x/tools/gopls: Extract function not handle anonymous functions correctly

[rogeryk]

gopls version

v14.2

go env

unimportant

What did you do?

In the following example, select all main function body, then toggle "Extract function"

func main() {
	var s []string
	slices.SortFunc(s, func(a, b string) int {
		return cmp.Compare(a, b)
	})
	println(s)
}

What did you expect to see?

func main() {
	newFunction()
}

func newFunction() {
	var s []string
	slices.SortFunc(s, func(a, b string) int {
		return cmp.Compare(a, b)
	})
	println(s)
}

What did you see instead?

func main() {
	shouldReturn := newFunction()
	if shouldReturn {
		return
	}
}

func newFunction() bool {
	var s []string
	slices.SortFunc(s, func(a, b string) int {
		return true, cmp.Compare(a, b)
	})
	println(s)
	return false
}

Editor and settings

No response

Logs

No response

[adonovan]

The bad news is that "extract function" has a lot of serious bugs that make it a use-at-your-own-peril sort of feature: notably, it discards all comments in the code that migrates. The good news is that it is a priority for our team in 2024 to improve all of our refactoring tools.

[gopherbot]

Change https://go.dev/cl/617335 mentions this issue: gopls/internal: fix extract refactor for cases with anonymous functions

[findleyr]

Thanks @golopot for this fix.