x/tools/gopls: invoking source.addTest from CLI fails with ENOENT

[adonovan]

While working on https://go.dev/cl/634197, I tried the new "Add test for function 'fingerprint'" code action within Emacs+eglot, and got an unhelpful "Internal error". I tried it again from the gopls CLI, and got a different error:

$ gopls codeaction -kind=source.addTest -exec ./gopls/internal/cache/methodsets/fingerprint.go:54
gopls: edits not applied because of getFile: file:///Users/adonovan/w/xtools/gopls/internal/cache/methodsets/fingerprint_test.go: open /Users/adonovan/w/xtools/gopls/internal/cache/methodsets/fingerprint_test.go: no such file or directory

Then I tried it from VS Code, and it worked great. (That said, the code action was not visible in the Command-. quick menu, and had to be selected from the right-click > Source Actions... menu. We should reinvestigate the endlessly fiddly algorithm that governs this.)

So, I don't think there's a bug in gopls' Code Action or command handler, but there is in the CLI, and in Eglot, and perhaps they are related.

[gopherbot]

Change https://go.dev/cl/635680 mentions this issue: slices,maps: delegate to go1.21 functions of the same name