cmd/go/internal/modfetch: prevent duplicate hashes in go.sum
To write go.sum, each module and then each hash is looped through. The
hashes are kept in a slice and there is no check to ensure that hashes
were not added or already exist in the file. Therefore, unique the
hashes of each module before writing to prevent duplicates.
Fixes: #28456
Change-Id: I1cf7e7cdee3e7530a0ee605cd76d738627be1e0d
GitHub-Last-Rev: 0ed02e9591e966fe5f6ba275635c3974daa2656e
GitHub-Pull-Request: golang/go#53291
Reviewed-on: https://go-review.googlesource.com/c/go/+/411154
Auto-Submit: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/src/cmd/go/internal/modfetch/fetch.go b/src/cmd/go/internal/modfetch/fetch.go
index a7c8c2c..426df9b 100644
--- a/src/cmd/go/internal/modfetch/fetch.go
+++ b/src/cmd/go/internal/modfetch/fetch.go
@@ -833,6 +833,7 @@
for _, m := range mods {
list := goSum.m[m]
sort.Strings(list)
+ str.Uniq(&list)
for _, h := range list {
st := goSum.status[modSum{m, h}]
if (!st.dirty || (st.used && keep[m])) && !sumInWorkspaceModulesLocked(m) {
diff --git a/src/cmd/go/testdata/script/mod_tidy_duplicates.txt b/src/cmd/go/testdata/script/mod_tidy_duplicates.txt
new file mode 100644
index 0000000..d454c8d
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_tidy_duplicates.txt
@@ -0,0 +1,38 @@
+env GO111MODULE=on
+
+# Regression test for golang.org/issue/28456:
+# 'go mod tidy' should not leave duplicate lines when re-writing the file.
+
+go mod tidy
+cmp go.sum golden.sum
+
+-- go.mod --
+module use
+
+go 1.16
+
+require rsc.io/quote v1.5.2
+
+-- go.sum --
+rsc.io/quote v1.5.2 h1:3fEykkD9k7lYzXqCYrwGAf7iNhbk4yCjHmKBN9td4L0=
+rsc.io/quote v1.5.2 h1:3fEykkD9k7lYzXqCYrwGAf7iNhbk4yCjHmKBN9td4L0=
+rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
+rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
+rsc.io/sampler v1.3.0 h1:HLGR/BgEtI3r0uymSP/nl2uPLsUnNJX8toRyhfpBTII=
+rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
+rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
+rsc.io/testonly v1.0.0 h1:K/VWHdO+Jv7woUXG0GzVNx1czBXUt3Ib1deaMn+xk64=
+rsc.io/testonly v1.0.0/go.mod h1:OqmGbIFOcF+XrFReLOGZ6BhMM7uMBiQwZsyNmh74SzY=
+-- golden.sum --
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c h1:pvCbr/wm8HzDD3fVywevekufpn6tCGPY3spdHeZJEsw=
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+rsc.io/quote v1.5.2 h1:3fEykkD9k7lYzXqCYrwGAf7iNhbk4yCjHmKBN9td4L0=
+rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
+rsc.io/sampler v1.3.0 h1:HLGR/BgEtI3r0uymSP/nl2uPLsUnNJX8toRyhfpBTII=
+rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
+rsc.io/testonly v1.0.0 h1:K/VWHdO+Jv7woUXG0GzVNx1czBXUt3Ib1deaMn+xk64=
+rsc.io/testonly v1.0.0/go.mod h1:OqmGbIFOcF+XrFReLOGZ6BhMM7uMBiQwZsyNmh74SzY=
+-- main.go --
+package use
+
+import _ "rsc.io/quote"
