VCPKG_ROOT not defined for CMake - c++

Question

I am trying to set up vcpkg with a CMake project. Since I intend to have multiple people with different platforms working on this project, I wanted to use an Environment Variable to set CMAKE_TOOLCHAIN_FILE instead of a command line argument as recommended here for cmake: https://vcpkg.readthedocs.io/en/latest/users/integration/
However, It appears that CMake is unable to find the VCPKG_ROOT environment variable. I made a small example separate from my project to see if the problem still exists and it does. Here is my CMakeLists.txt file:
cmake_minimum_required (VERSION 3.8)
#vcpkg init
if(DEFINED ENV{VCPKG_ROOT} AND NOT DEFINED CMAKE_TOOLCHAIN_FILE)
MESSAGE("vcpkg root found")
set(CMAKE_TOOLCHAIN_FILE "$ENV{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake"
CACHE STRING "")
else()
MESSAGE("vcpkg not found")
endif()
project ("CmakeVcpkgTestF")
add_executable (CmakeVcpkgTestF "CmakeVcpkgTestF.cpp" "CmakeVcpkgTestF.h")
And here is the associated output when buliding, note that "vcpkg not found is output" instead of "vcpkg root found"
1> CMake generation started for default configuration: 'x64-Debug (default)'.
1> Command line: "cmd.exe" /c "%SYSTEMROOT%\System32\chcp.com 65001 >NUL && "C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\2019\COMMUNITY\COMMON7\IDE\COMMONEXTENSIONS\MICROSOFT\CMAKE\CMake\bin\cmake.exe" -G "Ninja" -DCMAKE_BUILD_TYPE:STRING="Debug" -DCMAKE_INSTALL_PREFIX:PATH="F:\VisualStudio2019\CmakeVcpkgTestF\out\install\x64-Debug (default)" -DCMAKE_C_COMPILER:FILEPATH="C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.28.29333/bin/Hostx64/x64/cl.exe" -DCMAKE_CXX_COMPILER:FILEPATH="C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.28.29333/bin/Hostx64/x64/cl.exe" -DCMAKE_MAKE_PROGRAM="C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\2019\COMMUNITY\COMMON7\IDE\COMMONEXTENSIONS\MICROSOFT\CMAKE\Ninja\ninja.exe" "F:\VisualStudio2019\CmakeVcpkgTestF" 2>&1"
1> Working directory: F:\VisualStudio2019\CmakeVcpkgTestF\out\build\x64-Debug (default)
1> [CMake] vcpkg not found
1> [CMake] -- Configuring done
1> [CMake] -- Generating done
1> [CMake] -- Build files have been written to: F:/VisualStudio2019/CmakeVcpkgTestF/out/build/x64-Debug (default)
1> Extracted CMake variables.
1> Extracted source files and headers.
1> Extracted code model.
1> Extracted includes paths.
1> CMake generation finished.
So far all I have done install vcpkg (running the required bootstrap as well), is there something else I need to do to get this to work? Also it is worth noting that vcpkg is installed at the root of my drive(specifically F:/vcpkg/vcpkg), not at root of the code, but I don't imagine that is causing the problem.
Thanks in advance for any assistance.

Answer 1

Based on your output, this is the second time your code has run. Your if condition asks whether CMAKE_TOOLCHAIN_FILE is defined at all, but it is! You defined it as a cache variable, which was then loaded into the global scope on the second run.
You probably want a test more like this:
set(vcpkg "$ENV{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake")
if(NOT CMAKE_TOOLCHAIN_FILE AND EXISTS "${vcpkg}")
set(CMAKE_TOOLCHAIN_FILE "${vcpkg}"
CACHE FILEPATH "CMake toolchain file")
message(STATUS "vcpkg toolchain found: ${CMAKE_TOOLCHAIN_FILE}")
endif()