Add possibility to add replace to the generated go.mod

[chaudum]

Certain projects have the need for defining replace directives in their go.mod to build.

I've tried to use the --with argument to pass additional replace directives:

XK6_SKIP_CLEANUP=1 xk6 build \
  --with k8s.io/client-go="k8s.io/client-go v0.21.0" \
  --with k8s.io/api="k8s.io/api v0.21.0" \
  --with github.com/chaudum/xk6-loki="$(pwd)"

This will correctly add replaces in the resulting go.mod:

module k6

go 1.16

replace k8s.io/client-go => k8s.io/client-go v0.21.0

replace k8s.io/api => k8s.io/api v0.21.0

replace github.com/chaudum/xk6-loki => /home/christian/sandbox/chaudum/xk6-loki

require go.k6.io/k6 latest

However it also adds imports in the main.go:

package main

import (
	k6cmd "go.k6.io/k6/cmd"

	// plug in k6 modules here
	// TODO: Create /modules/standard dir structure?
	// _ "go.k6.io/k6/modules/standard"
	_ "k8s.io/client-go"
	_ "k8s.io/api"
	_ "github.com/chaudum/xk6-loki"
)

func main() {
	k6cmd.Execute()
}

The problem with these imports is, that there are no top-level packages for e.g. k8s.io/client-go,
resulting in the following error:

go: finding module for package k8s.io/client-go
k6 imports
	k8s.io/client-go: module k8s.io/client-go@latest found (v0.0.0-00010101000000-000000000000, replaced by k8s.io/client-go@v0.21.0), but does not contain package k8s.io/client-go

Removing the imports and running go mod tidy && go build -o xk6-loki main.go in the build environment manually solves the problem.

I would like to suggest to add an option to add replace directives without adding the package imports to the main.go file. This could for example be done with a separate --replace argument.

[imiric]

Hi, thanks for suggesting this. A new --replace argument does make sense to handle these cases.

Our resources are scarce for new xk6 features right now, but we'll try to get to this in the next few weeks. Otherwise, feel free to propose a PR :)