bug: Using no relative path prefix produces wrong code dsl.Files

[gabyx]

Goa is awesome, but we have seen an issue which occures when doing:

	dsl.Files("/mysuperduperapi.json", "a/b/c/openapi3.json")

The code does produces ([code])(https://github.com/goadesign/examples/blob/master/basic/gen/http/calc/server/server.go#L56)

	fileSystemPkgGenHTTPOpenapi3JSON = appendPrefix(fileSystemPkgGenHTTPOpenapi3JSON, "/a/b/c")

but if the a/b/c/ is dropped, e.g. dsl.Files("/mysuperduperapi.json", "openapi3.json")

Goa does not generate the appendPrefix which does not result in selecting the openapi3.json but trying to access mysuperduperapi.json.
So I think appendPrefix should always be generate even if its with "." to select the openapi3.json.

P.S. Maybe this is also intended behavior, but its kind of odd, because only

• dsl.Files("/openapi3.json", "openapi3.json") works
• dsl.Files("/openapi.json", "openapi3.json") does not work

This is triggered by this line basically

[gabyx]

IMO: Changing

{{- if ne $prefix "/" }}
	{{ .ArgName }} = appendPrefix({{ .ArgName }}, "{{ $prefix }}")
{{- end }}

to

	{{ .ArgName }} = appendPrefix({{ .ArgName }}, "{{ $prefix }}")

should always work as the s.fs.Open(path.Join("/", name) in appendFS is not harmful.

[raphael]

Wouldn't making this change cause a different behavior when serving files from the filesystem? the path /foo isn't equivalent to foo, the Files comment documents the difference (absolute vs. relative paths).

I don't quite follow:

Goa does not generate the appendPrefix which does not result in selecting the openapi3.json but trying to access mysuperduperapi.json.

Goa should serve openapi3.json using a relative path (that is the file should live in the current directory of the service process). If Goa really attempts to serve mysuperduperapi.json then that's a bug.

Would you be able to provide a complete minimal design that reproduces the issue? that would probably help, thank you!