From 30119bcca997d154e4ab200b01afa7007b088994 Mon Sep 17 00:00:00 2001
From: "Bryan C. Mills" <bcmills@google.com>
Date: Fri, 16 Oct 2020 21:57:46 -0400
Subject: [PATCH] cmd/go/internal/modload: fix sort condition in
 (*replacementRepo).Versions
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In CL 258220 I added replacement versions to the repo versions used in
the modload.Query functions. The versions are computed from a map in
the modfile index, which has a nondeterministic iteration order.

I added a short-circuit condition to skip sorting in the (vastly
common) case where no replacement versions are added. However, while
cleaning up the change I accidentally deleted the line of code that
sets that condition. As a result, the test of that functionality
(mod_get_replaced) has been failing nondeterministically.

This change fixes the condition by comparing the slices before and
after adding versions, rather than by setting a separate variable.
The test now passes reliably (tested with -count=200).

Updates #41577
Updates #41416
Updates #37438
Updates #26241

Change-Id: I49a66a3a5510da00ef42b47f20a168de66100db6
Reviewed-on: https://go-review.googlesource.com/c/go/+/263266
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
---
 src/cmd/go/internal/modload/query.go            | 6 +++---
 src/cmd/go/testdata/script/mod_get_replaced.txt | 9 +++++----
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/cmd/go/internal/modload/query.go b/src/cmd/go/internal/modload/query.go
index d16a247f72..3b27e66d01 100644
--- a/src/cmd/go/internal/modload/query.go
+++ b/src/cmd/go/internal/modload/query.go
@@ -891,12 +891,12 @@ func (rr *replacementRepo) ModulePath() string { return rr.repo.ModulePath() }
 // Versions returns the versions from rr.repo augmented with any matching
 // replacement versions.
 func (rr *replacementRepo) Versions(prefix string) ([]string, error) {
-	versions, err := rr.repo.Versions(prefix)
+	repoVersions, err := rr.repo.Versions(prefix)
 	if err != nil && !errors.Is(err, os.ErrNotExist) {
 		return nil, err
 	}
 
-	added := false
+	versions := repoVersions
 	if index != nil && len(index.replace) > 0 {
 		path := rr.ModulePath()
 		for m, _ := range index.replace {
@@ -906,7 +906,7 @@ func (rr *replacementRepo) Versions(prefix string) ([]string, error) {
 		}
 	}
 
-	if !added {
+	if len(versions) == len(repoVersions) { // No replacement versions added.
 		return versions, nil
 	}
 
diff --git a/src/cmd/go/testdata/script/mod_get_replaced.txt b/src/cmd/go/testdata/script/mod_get_replaced.txt
index 0b82eb7f4f..2e2dc51ca7 100644
--- a/src/cmd/go/testdata/script/mod_get_replaced.txt
+++ b/src/cmd/go/testdata/script/mod_get_replaced.txt
@@ -19,7 +19,7 @@ go get -d example.com/x
 go list -m example.com/x
 stdout '^example.com/x v0.2.0 '
 
-go get -d example.com/x@'<v0.2.0'
+go get -d example.com/x@<v0.2.0
 go list -m example.com/x
 stdout '^example.com/x v0.1.0 '
 
@@ -36,13 +36,14 @@ go list -m example.com/x
 stdout '^example.com/x v0.0.0-00010101000000-000000000000 '
 
 # If specific-version replacements exist, the highest matching version should be used.
-go mod edit -replace=example.com/x@v0.1.0=./x -replace=example.com/x@v0.2.0=./x
+go mod edit -replace=example.com/x@v0.1.0=./x
+go mod edit -replace=example.com/x@v0.2.0=./x
 
 go get -d example.com/x
 go list -m example.com/x
 stdout '^example.com/x v0.2.0 '
 
-go get -d example.com/x@'<v0.2.0'
+go get -d example.com/x@<v0.2.0
 go list -m example.com/x
 stdout '^example.com/x v0.1.0 '
 
@@ -69,7 +70,7 @@ go get -d rsc.io/quote@v1.3
 go list -m rsc.io/quote
 stdout '^rsc.io/quote v1.3.1 '
 
-go get -d rsc.io/quote@'>v1.3.1'
+go get -d rsc.io/quote@>v1.3.1
 go list -m rsc.io/quote
 stdout '^rsc.io/quote v1.4.0'
 
-- 
2.48.1