cmd/go: 'go mod vendor' does not fail on case-insensitive import collision #38571
Description
What version of Go are you using (go version)?
$ go version go version go1.14.2 linux/amd64
Does this issue reproduce with the latest release?
Yes
What did you do?
During the investigation of #38342, I discovered the following ux quirk:
On a case insensitive filesystem: (I am using vfat)
package main
import (
_ "example.com/Foo"
_ "example.com/foo"
)
func main() {}
-- go.mod --
module play.ground
go 1.14
require (
example.com/foo v0.1.0
example.com/Foo v0.1.0
)
replace (
example.com/foo => ./foo
example.com/Foo => ./!foo
)
-- foo/go.mod --
module example.com/foo
-- foo/foo.go --
package foo
-- !foo/go.mod --
module example.com/Foo
-- !foo/foo.go --
package Foogo mod vendorWhat did you expect to see?
main.go:5:2: case-insensitive import collision: "example.com/foo" and "example.com/FOO"
What did you see instead?
go mod vendor succeeds, but go build fails, and one must flush vendor to fix things:
go buildmain.go:5:2: case-insensitive import collision: "example.com/foo" and "example.com/FOO"