Unable to build module without verbs with a subpackage that has verbs

[matt2e]

Summary:

• Create a module, but don't define any verbs in it
• Create a subpackage in that module and define a verb
• Building the module will fail because main.go imports the module package but then doesn't use it

Detailed example:

outer.go:

package outer

import "ftl/outer/inner"

//ftl:data export
type Event struct {
	Value inner.EchoResponse
}

inner.go:

package inner

import (
	"context"
	"fmt"

	"github.com/TBD54566975/ftl/go-runtime/ftl" // Import the FTL SDK.
)

//ftl:data export
type EchoRequest struct {
	Name ftl.Option[string] `json:"name"`
}

//ftl:data export
type EchoResponse struct {
	Message string `json:"message"`
}

//ftl:verb export
func Echo(ctx context.Context, req EchoRequest) (EchoResponse, error) {
	return EchoResponse{Message: fmt.Sprintf("Hello, %s!", req.Name.Default("anonymous"))}, nil
}

Building this module generates .ftl/go/main/main.go:

// Code generated by FTL. DO NOT EDIT.
package main

import (
	"context"

	"github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/ftlv1connect"
	"github.com/TBD54566975/ftl/common/plugin"
	"github.com/TBD54566975/ftl/go-runtime/server"

	"ftl/outer"
	"ftl/outer/inner"
)

func main() {
	verbConstructor := server.NewUserVerbServer("outer",
		server.HandleCall(inner.Echo),
	)
	plugin.Start(context.Background(), "outer", verbConstructor, ftlv1connect.VerbServiceName, ftlv1connect.NewVerbServiceHandler)
}

Which results in the error:
./main.go:11:2: "ftl/outer" imported and not used