Multiple versions of Python available to CMake in shell.nix environment

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1

I am trying to built application that will be possible to load Python as shared library. For some reasons I need for this only Python headers of specific version.

CMakeLists.txt:

CMAKE_MINIMUM_REQUIRED(VERSION 3.5)
PROJECT(MDTest)

SET(CMAKE_EXPORT_COMPILE_COMMANDS ON)

SET(CMAKE_CXX_STANDARD 11)
SET(CXX_STANDARD_REQUIRED ON)
SET(CMAKE_CXX_EXTENSIONS OFF)

FIND_PACKAGE(Python3 REQUIRED COMPONENTS Development)

ADD_EXECUTABLE(mdtest main.cpp)

TARGET_INCLUDE_DIRECTORIES(mdtest PRIVATE ${Python3_INCLUDE_DIRS})
TARGET_LINK_LIBRARIES(mdtest PRIVATE dl)

shell.nix

{ pkgs ? import <nixpkgs>{} }:
with import <nixpkgs>{};
let
in pkgs.mkShell {
  buildInputs = with pkgs; [
    ccls
    clang-tools
    cmake
    gdb
    gcc
    fish
    mono

    python37Full
    tcl
    tk
  ];

  inputsFrom = with pkgs; [
  ];

  runScript = "fish";
}

Makefile:

BUILD_DIR      := ./build
CONFIGURATION  ?= Debug
OUTPUT_DIR     := ./output
EXECUTABLE_DIR ?= $(BUILD_DIR)/$(CONFIGURATION)

.PHONY: all
all: configure build

.PHONY: configure
configure:
	@echo '{{{Start configuring}}}'
	@mkdir --parents $(BUILD_DIR) \
			&& cmake ./CMakeLists.txt \
					-B$(BUILD_DIR) \
					-DCMAKE_BUILD_TYPE=$(CONFIGURATION)
	@cp $(BUILD_DIR)/compile_commands.json ./

.PHONY: build
build:
	@echo '{{{Start building all}}}'
	@cmake \
			--build ${BUILD_DIR} \
			--config $(CONFIGURATION) \
			--parallel \
			-- --silent # build-tool options

.PHONY: clean
clean:
	@rm --recursive --force $(BUILD_DIR)
	@rm --force ./compile_commands.json

In shell.nix environment python --version returns 3.7.15. In user environment it returns 3.9.15
But during building without specifing of Python version in CMake it found Python 3.9.19.

I understand that this question is more about CMake, but I am waiting that shell.nix environment will contains only it’s own Python.

NixOS 22.05.4267.f42a45c015f used.

2

On stackoverflow somebody said that nix-shell` doesn’t hide the outside environment by default.

Problem solved.