[MANIFEST] Does not work with port-overlay feature.

[Neumann-A]

Since vcpkg always throws an error if a port from an overlay is installed and the overlay is not fed into the vcpkg call.
Furthermore ports from an overlay can also not currently be installed since this is missing from the toolchain.

vcpkg/scripts/buildsystems/vcpkg.cmake

Lines 278 to 290 in 8133cef

	if(VCPKG_MANIFEST_MODE AND VCPKG_MANIFEST_INSTALL AND NOT _CMAKE_IN_TRY_COMPILE)
	execute_process(
	COMMAND "${_VCPKG_ROOT_DIR}/vcpkg${_VCPKG_EXECUTABLE_SUFFIX}" install
	--triplet ${VCPKG_TARGET_TRIPLET}
	--vcpkg-root ${_VCPKG_ROOT_DIR}
	--x-manifest-root=${_VCPKG_MANIFEST_DIR}
	--x-install-root=${_VCPKG_INSTALLED_DIR}
	--binarycaching
	RESULT_VARIABLE _VCPKG_INSTALL_RESULT)
	if (NOT _VCPKG_INSTALL_RESULT EQUAL 0)
	message(FATAL_ERROR "vcpkg install failed")
	endif()
	set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS

I would also suggest to move all code related to manifests into a separate cmake file for better separation from what the toolchain normally should do. (Manifests are just a modular addition to it.)

[strega-nil]

Is this a bug, or is it a feature request? Does this break anybody, or is it just that manifests don't work with overlay ports just yet?

[Neumann-A]

The problem is if somebody tries to use manifests with a vcpkg which has an (unknown to master) port installed from a port-overlay vcpkg will throw and error on the execution of the command.
Has such you might not be immediately breaking someone but locally sharing vcpkg instances becomes a bit more difficult if you have projects which could use the manifest but have other projects which requires ports from an overlay.

[strega-nil]

This shouldn't happen, since the installed directories aren't shared -- if blah is installed from an overlay in vcpkg/installed, then proj/vcpkg_installed can't know or care about blah, since it's a different installed tree.

[Neumann-A]

Closing since there is a way to define overlays via cmake now and registries will also solve this.