adjust_config fails to build.

[pcanal]

In my configuration adjust_config fails to compile:

72/75] Scanning /home/pcanal/phlex_working/code/phlex/test/adjust_config.cpp for CXX dependencies
FAILED: [code=1] test/CMakeFiles/adjust_config.dir/adjust_config.cpp.o.ddi 
/home/pcanal/phlex_working/code/spack/opt/spack/linux-almalinux9-zen2/llvm-15.0.7/gcc-15.2.0-y4gwyaa7hif3hu2vttr4umq2vk657uw4/bin/g++ -DBOOST_CONTAINER_DYN_LINK -DBOOST_CONTAINER_NO_LIB -DBOOST_JSON_DYN_LINK -DBOOST_JSON_NO_LIB -I/home/pcanal/phlex_working/build/2025-12 -I/home/pcanal/phlex_working/code/phlex -isystem /home/pcanal/phlex_working/code/spack/opt/spack/linux-almalinux9-zen2/gcc-15.2.0/catch2-3.8.0-szsrxjdkgwmljpwg6t23udku6xsu3wjy/include -isystem /home/pcanal/phlex_working/code/spack/opt/spack/linux-almalinux9-zen2/gcc-15.2.0/boost-1.88.0-jo5efrhxwue76ysfbjsn3zrk4or6z4sk/include -g -std=c++20   -UNDEBUG -Wall -Werror -Wunused -Wunused-parameter -pedantic -Wno-array-bounds -Wno-stringop-overflow -E -x c++ /home/pcanal/phlex_working/code/phlex/test/adjust_config.cpp -MT test/CMakeFiles/adjust_config.dir/adjust_config.cpp.o.ddi -MD -MF test/CMakeFiles/adjust_config.dir/adjust_config.cpp.o.ddi.d -fmodules-ts -fdeps-file=test/CMakeFiles/adjust_config.dir/adjust_config.cpp.o.ddi -fdeps-target=test/CMakeFiles/adjust_config.dir/adjust_config.cpp.o -fdeps-format=p1689r5 -o test/CMakeFiles/adjust_config.dir/adjust_config.cpp.o.ddi.i
In file included from /home/pcanal/phlex_working/code/phlex/phlex/model/product_specification.hpp:5,
                 from /home/pcanal/phlex_working/code/phlex/phlex/core/product_query.hpp:4,
                 from /home/pcanal/phlex_working/code/phlex/phlex/configuration.hpp:5,
                 from /home/pcanal/phlex_working/code/phlex/phlex/driver.hpp:6,
                 from /home/pcanal/phlex_working/code/phlex/phlex/app/load_module.hpp:5,
                 from /home/pcanal/phlex_working/code/phlex/test/adjust_config.cpp:1:
/home/pcanal/phlex_working/code/phlex/phlex/model/type_id.hpp:7:10: fatal error: fmt/format.h: No such file or directory
    7 | #include "fmt/format.h"
      |          ^~~~~~~~~~~~~~
compilation terminated.
ninja: build stopped: cannot make progress due to previous errors.

The problem is that adjust_config.cpp uses phlex/model/type_id.hpp which uses fmt/format.h, however the dependency on fmt::fmt is indirectly private.

adjust_config depends on run_phlex which privately depends on phlex_core.

Thus there are many ways to solve this problem (all tested to lead to successful compilation ):

1. Make adjust_config depend on fmt::fmt explicitly (but technically this test would then need to be update each time phlex_core or phlex_model uses new external dependencies.
2. Make adjust_config depends on phlex_core in addition to run_phlex
3. Make run_phlex depends publicly on phlex_core

I guess the best option is (2). @knoepfel what is your opinion?

[pcanal]

run_phlex contains load_modules.hpp that includes:

#include "phlex/core/fwd.hpp"
#include "phlex/driver.hpp"
#include "boost/json.hpp"

So the best semantic solution is for run_phlex to publicly depend on phlex::core, Boost::json and the future library containing phlex/driver.hpp