Build: DISABLE_CONAN Env Var broken in qiskit-aer v0.7.2

[drewrisinger]

Informations

• Qiskit Aer version: 0.7.2
• Python version: 3.7.6
• Operating system: Linux

What is the current behavior?

DISABLE_CONAN environment variable and CMake flag don't work as they should, and Conan dependencies are still searched.

Steps to reproduce the problem

Build qiskit-aer v0.7.2 with DISABLE_CONAN=1 python setup.py bdist_wheel from environment without conan.

Optional for full reproduction:

• Install Nix: curl -L https://nixos.org/nix/install | sh
• nix-build -I nixpkgs=channel:nixos-20.03 -A python3Packages.qiskit-aer https://github.com/drewrisinger/nur-packages/archive/6c2e51c322fab401bbe4c597285710f643830cb3.tar.gz

What is the expected behavior?

This should build a wheel via skbuild/cmake without conan being present.
Instead, it seems the variable DISABLE_CONAN isn't set properly. See following trace:

Grep'd CMake build w/ --trace-expand flag on (note, this was with the partial solution below applied):

/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/CMakeLists.txt(50):  if(DEFINED ENV{DISABLE_CONAN} )
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/CMakeLists.txt(51):  set(_DISABLE_CONAN_DEFAULT {DISABLE_CONAN} )
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/CMakeLists.txt(55):  option(DISABLE_CONAN Disable Conan package manager to find dependencies. If disabled, you must have all dependencies present on your system. {DISABLE_CONAN} )
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/CMakeLists.txt(57):  include(CTest )
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/.eggs/cmake-3.18.4.post1-py3.7-linux-x86_64.egg/cmake/data/share/cmake-3.18/Modules/CTest.cmake(50):  option(BUILD_TESTING Build the testing tree. ON )
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/.eggs/cmake-3.18.4.post1-py3.7-linux-x86_64.egg/cmake/data/share/cmake-3.18/Modules/CTest.cmake(54):  function(GET_VS_VERSION_STRING generator var )
--
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/CMakeLists.txt(139):  if(STATIC_LINKING )
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/CMakeLists.txt(149):  set(BACKEND_REDIST_DEPS  )
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/CMakeLists.txt(150):  setup_dependencies()
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/cmake/dependency_utils.cmake(16):  if(DISABLE_CONAN )
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/cmake/dependency_utils.cmake(18):  else()
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/cmake/dependency_utils.cmake(19):  include(conan_utils )
/tmp/nix-build-python3.7-qiskit-aer-0.7.2.drv-2/source/cmake/conan_utils.cmake(1):  include(conan )

Full build log: https://gist.github.com/drewrisinger/de63a783861c28d14186714938e7029f

Suggested solutions

Partial solution:

• Replace ENV{DISABLE_CONAN} variable read in CMakeLists.txt with proper syntax: $ENV{DISABLE_CONAN}. Tested with this patch and it still didn't fix it. Ref (only second instance should be replaced):

  qiskit-aer/CMakeLists.txt

  Lines 50 to 54 in 1dbb97e

  	if(DEFINED ENV{DISABLE_CONAN})
  	set(_DISABLE_CONAN_DEFAULT ENV{DISABLE_CONAN})
  	else()
  	set(_DISABLE_CONAN_DEFAULT OFF)
  	endif()

Relevant issues:

#999, #1069 , #757, #877