minizip-ng-config.cmake relies on non-existant zlib-ng-config.cmake

[negril]

As per https://cmake.org/cmake/help/latest/module/CMakeFindDependencyMacro.html calling find_dependency(ZLIBNG REQUIRED) requires a zlib-ng-config.cmake which zlib-ng does not install.

[negril]

Seemingly fixed in zlib-ng/zlib-ng#1601

[nmoinvaz]

Why reopened?

[parona-source]

Why reopened?

minizip-ng uses find_package(ZLIBNG QUIET) which matches zlibng-config.cmake but not zlib-ng-config.cmake. This then gets added to minizip-ng.cmake which doesn't work with zlib-ng-config.cmake.

Thinking about a change like this parona-source@982eda6. Ive to see if other distribution install FindZLIBNG systemwide without a zlib-ng package config file, meaning this change would break it for them.

[negril]

To add to that.
Relevant here is that zlib-ng installs zlib-ng-config.cmake not zlibng-config.cmake that minizip-ng tries to find in
FindZLIBNG.cmake.

cmake_minimum_required(VERSION 3.26)
project(test CXX)

find_package(minizip-ng REQUIRED)

yields

CMake Error at /usr/share/cmake/Modules/CMakeFindDependencyMacro.cmake:76 (find_package):
  By not providing "FindZLIBNG.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "ZLIBNG", but
  CMake did not find one.

  Could not find a package configuration file provided by "ZLIBNG" with any
  of the following names:

    ZLIBNGConfig.cmake
    zlibng-config.cmake

  Add the installation prefix of "ZLIBNG" to CMAKE_PREFIX_PATH or set
  "ZLIBNG_DIR" to a directory containing one of the above files.  If "ZLIBNG"
  provides a separate development package or SDK, be sure it has been
  installed.
Call Stack (most recent call first):
  /usr/lib64/cmake/minizip-ng/minizip-ng-config.cmake:37 (find_dependency)
  CMakeLists.txt:4 (find_package)


-- Configuring incomplete, errors occurred!

This is was caused by having a ZLIBNG as the internal name and then using the custom FindZLIBNG.cmake as zlib-ng used to not install zlib-ng-config.cmake.

[sgoth]

Is there any progress on this?
This breaks builds on any system that has zlib-ng installed.

I'm using minizip-ng via vcpkg. They treat zlib 1.3.1 as dependency. On a system that has zlib-ng installed systemwide, the cmake script does both: it searches ZLIBNG even though i'd like to provide ZLIB and then chokes on it due to this error.

Same version of everything else works fine on a system without system side zlib-ng installation.

This is on arch linux - they built their latest git version against zlib-ng. So i guess this will spread fast.

[Coeur]

Is it about renaming FindZLIBNG.cmake to FindZLIB-NG.cmake or something like that?
Can @negril @parona-source or @sgoth offer a pull request that addresses their request?

[sgoth]

I can try later today yes.

I think actually it's two things for me:

• building minizip-ng with zlib-ng works fine but consuming the result via cmake (transitive dependency zlib-ng not found) due to this issue

• find_package for zlib-ng before zlib unconditionally breaks package managers like vcpkg (conan probably too) when the system contains zlib-ng but the modeled dependency should use zlib
  The managers usually set up an environment where expected dependencies have paths configured to other dependencies from the manager.
  So for me vcpkg sets up everything so minizip-ng would find the correct zlib - but minizip-ngs cmake just finds system wide zlib-ng and doesn't care.
  Should probably be a separate issue but i'd suggest adding an option so users can explicitly decide if they want a zlib or zlib-ng dependency.