cmd/go: retain sums for replacement modules in 'go mod tidy'

Fixes #27868

Change-Id: I6c2d221c4325a2f44625e797a82735d812ee0ec1
Reviewed-on: https://go-review.googlesource.com/c/153817
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

diff --git a/src/cmd/go/internal/modcmd/tidy.go b/src/cmd/go/internal/modcmd/tidy.go
index f2063a9ea601c976d596c9581aed7144db2f605d..839c92a0a02b4433aa44a2c847b0b5ed9df48957 100644 (file)
--- a/src/cmd/go/internal/modcmd/tidy.go
+++ b/src/cmd/go/internal/modcmd/tidy.go
@@ -77,7 +77,17 @@ func modTidyGoSum() {
        keep := make(map[module.Version]bool)
        var walk func(module.Version)
        walk = func(m module.Version) {
-               keep[m] = true
+               // If we build using a replacement module, keep the sum for the replacement,
+               // since that's the code we'll actually use during a build.
+               //
+               // TODO(golang.org/issue/29182): Perhaps we should keep both sums, and the
+               // sums for both sets of transitive requirements.
+               r := modload.Replacement(m)
+               if r.Path == "" {
+                       keep[m] = true
+               } else {
+                       keep[r] = true
+               }
                list, _ := reqs.Required(m)
                for _, r := range list {
                        if !keep[r] {

diff --git a/src/cmd/go/testdata/script/mod_sum_replaced.txt b/src/cmd/go/testdata/script/mod_sum_replaced.txt
new file mode 100644 (file)
index 0000000..b03982d
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_sum_replaced.txt
@@ -0,0 +1,28 @@
+env GO111MODULE=on
+
+# After 'go get -d', the go.sum file should contain the sum for the module.
+go get -d rsc.io/quote@v1.5.0
+grep 'rsc.io/quote v1.5.0' go.sum
+
+# If we replace the module and run 'go mod tidy', we should get a sum for the replacement.
+go mod edit -replace rsc.io/quote@v1.5.0=rsc.io/quote@v1.5.1
+go mod tidy
+grep 'rsc.io/quote v1.5.1' go.sum
+cp go.sum go.sum.tidy
+
+# 'go mod vendor' should preserve that sum, and should not need to add any new entries.
+go mod vendor
+grep 'rsc.io/quote v1.5.1' go.sum
+cmp go.sum go.sum.tidy
+
+-- go.mod --
+module golang.org/issue/27868
+
+require rsc.io/quote v1.5.0
+
+-- main.go --
+package main
+
+import _ "rsc.io/quote"
+
+func main() {}