Your explanations are very helpful, thank you, and your links made
me realize that devel version of the manual has lots of
information that I could not find in the stable version of the
manual.
During the build, search-paths and native-search-paths are used
to set up environment variables. If you use --keep-failed and
interrupt a
build you'l find them in
/tmp/guix-build-…/environment-variables.
So search-paths and native-search-paths are set before the build
and unset after the build so they are unavailable during run-time?
Or are native-search-paths only available at build-time and
search-paths available at both build-time and run-time?
Are the search-paths and native-search-paths absolute path values
found by automatically searching the directories in all of the
inputs or native inputs, looking for files or directories that
match a pattern? So they are a way to map relative paths into
absolute paths to the dependency packages?
For others, the required search paths can be embedded in a
wrapper, which defines environment variables before calling the
actual program.
So if a package needs run-time environment variables, then a
package should use wrap-program to attach them to a command? These
are not found automatically by searching the inputs, they must be
manually defined using explicit input paths?
For propagation, dependencies are found in the environment. It's
less "pure" than the other ways, so we try to avoid resorting to
that.
Unfortunately some programming languages don't really leave us a
choice (like python…).
So python packages are not using an environment variable, such as
PYTHONPATH, to find dependencies? How are they placed together
into an environment so they can find each other?