cmd/go/internal/modload: fix (*mvsReqs).Max when the second argument is the empty string
As far as I can tell, this bug had gone unnoticed because everything
that uses Max so far happened to only ever present the empty string as
the first argument.
For #37438
Change-Id: Ie8c42313157d2c2c17e4058c53b5bb026b95a1c1
Reviewed-on: https://go-review.googlesource.com/c/go/+/266860
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
diff --git a/src/cmd/go/internal/modload/mvs.go b/src/cmd/go/internal/modload/mvs.go
index 94373bc..045cbea 100644
--- a/src/cmd/go/internal/modload/mvs.go
+++ b/src/cmd/go/internal/modload/mvs.go
@@ -58,7 +58,7 @@
// be chosen over other versions of the same module in the module dependency
// graph.
func (*mvsReqs) Max(v1, v2 string) string {
- if v1 != "" && semver.Compare(v1, v2) == -1 {
+ if v1 != "" && (v2 == "" || semver.Compare(v1, v2) == -1) {
return v2
}
return v1
diff --git a/src/cmd/go/internal/modload/mvs_test.go b/src/cmd/go/internal/modload/mvs_test.go
new file mode 100644
index 0000000..0cb376e
--- /dev/null
+++ b/src/cmd/go/internal/modload/mvs_test.go
@@ -0,0 +1,33 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package modload_test
+
+import (
+ "testing"
+
+ "cmd/go/internal/modload"
+)
+
+func TestReqsMax(t *testing.T) {
+ type testCase struct {
+ a, b, want string
+ }
+ reqs := modload.Reqs()
+ for _, tc := range []testCase{
+ {a: "v0.1.0", b: "v0.2.0", want: "v0.2.0"},
+ {a: "v0.2.0", b: "v0.1.0", want: "v0.2.0"},
+ {a: "", b: "v0.1.0", want: ""}, // "" is Target.Version
+ {a: "v0.1.0", b: "", want: ""},
+ {a: "none", b: "v0.1.0", want: "v0.1.0"},
+ {a: "v0.1.0", b: "none", want: "v0.1.0"},
+ {a: "none", b: "", want: ""},
+ {a: "", b: "none", want: ""},
+ } {
+ max := reqs.Max(tc.a, tc.b)
+ if max != tc.want {
+ t.Errorf("Reqs().Max(%q, %q) = %q; want %q", tc.a, tc.b, max, tc.want)
+ }
+ }
+}
