cmd/go: unclear when packages have missing test coverage with 1.22

[rashokkumartce]

Go version

go1.22rc1 darwin/amd64

Output of go env in your module/workspace:

N/A

What did you do?

Created a go file with a couple of interfaces with some method signatures and a variable declaration only

What did you see happen?

[no test files]

What did you expect to see?

coverage: 0.0% of statements

[Jorropo]

Can you show the output of tree in your project and the CLI command you used ?

[rashokkumartce]

Go1.22_Issues.docx
Please check the file for the detailed information

[mvdan]

A word document is not a good way to show what you're doing.

Did you try to search past issues about this? For example #24570, but in particular #25492. It seems to me like this is working as expected.

I'm going to close this as a duplicate of #25492 for now.

[ChrisHines]

@mvdan I am not sure this should be closed for those reasons because the issue is against Go 1.22rc1 and the draft release notes say:

go test -cover now prints coverage summaries for covered packages that do not have their own test files. Prior to Go 1.22 a go test -cover run for such a package would report

? mymod/mypack [no test files]

and now with Go 1.22, functions in the package are treated as uncovered:

mymod/mypack coverage: 0.0% of statements

[mvdan]

That seems to be from https://go-review.googlesource.com/c/go/+/495447, which is for #24570, one of the earlier issues I linked. This seems to be working as intended; the author here doesn't mention any declared functions with bodies, so there aren't any lines to be covered. Although it's hard to tell because they haven't been very clear about what they are actually doing.

cc @thanm, perhaps the release notes should be made clearer. I'll reopen the issue for that purpose.

[ChrisHines]

@mvdan Thanks. I work with the issue author. They are new to Go and this is the first issue they have submitted. :) We'll get the proper details added here soon.

[ChrisHines]

The end result may turn out to be working-as-intended, but we weren't sure.

[rashokkumartce]

Here is the sample code that is giving the [no test files] as coverage result

sampleInterface.go

package main

import "sync"

type shape interface {
	area(wc *sync.WaitGroup)
	volume()
}

var x = 4

Upon executing the following command
$ go test -count=1 -coverprofile cover.out
and i'm getting the following result printed
? mydomain.com [no test files]

The package just contains the interface and we are trying to execute the command against the package, we are getting the above said result
sampleinterface.go.zip

[thanm]

@rashokkumartce thanks for posting the code in question.

As @mvdan mentioned earlier, this Go file doesn't contain any executable statements, so we can't really meaningfully express a code coverage percentage for it. Code coverage is (at some abstract level) N / M, where N is the number of statement lines executed when the tests are run, and M is the number of statement lines defined. For this case M is zero, which renders the N/M ratio invalid.

If were were to report "mymod/mypack coverage: 0.0% of statements" for this package, this would imply (incorrectly) that the package does contain some executable code and the tests for the package don't trigger the execution of that code, which is definitely not the case for this package.

I'll send a CL to tweak the release notes.

[gopherbot]

Change https://go.dev/cl/561337 mentions this issue: relnotes: tweak coverage testing notes