The test adapter should ignore underscored packages

[firelizzard18]

Given the following project:

• go.mod
• foo
  • foo_test.go
• _bar
  • bar_test.go

If I run go test ./..., the underscored package (_bar) is skipped. I can run those tests by running go test ./_bar so they're not completely disabled, but ... evidently does not resolve underscored packages.

However the test resolver does resolve underscored packages. I think it's OK for underscored packages to appear in the test explorer, since Go does let you build/test those packages, but they should be skipped when running all tests. Though maybe there should be a setting to control whether they're resolved at all. If they are resolved but skipped, that would need to be handled by GoTestRunner.run IIRC. This issue is reproduced by this project.

$ go list ./...
underscore-test/foo

[firelizzard18]

@hyangah do you have an opinion on whether underscored packages should be completely ignored (excluded by the resolver) or simply skipped if they're not explicitly selected, like benchmarks?

[hyangah]

Surprised to learn that go test ./_bar works. I wonder how common this type of
project structure is common.

Files whose names begin with "_" or "." are ignored
according to https://pkg.go.dev/cmd/go#hdr-Test_packages
and many people depend on this to avoid unnecessary scanning.
I am inclined to align with the go's behavior and skip _ or . prefixed
directories. (testdata too).

[firelizzard18]

In my case there was some old code I wanted to continue referencing but not maintaining, so I underscored it. I discovered this issue because another developer used "Run all tests" and a test failed (and apparently the package still builds). I've done this a few other times, but in every case my assumption was that it would be totally ignored given that gopls and go build ignored it.

[firelizzard18]

If this is still a problem after #3523, it needs to be fixed in gopls