cmd/go: go test -outputdir -coverprofile fails at compile time when outputdir does not exist

[nodo]

Description

go test command fails when using the flag -c, if -outpudir is set to a non-existing directory.

What version of Go are you using (go version)?

• go version go1.10 darwin/amd64
• go version devel +7e34ac1f4c Wed Mar 28 05:58:35 2018 +0000 darwin/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"

What did you do?

1. Create a dummy test file:

package main

import "testing"

func TestHelloWorld(t *testing.T) {
}

2. Compile the test file with a coverprofile and non-existing directory go test -c -cover -outputdir=./all/profiles/here -coverprofile=profile.txt
3. See the error

The command above does not report an error with go1.9.4.

What did you expect to see?

I would expect no error when compiling the test, but rather when running it (as it was prior to go1.10).

What did you see instead?

An error occurs:

open all/profiles/here/profile.txt: no such file or directory

[gopherbot]

Change https://golang.org/cl/103395 mentions this issue: cmd/go: don't try to initialize cover profile for go test -c