x/tools/goimports: enable deleting without adding missing imports

[ikonst]

Adding missing imports can take substantial time (~ 30-60 seconds in a large codebase) due to the need to load packages. This makes goimports problematic for "action on save" workflows, as saves would either block the editor or (if async) risk undoing user's work (when goimports eventually finishes and writes back the file).

I'd like to propose another flag, -delete-only, that'll produce only DeleteImport fixes, since I would assume that DeleteImport fixes can be produced quickly without loading packages either.

[gabyhelp]

Related Issues

• x/tools/cmd/goimports: add --format-only flag #31745 (closed)
• x/tools/imports: add FormatOnly option #14500 (closed)
• cmd/goimports: flag for only importing standard lib #10679 (closed)
• proposal: x/tools/cmd/goimports: add flag to remove blank lines in import for regrouping during formatting #64271
• x/tools/gopls: add a setting to control removal of unused imports, and a quickfix #54362
• x/tools/go/analysis/internal/checker: -fix should remove unneeded imports #72035 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[ikonst]

As a workaround (inspired by #10679), this seems to be functionally equivalent for us¹:

GOPATH=/dev/null GOWORK=off goimports -w somefile.go

i.e. somefile.go

package mypackage

import (
  "example.com/unused"
)

func foo() {
  unimported.Bar()
}

is transformed as

 package mypackage
-
-import (
-   "example.com/unused"
-)

 func foo() {
   unimported.Bar()
 }

Footnotes

1. we use workspaces hence GOWORK=off ↩

[adonovan]

We recently added a lot of logic to the implementation of the analyzer drivers' -fix flag so that they would delete unused imports without running go list, using the unmodified package's import mapping to provide the necessary information about which local name is defined by each import.

I am not sure yet what is the best API to expose this operation, but I agree that the library should provide it in some form.

[mateusz834]

@adonovan the linked CL has a typo?

[adonovan]

@adonovan the linked CL has a typo?

Thanks. Fixed.

[IlyasYOY]

Hey @ikonst!

I faced the same problem: running goimports would take too long to run on save.

In my use case I mitigated the issue by running it with this option: https://github.com/golang/tools/blob/acb706d0ca00af12405b5adecce5d2bcc0429af1/cmd/goimports/goimports.go#L56 goimports -format-only

In this case goimports does not try to resolve imports. I'd advise using this setting and removing unused imports manually.

[ikonst]

@IlyasYOY Thanks for the suggestion. I was actually familiar with the option, which is why I proposed to complement it with -delete-only (which assumes formatting). What I'm suggesting above also preserves formatting as well as deletion, but it's a bit hacky.