fix redunant-import-alias rule - unused alias is also redundant

[mfederowicz]

related with: #936

I think we should change definition of redundant alias, because import like this:

import apiv2 "cloud.google.com/go/run/apiv2" is ok i one condition: when alias apiv2 is used min one time in code below import, otherwise is redundant because is not used

of course this rule checks only imports with aliases, imports without aliases are ignored in this rule :)

[denisvmedia]

Can you please improve the wording? It's not really clear for me what exactly is to be ignored.

[mfederowicz]

import apiv2 "cloud.google.com/go/run/apiv2"
import v1 "https://pkg.go.dev/k8s.io/api/core/v1"

technically above aliases are correct if they are used min one time later in code. What is your sugestion to describe that flag?

[denisvmedia]

The problem here is that if it's not used, the code won't compile.

package main

import apiv2 "cloud.google.com/go/run/apiv2"
import v1 "k8s.io/api/core/v1"
import "fmt"

func main() {
    fmt.Println("dummy")
}

$ go build .
# poc
./main.go:3:8: "cloud.google.com/go/run/apiv2" imported and not used
./main.go:4:8: "k8s.io/api/core/v1" imported and not used

[mfederowicz]

no no no, your case is not that case, because this code is not used and make "noise" after compile

but in case mentioned in #936:

package main

import (
	"fmt"
	redundant "example.com/app/redundant"
)

func main() {
	fmt.Println(redundant.Lovely)
}

=$ ./app 
123

above code is working well, but linter shows warning:

=$ cat ~/revive-aliases.toml 
ignoreGeneratedHeader = false
severity = "warning"
confidence = 0.8
errorCode = 0
warningCode = 0

[rule.blank-imports]
[rule.dot-imports]
[rule.redundant-import-alias]

revive -config ~/revive-aliases.toml -formatter stylish ./...
main.go
  (5, 2)  https://revive.run/r#redundant-import-alias  Import alias "redundant" is redundant  


 ✖ 1 problem (0 errors) (1 warnings)

after set ignoreUsed = true

[rule.redundant-import-alias]
  arguments = [{ignoreUsed = true}]

linter dont produce warnings that is the case :)

[denisvmedia]

It is indeed redundant. This is the purpose of the linter. If you think it's fine for your project, you should just disable this linter rule.

[mfederowicz]

Yes i know, it is specific case, because in one way you should think how you use packages and aliases for them. On the other side we can leave this rule with that argument for more flexibility, but this is not my decision, what you think @chavacava

[denisvmedia]

What is specific about this case? ignoreUsed seems to be essentially disabling the rule.

[mfederowicz]

@denisvmedia ok, I think that issue #936 and this pull request is to close, because in standard scenario this rule is used to detect redundant aliases, and results should used to fix/cleanup codebase of your project (change redundant aliases to proper form)