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, 3 insertions, 3 deletions

diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 93b1afabd..966dd3fe0 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -309,14 +309,14 @@ std::shared_ptr<const ValidPathInfo> RemoteStore::queryPathInfoUncached(const St
     try {
         conn.processStderr();
     } catch (Error & e) {
-        // Ugly backwards compatibility hack.
+        // Ugly backwards compatibility hack. TODO(fj#325): remove.
         if (e.msg().find("is not valid") != std::string::npos)
-            throw InvalidPath(std::move(e.info()));
+            return nullptr;
         throw;
     }
     if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 17) {
         bool valid; conn->from >> valid;
-        if (!valid) throw InvalidPath("path '%s' is not valid", printStorePath(path));
+        if (!valid) return nullptr;
     }
     return std::make_shared<ValidPathInfo>(
         StorePath{path},