Additional dependencies or prerequisite for plugins with v3.20.0

[mamo3gr]

Dear authors,

Thank you for the great framework.
I have used Goa with a plugin for a long time.
goa gen fails in some use cases with v3.20.0.

How to reproduce

The same steps with https://github.com/goadesign/goa/blob/11f1923620be3d8215b108f652031e1e4cd7ea2d/README.md#-quick-start but design/design.go is modified as below:

package design

import (
    . "goa.design/goa/v3/dsl"
    slogdriver "github.com/kitagry/goaplugin/slogdriver/dsl"
)

var _ = Service("calc", func() {
    slogdriver.HealthCheckPaths("/healthz")
})

• Just executing goa gen calcsvc/design (hereafter goa gen in short) with blank go.mod succeeds. gen directory is generated.
• Starting blank go.mod, go mod tidy and then goa gen fails with error err: exit status 1: stderr: go: updates to go.mod needed; to update it: go mod tidy.
  • Executing go mod tidy makes no sense. goa gen fails again.
  • Generating intermediate file with goa gen --debug and go mod tidy again makes goa gen succeed.
  • After generating, remove gen directory and intermediate file (goa[1-9]+
    directory), then executing go mod tidy removes github.com/gohugoio/hashstructure.

Goa v3.19.1 seems not to fail in despite of those failing procedure.
In #3642, github.com/gohugoio/hashstructure is added. I suspect that this change affect the requirement and/or prerequisite of the plugins.

Question

• Does Goa support the use case of cleaning up and re-generating with goa gen?
• If it is yes, what is the requirement plugins must fulfill?
  • I'm not an author of the plugin in the example, but can/will submit improving PR to the repository.

Kind regards,

[raphael]

Thank you for the detailed explanation and the repro. This is fixed by #3682.
TL;DR there was a missing anonymous import to force Go to add the hashstructure dependency.