Failing test will point to non-existing file if the t.Error() ocured in a different dir

[h9jiang]

This is a follow up issue from feedback collected from GopherCon.

 /example/ tree
.
├── example_test.go // the test function will call a helper function from foo/internal.go 
├── example.go
├── foo
│   └── internal.go // foo/internal.go will call t.Error()
└── internal.go // but this is the file get opened

-- example_test.go --
package example

import (
	"helloworld/example/foo"
	"testing"
)

func TestFoo(t *testing.T) {
	foo.TestHelper(t)
}

-- foo/internal.go --
func TestHelper(t *testing.T) {
	t.Errorf("asdas internal")
}

-- internal.go --
package example

// asdasd
// asdasd
// asdasd
// asdasd
// asdasd
// asdasd
// asdasd
// asdasd
// asdasd

Run the test from test explorer, and click the failing test case in test explorer. VSCode-Go will open the example/internal.go instead of the real failure at example/foo/internal.go.

It more confusing if the file example/internal.go does not exist. VSCode will say "file not found".

[h9jiang]

The reason is, vscode-go use the current dir and the return value from go test, join them together and consider it is the file that error occurred. See source.

Upon failure like this, the go test is printing only the base (file name) internal.go instead of foo/internal.go (the relative path) which cause vscode-go think example/internal.go is the place that hit this error. See source.

 ~/example/ go test -v ./...               
=== RUN   TestFoo
    internal.go:6: asdas internal
--- FAIL: TestFoo (0.00s)
FAIL
FAIL    helloworld/example      0.208s
?       helloworld/example/foo  [no test files]

cc @matloob see if it is possible to change the go test behavior to print the relative path.

If configured through -test.fullpath, the test explorer is able to find the right location to foo/internal.go.

cc @firelizzard18

[h9jiang]

After reading golang/go#21119 and golang/go#37708, I think there is really nothing we can do to change the default behavior. So we should not rely on join the path (current dir, file name) from the go test instead try using fullpath whenever possible.

By looking at the telemetry data, I can still observe a small portion of users are still using go version that is lower than 1.21 which is when the fullpath support was added.

[firelizzard18]

Prior to -test.fullpath we basically can't do anything. IIRC go test blindly truncates paths without regards to what directories those files are in and nothing we do can change that. If the user is using Go 1.21, then we can add -test.fullpath. Go Companion uses fullpath unconditionally, so I should update that to be conditional. I know I intended to add fullpath to vscode-go's test explorer but I think by the time I had time for contributing again I was focused on rewriting the test explorer (aka Go Companion).

[h9jiang]

@firelizzard18 thanks! I understand the intention of focusing on the Go Companion. I think the vscode-go now require users to use go 1.21 (at least for the latest version of the extension). I just need to find the right documentation of the version support.

I think VSCode-Go should also use the fullpath unconditionally since go 1.21 is the lowest version supported. With the go1.25 released, I think it should be go1.23 now.

I will make the change once I confirm the version support for vscode-go.