[Bronek]

Port the fixes from the Conan Center review of the libfn recipe (conan-io/conan-center-index#30871) to the in-repo conanfile.py, and tidy the README sections around packaging.

CMakeDeps links every component into the libfn::libfn aggregate. With fn_cxx26 as a component, any consumer linking libfn::libfn got LIBFN_CXX26 and, through the recipe's build module, C++26 without asking for either. A cxx26 option replaces the component: it selects the mode for the whole dependency graph, the profile's compiler.cppstd selects the standard, and libfn::fn_cxx26 becomes an alias of libfn::fn when the option is set.

Changes for Conan consumers:

• Select the C++26 mode with -o "libfn/*:cxx26=True" and -s compiler.cppstd=26; without the option, libfn::fn_cxx26 does not exist.
• Linking libfn::libfn no longer selects the mode.
• The package provides libfn::version, as the CMake package does.
• The recipe rejects compilers below the supported floors (GCC 12, Clang 19, Apple Clang 21, MSVC 2022), as the Conan Center recipe does with its own floors.

Other changes:

• The recipe packages the headers through the CMake install rules, so its contents follow the install list.
• test_package compiles a mode check against libfn::libfn, and no longer sets the C++ standard itself; it builds only if the package (or the Conan profile) supplies C++20.
• The Linux Conan lane resolves the recipe's cmake tool requirement to the image's CMake: ConanCenter has no Linux arm64 cmake binary, so the lane would otherwise build cmake from source on every run.
• README: Conan mode selection, which routes supply compile options and the C++ standard, and a merged versioning section.

Verified locally with gcc 16.2.1 and Conan 2.31.1: both Conan lanes pass; the mode check fails for a recipe that puts a fn_cxx26 component back and for one whose cxx26 option omits the define; the packaged headers match include/*.hpp. Through the installed CMake package and clang 22 (default C++17), test_package builds as C++20 and fails once the package's compile features are removed. The Windows lane is covered by CI only.

Assisted-by: Claude:claude-opus-5-5
Assisted-by: Codex:gpt-6.1-sol

[augmentcode]

🤖 Augment PR Summary

Summary: Makes Conan C++26 mode selection explicit and aligns packaging with CMake.

• Replaces the fn_cxx26 component with a default-off cxx26 option.
• Avoids enabling the mode merely by linking the aggregate libfn::libfn target.
• Validates C++20/C++26 requirements; the Conan profile selects the language standard.
• Defines LIBFN_CXX26 on libfn::fn and conditionally exposes libfn::fn_cxx26 as an alias.
• Adds libfn::version and aligns component dependencies and compiler options.
• Configures CMake with tests disabled and packages headers through its install rules.
• Removes installed CMake metadata so Conan-generated targets remain authoritative.
• Adds an aggregate-mode check and derives test selection from the dependency option.
• Updates Conan CI commands, Linux CMake resolution, packaging docs, and versioning guidance.

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[augmentcode]

Review completed. 1 suggestion posted.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud