Make `Buildable` a `std::variant`

I think this better captures the intent of what's going on: we either
have an opaque store path, or a drv path with some outputs.

Having this structure will also help us support CA derivations: we'll
have to allow the outpath paths to be optional, so the structure we gain
now makes up for the structure we loose then.

1 files changed, 8 insertions, 5 deletions

diff --git a/src/nix/log.cc b/src/nix/log.cc
index 7e10d373a..33380dcf5 100644
--- a/src/nix/log.cc
+++ b/src/nix/log.cc
@@ -45,11 +45,14 @@ struct CmdLog : InstallableCommand
 
         RunPager pager;
         for (auto & sub : subs) {
-            auto log = b.drvPath ? sub->getBuildLog(*b.drvPath) : nullptr;
-            for (auto & output : b.outputs) {
-                if (log) break;
-                log = sub->getBuildLog(output.second);
-            }
+            auto log = std::visit(overloaded {
+                [&](BuildableOpaque bo) {
+                    return sub->getBuildLog(bo.path);
+                },
+                [&](BuildableFromDrv bfd) {
+                    return sub->getBuildLog(bfd.drvPath);
+                },
+            }, b);
             if (!log) continue;
             stopProgressBar();
             printInfo("got build log for '%s' from '%s'", installable->what(), sub->getUri());