Make the Store API more type-safe

Most functions now take a StorePath argument rather than a Path (which
is just an alias for std::string). The StorePath constructor ensures
that the path is syntactically correct (i.e. it looks like
<store-dir>/<base32-hash>-<name>). Similarly, functions like
buildPaths() now take a StorePathWithOutputs, rather than abusing Path
by adding a '!<outputs>' suffix.

Note that the StorePath type is implemented in Rust. This involves
some hackery to allow Rust values to be used directly in C++, via a
helper type whose destructor calls the Rust type's drop()
function. The main issue is the dynamic nature of C++ move semantics:
after we have moved a Rust value, we should not call the drop function
on the original value. So when we move a value, we set the original
value to bitwise zero, and the destructor only calls drop() if the
value is not bitwise zero. This should be sufficient for most types.

Also lots of minor cleanups to the C++ API to make it more modern
(e.g. using std::optional and std::string_view in some places).

1 files changed, 21 insertions, 16 deletions

diff --git a/src/libstore/export-import.cc b/src/libstore/export-import.cc
index ef3fea7c8..4692d1a7b 100644
--- a/src/libstore/export-import.cc
+++ b/src/libstore/export-import.cc
@@ -24,9 +24,9 @@ struct HashAndWriteSink : Sink
     }
 };
 
-void Store::exportPaths(const Paths & paths, Sink & sink)
+void Store::exportPaths(const StorePathSet & paths, Sink & sink)
 {
-    Paths sorted = topoSortPaths(PathSet(paths.begin(), paths.end()));
+    auto sorted = topoSortPaths(paths);
     std::reverse(sorted.begin(), sorted.end());
 
     std::string doneLabel("paths exported");
@@ -42,7 +42,7 @@ void Store::exportPaths(const Paths & paths, Sink & sink)
     sink << 0;
 }
 
-void Store::exportPath(const Path & path, Sink & sink)
+void Store::exportPath(const StorePath & path, Sink & sink)
 {
     auto info = queryPathInfo(path);
 
@@ -55,15 +55,21 @@ void Store::exportPath(const Path & path, Sink & sink)
        Don't complain if the stored hash is zero (unknown). */
     Hash hash = hashAndWriteSink.currentHash();
     if (hash != info->narHash && info->narHash != Hash(info->narHash.type))
-        throw Error(format("hash of path '%1%' has changed from '%2%' to '%3%'!") % path
-            % info->narHash.to_string() % hash.to_string());
-
-    hashAndWriteSink << exportMagic << path << info->references << info->deriver << 0;
+        throw Error("hash of path '%s' has changed from '%s' to '%s'!",
+            printStorePath(path), info->narHash.to_string(), hash.to_string());
+
+    hashAndWriteSink
+        << exportMagic
+        << printStorePath(path);
+    writeStorePaths(*this, hashAndWriteSink, info->references);
+    hashAndWriteSink
+        << (info->deriver ? printStorePath(*info->deriver) : "")
+        << 0;
 }
 
-Paths Store::importPaths(Source & source, std::shared_ptr<FSAccessor> accessor, CheckSigsFlag checkSigs)
+StorePaths Store::importPaths(Source & source, std::shared_ptr<FSAccessor> accessor, CheckSigsFlag checkSigs)
 {
-    Paths res;
+    StorePaths res;
     while (true) {
         auto n = readNum<uint64_t>(source);
         if (n == 0) break;
@@ -77,16 +83,15 @@ Paths Store::importPaths(Source & source, std::shared_ptr<FSAccessor> accessor,
         if (magic != exportMagic)
             throw Error("Nix archive cannot be imported; wrong format");
 
-        ValidPathInfo info;
-
-        info.path = readStorePath(*this, source);
+        ValidPathInfo info(parseStorePath(readString(source)));
 
         //Activity act(*logger, lvlInfo, format("importing path '%s'") % info.path);
 
-        info.references = readStorePaths<PathSet>(*this, source);
+        info.references = readStorePaths<StorePathSet>(*this, source);
 
-        info.deriver = readString(source);
-        if (info.deriver != "") assertStorePath(info.deriver);
+        auto deriver = readString(source);
+        if (deriver != "")
+            info.deriver = parseStorePath(deriver);
 
         info.narHash = hashString(htSHA256, *tee.source.data);
         info.narSize = tee.source.data->size();
@@ -97,7 +102,7 @@ Paths Store::importPaths(Source & source, std::shared_ptr<FSAccessor> accessor,
 
         addToStore(info, tee.source.data, NoRepair, checkSigs, accessor);
 
-        res.push_back(info.path);
+        res.push_back(info.path.clone());
     }
 
     return res;