env TESTGO_VERSION=go1.99

! go list -f '{{.Module.GoVersion}}'
stderr 'go: updates to go.mod needed'
stderr 'go mod tidy'

go mod tidy
cat go.mod
go list -f '{{.Module.GoVersion}}'
stdout 1.22

# Adding [email protected] should upgrade to Go 1.23rc1.
cp go.mod go.mod1
go get example.com/[email protected]
stderr '^go: upgraded go 1.22 => 1.23rc1\ngo: upgraded example.com/a v1.0.0 => v1.0.1\ngo: upgraded example.com/b v1.0.0 => v1.0.1$'
go list -f '{{.Module.GoVersion}}'
stdout 1.23rc1

# Repeating the update with [email protected] should use that Go version.
cp go.mod1 go.mod
go get example.com/[email protected] [email protected]
go list -f '{{.Module.GoVersion}}'
stdout 1.24.0

# Go version-constrained updates should report the problems.
cp go.mod1 go.mod
! go get example.com/[email protected] [email protected]
stderr '^go: example.com/[email protected] requires [email protected], not [email protected]$'
! go get example.com/[email protected] [email protected]
stderr '^go: example.com/[email protected] indirectly requires [email protected], not [email protected]$'
go get example.com/[email protected] [email protected]
go list -f '{{.Module.GoVersion}}'
stdout 1.28rc1
go get [email protected]
stderr '^go: downgraded go 1.28rc1 => 1.24.2$'
stderr '^go: downgraded example.com/a v1.0.2 => v1.0.1$'
stderr '^go: downgraded example.com/b v1.0.2 => v1.0.1$'
go list -f '{{.Module.GoVersion}}'
stdout 1.24.2

-- go.mod --
module m
go 1.21

require (
	example.com/a v1.0.0
	example.com/b v0.9.0
)

replace example.com/a v1.0.0 => ./a100
replace example.com/a v1.0.1 => ./a101
replace example.com/a v1.0.2 => ./a102
replace example.com/b v1.0.1 => ./b101
replace example.com/b v1.0.2 => ./b102
replace example.com/b v1.0.0 => ./b100
replace example.com/b v0.9.0 => ./b100

-- x.go --
package m

import (
	_ "example.com/a"
	_ "example.com/b"
)

-- a100/go.mod --
module example.com/a
go 1.22

require example.com/b v1.0.0

-- a100/a.go --
package a

-- a101/go.mod --
// this module is technically invalid, since the dep example.com/b has a newer go line than this module,
// but we should still be able to handle it.
module example.com/a
go 1.22

require example.com/b v1.0.1

-- a101/a.go --
package a

-- a102/go.mod --
// this module is technically invalid, since the dep example.com/b has a newer go line than this module,
// but we should still be able to handle it.
module example.com/a
go 1.25

require example.com/b v1.0.2

-- a102/a.go --
package a

-- b100/go.mod --
module example.com/b
go 1.22

-- b100/b.go --
package b

-- b101/go.mod --
module example.com/b
go 1.23rc1

-- b101/b.go --
package b

-- b102/go.mod --
module example.com/b
go 1.27

-- b102/b.go --
package b