[bug] system package manager install_substitutes method does not work in check mode

[weatherhead99]

Environment details

• Operating System+version: openSUSE Leap 15.4 (linux)
• Compiler+version: gcc-11
• Conan version: 2.0.3
• Python version: 3.9.16

when using a recipe installing system requirements which uses the "install_substitutes" method of system package manager (specifically Zypper, have not tested others), when the conan config tools.system.package_manager:mode=check, the command fails even if one of the substitutes is already installed

note in the log below the package names appear a little bit mangled somehow (i.e. including the square brackets)

Steps to reproduce

create basic conan file recipe:

from conan import ConanFile
from conan.tools.system.package_manager import Zypper

class BasicConanfile(ConanFile):
    name = "pkg"
    version = "1.0"

    def system_requirements(self):
        tool = Zypper(self)
        tool.install_substitutes([["nonexistant_library", "systemd-devel"]], update=True, check=True)

try to install this dependency with package manager in check mode :

conan install . -c tools.system.package_manager:mode=check

Logs

======== Input profiles ========
Profile host:
[settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.cppstd=gnu14
compiler.libcxx=libstdc++11
compiler.version=11
os=Linux
[conf]
tools.system.package_manager:mode=check
[buildenv]
CC=/usr/bin/gcc-11
CXX=/usr/bin/g++-11

Profile build:
[settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.cppstd=gnu14
compiler.libcxx=libstdc++11
compiler.version=11
os=Linux
[conf]

[buildenv]
CC=/usr/bin/gcc-11
CXX=/usr/bin/g++-11


======== Computing dependency graph ========
Graph root
    conanfile.py (pkg/1.0): /home/danw/Software/conan_test_sysreq/conanfile.py

======== Computing necessary packages ========
conanfile.py (pkg/1.0): RUN: rpm -q ['nonexistant_library', 'systemd-devel']
package [nonexistant_library, is not installed
package systemd-devel] is not installed

conanfile.py (pkg/1.0): WARN: Command 'rpm -q ['nonexistant_library', 'systemd-devel']' failed
ERROR: conanfile.py (pkg/1.0): Error in system_requirements() method, line 10
        tool.install_substitutes([["nonexistant_library", "systemd-devel"]], update=True, check=True)
        ConanException: None of the installs for the package substitutes succeeded.

[weatherhead99]

ok, have discovered I was using this wrong. The correct conanfile line should be:
tool.install_substitutes(["nonexistant_library"], ["systemd-devel"], update=True, check=True)

rather than:
tool.install_substitutes([["nonexistant_library", "systemd-devel"]], update=True, check=True)

however, this issue still stands because the example given in the documentation is
"
install_substitutes(packages_substitutes, update=False, check=True): try to install the list of lists of substitutes packages passed as a parameter, e.g., [["pkg1", "pkg2"], ["pkg3"]]. "

which would not actually work.

[memsharded]

Thanks @weatherhead99 for reporting this.

Yes, you found the right syntax. Indeed a clarification or better explanation would benefit the docs, so I am moving this ticket to the docs repo to fix it there.

[CJCombrink]

I have also now tripped over this: I see the docs in the code is at least correct: https://github.com/conan-io/conan/blob/develop2/conan/tools/system/package_manager.py#L99

Will try to call the install() method with several lists of packages passed as a
variable number of parameters.