make check-windows fails and no test file under windows/ or ui/ can be compiled #59

make check-windows fails its second line on master, and no test file under
windows/ or ui/ can be compiled at all. This is independent of the
chart.v type-inference breakage; I will report that separately.

What happens

$ make check-windows
$ v -enable-globals -os windows -check windows/ui_windows_test.v
windows/ui_windows_test.v:23:36: error: unknown type `ui2.KeyCode`
  23 |     assert windows_virtual_key(.left) == .left
windows/ui_windows_test.v:30:30: error: unknown type `ui2.Kind`
  30 |     assert windows_widget_kind(.screen) == .screen
...
windows/ui_windows_test.v:344:3: error: unknown function: menu_update_window
windows/ui_windows_test.v:356:10: error: unknown function: native_window_handle

Both lines fail, the first because of chart.v (reported separately) and the
second as described here. Reproduced on a clean ce4af81 with the official
0.5.2 release binaries that ci.yml pins.

Cause

V resolves a module's root directory from the directory of the input file, not
from v.mod. ui2's v.mod declares:

Module {
	name: 'ui2'
	subdirs: ['ui', 'appkit', 'uikit', 'windows', 'linux']
}

but that does not bring the sibling directories into the compilation when the
input file is inside one of them. So:

• a test under ui/ compiles ui/*.v and cannot see windows/*.v — hence
  unknown function: menu_win32_set_menu_bar in ui/menu_windows.c.v, which
  calls into windows/menu_windows.v;
• a test under windows/ compiles windows/*.v and cannot see ui/*.v —
  hence every unknown type ui2.KeyCode / ui2.Kind / ui2.Element above.

Pointing at the module root instead does work:

$ v -enable-globals -shared -os windows -check .   # whole module, all directories

and a test file placed at the repository root sees both sides at once. That is
why the tests in #54–#57 live in embed_test.v and menu_tray_test.v at the
root rather than beside the code.

Affected files

Every *_test.v under a subdirectory:

• ui/menu_test.v — compiles on -os linux/-os android, fails on
  -os windows because ui/menu_windows.c.v calls into windows/
• windows/ui_windows_test.v — fails on every host
• ui/ui_custom_test.v — fails on every host, and separately does not parse on
  0.5.2 at all: map[string]bool{ 'field': true } (line 44 on master) is
  rejected with explicit map initialization does not support parameters

Note that ci.yml only runs ui/vml_menu_test.v, ui/ui_scroll_immediate_test.v
and examples/build_examples.vsh, which is why this has gone unnoticed: CI
never compiles windows/ui_windows_test.v or ui/menu_test.v, and make test
(v test .) sweeps all 138 test files including the macOS-only ones, so it is
not usable as a single green/red signal on Windows either.

Options

I don't have a strong opinion on which is right, and this is the maintainer's
call. Some possibilities:

1. Move the affected test files to the module root, where they compile. This is
   what Add native_window_handle for embedders, publish real NSWindow on macOS #54–Cover vails menu and tray scenarios on the Windows backend #57 do for their own tests.
2. Add the subdirectories to the module's compilation another way, if V has a
   mechanism I have not found.
3. Accept it and only run these through -check from the root, as
   make check-windows already tries to do for its first line.

Whichever way it goes, make check-windows should be green before it can be
used as a gate. I can help with any of these — just say which.