b600b 100644
--- a/src/cmd/go/internal/modload/import.go
+++ b/src/cmd/go/internal/modload/import.go
@@ -32,6 +32,8 @@ type ImportMissingError struct {
 	Module   module.Version
 	QueryErr error
 
+	ImportingModule module.Version
+
 	// isStd indicates whether we would expect to find the package in the standard
 	// library. This is normally true for all dotless import paths, but replace
 	// directives can cause us to treat the replaced paths as also being in
@@ -673,7 +675,7 @@ func fetch(ctx context.Context, mod module.Version, needSum bool) (dir string, i
 		mod = r
 	}
 
-	if HasModRoot() && cfg.BuildMod == "readonly" && needSum && !modfetch.HaveSum(mod) {
+	if HasModRoot() && cfg.BuildMod == "readonly" && !inWorkspaceMode() && needSum && !modfetch.HaveSum(mod) {
 		return "", false, module.VersionError(mod, &sumMissingError{})
 	}