Harmonise the Store::queryPathInfoUncached interface

This:
 - Consistently returns `nullptr` for a non-existent
   store path, instead of a mix of `nullptr` and
   throwing exceptions.

 - If a store returns "bad" store paths in response
   to a request (e.g. incorrect hash or name), don't
   cache this result. This removes some duplication
   of code at the cache-access layer of queryPathInfo()
   checking this, and ­allows us to provide more
   specific errors.

Part of #270.

Change-Id: I86612c6499b1a37ab872c712c2304d6a3ff19edb

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index f5eaa9f5f..bae5fad7b 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -899,7 +899,7 @@ std::shared_ptr<const ValidPathInfo> LocalStore::queryPathInfoInternal(State & s
     auto useQueryPathInfo(state.stmts->QueryPathInfo.use()(printStorePath(path)));
 
     if (!useQueryPathInfo.next())
-        return std::shared_ptr<ValidPathInfo>();
+        return nullptr;
 
     auto id = useQueryPathInfo.getInt(0);