# This test illustrates a case where downgrading one module may upgrade another.
# Compare to the downcross1 test case in cmd/go/internal/mvs/mvs_test.go.

# The package import graph used in this test looks like:
#
# a ---- b
#   \     \
#    \     \
#     ----- c ---- d
#
# The module dependency graph originally looks like:
#
# a ---- b.2
#   \      \
#    \      \
#     ----- c.1 ---- d.2
#
# b.1 ---- c.2
#
# If we downgrade module d to version 1, we must downgrade b as well.
# If that downgrade selects b version 1, we will upgrade module c to version 2.

cp go.mod go.mod.orig
go mod tidy
cmp go.mod.orig go.mod

# Downgrading d to version 1 downgrades b, which upgrades c.
go get example.com/d@v0.1.0
go list -m all
stdout '^example.com/b v0.1.0 '
stdout '^example.com/c v0.2.0 '
stdout '^example.com/d v0.1.0 '
cmp go.mod go.mod.down1

# Restoring c to version 1 upgrades d to meet c's requirements.
go get example.com/c@v0.1.0
go list -m all
! stdout '^example.com/b '
stdout '^example.com/c v0.1.0 '
stdout '^example.com/d v0.2.0 '
cmp go.mod go.mod.down2

# If a user explicitly requests the incompatible versions together,
# 'go get' should explain why they are not compatible.
! go get example.com/c@v0.1.0 example.com/d@v0.1.0
stderr '^go: example\.com/c@v0\.1\.0 requires example\.com/d@v0\.2\.0, not example\.com/d@v0\.1\.0'

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

go 1.15

require (
	example.com/b v0.2.0
	example.com/c v0.1.0
)

replace (
	example.com/b v0.1.0 => ./b1
	example.com/b v0.2.0 => ./b2
	example.com/c v0.1.0 => ./c1
	example.com/c v0.2.0 => ./c2
	example.com/d v0.1.0 => ./d
	example.com/d v0.2.0 => ./d
)
-- go.mod.down1 --
module example.com/a

go 1.15

require (
	example.com/b v0.1.0
	example.com/c v0.2.0
	example.com/d v0.1.0 // indirect
)

replace (
	example.com/b v0.1.0 => ./b1
	example.com/b v0.2.0 => ./b2
	example.com/c v0.1.0 => ./c1
	example.com/c v0.2.0 => ./c2
	example.com/d v0.1.0 => ./d
	example.com/d v0.2.0 => ./d
)
-- go.mod.down2 --
module example.com/a

go 1.15

require example.com/c v0.1.0

replace (
	example.com/b v0.1.0 => ./b1
	example.com/b v0.2.0 => ./b2
	example.com/c v0.1.0 => ./c1
	example.com/c v0.2.0 => ./c2
	example.com/d v0.1.0 => ./d
	example.com/d v0.2.0 => ./d
)
-- a.go --
package a

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

-- b1/go.mod --
module example.com/b

go 1.15

require example.com/c v0.2.0
-- b1/b.go --
package b

import _ "example.com/c"

-- b2/go.mod --
module example.com/b

go 1.15

require example.com/c v0.1.0
-- b2/b.go --
package b

import _ "example.com/c"

-- c1/go.mod --
module example.com/c

go 1.15

require example.com/d v0.2.0
-- c1/c.go --
package c

-- c2/go.mod --
module example.com/c

go 1.15
-- c2/c.go --
package c

-- d/go.mod --
module example.com/d

go 1.15