Split `OptionalPathSetting` from `PathSetting`

Rather than doing `allowEmpty` as boolean, have separate types and use
`std::optional`. This makes it harder to forget the possibility of an
empty path.

The `build-hook` setting was categorized as a `PathSetting`, but
actually it was split into arguments. No good! Now, it is
`Setting<Strings>` which actually reflects what it means and how it is
used.

Because of the subtyping, we now also have support for
`Setting<std::optional<String>>` in general. I imagine this can be used
to clean up many more settings also.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/libstore/build/hook-instance.cc b/src/libstore/build/hook-instance.cc
index 075ad554f..337c60bd4 100644
--- a/src/libstore/build/hook-instance.cc
+++ b/src/libstore/build/hook-instance.cc
@@ -5,14 +5,14 @@ namespace nix {
 
 HookInstance::HookInstance()
 {
-    debug("starting build hook '%s'", settings.buildHook);
+    debug("starting build hook '%s'", concatStringsSep(" ", settings.buildHook.get()));
 
-    auto buildHookArgs = tokenizeString<std::list<std::string>>(settings.buildHook.get());
+    auto buildHookArgs = settings.buildHook.get();
 
     if (buildHookArgs.empty())
         throw Error("'build-hook' setting is empty");
 
-    auto buildHook = buildHookArgs.front();
+    auto buildHook = canonPath(buildHookArgs.front());
     buildHookArgs.pop_front();
 
     Strings args;