From 26c32de7c9a6bb54d0144d1cc2f00cc334778cac Mon Sep 17 00:00:00 2001
From: "Bryan C. Mills" <bcmills@google.com>
Date: Fri, 12 Mar 2021 11:26:51 -0500
Subject: [PATCH] cmd/go/internal/modcmd: in 'go mod tidy', suspend go.mod
 writes until tidy

For #36460

Change-Id: Ia8633f37aec8c7ed532bf7278867251e5e2a4285
Reviewed-on: https://go-review.googlesource.com/c/go/+/301370
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>
Reviewed-by: Jay Conrod <jayconrod@google.com>
---
 src/cmd/go/internal/modcmd/tidy.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/cmd/go/internal/modcmd/tidy.go b/src/cmd/go/internal/modcmd/tidy.go
index 34ff86ff185..33ecd80bcb5 100644
--- a/src/cmd/go/internal/modcmd/tidy.go
+++ b/src/cmd/go/internal/modcmd/tidy.go
@@ -60,6 +60,7 @@ func runTidy(ctx context.Context, cmd *base.Command, args []string) {
 	// request that their test dependencies be included.
 	modload.ForceUseModules = true
 	modload.RootMode = modload.NeedRoot
+	modload.DisallowWriteGoMod() // Suppress writing until we've tidied the file.
 
 	modload.LoadPackages(ctx, modload.PackageOpts{
 		Tags:                     imports.AnyTags(),
@@ -72,5 +73,7 @@ func runTidy(ctx context.Context, cmd *base.Command, args []string) {
 
 	modload.TidyBuildList()
 	modload.TrimGoSum()
+
+	modload.AllowWriteGoMod()
 	modload.WriteGoMod()
 }