[bug] setting 2nd level settings forces specifying 1st level setting even if it exists.

[fulara]

Following great comment from SSE4: #6157 (comment) Which actually saved my day as I thought that I am doomed and unable to migrate from cppstd tocompiler.cppstd I went to test it.

However I was met with a slightly off behavior, upon invoking:
conan create . lib1/1.0@ -s compiler.cppstd=14 -s lib0:compiler.cppstd=17
I am getting an error:

ERROR: /home/fulara/.conan/data/lib0/1.0/_/_/export/conanfile.py: compiler not defined for compiler.cppstd
Please define compiler value first too

Even though the compiler value already exists, see full output:

[fulara@localhost lib1]$ conan create . lib1/1.0@ -s compiler.cppstd=14  -s lib0:compiler.cppstd=17
[HOOK - attribute_checker.py] pre_export(): WARN: Conanfile doesn't have 'url'. It is recommended to add it as attribute
[HOOK - attribute_checker.py] pre_export(): WARN: Conanfile doesn't have 'license'. It is recommended to add it as attribute
[HOOK - attribute_checker.py] pre_export(): WARN: Conanfile doesn't have 'description'. It is recommended to add it as attribute
Exporting package recipe
lib1/1.0 exports_sources: Copied 1 '.h' file: h.h
lib1/1.0 exports_sources: Copied 1 '.cpp' file: h.cpp
lib1/1.0 exports_sources: Copied 1 '.txt' file: CMakeLists.txt
lib1/1.0: The stored package has not changed
lib1/1.0: Exported revision: 110ee250f4990ce2f2a348d460cc0b60
Configuration:
[settings]
arch=x86_64
arch_build=x86_64
build_type=Release
compiler=gcc
compiler.cppstd=14
compiler.libcxx=libstdc++
compiler.version=8
os=Linux
os_build=Linux
lib0:compiler.cppstd=17
[options]
[build_requires]
[env]

ERROR: /home/fulara/.conan/data/lib0/1.0/_/_/export/conanfile.py: compiler not defined for compiler.cppstd
Please define compiler value first too

I am forced to do this nasty command:
conan create . lib1/1.0@ -s compiler.cppstd=14 -s lib0:compiler=$(conan profile get settings.compiler default) -s lib0:compiler.cppstd=17

I've chatted with SSE4 and he said:

(...) no, might be some limitation in code, I'd suggest you to create an issue

[AbrilRBS]

Closing following #6702 (comment)