queryDerivationOutputMap no longer assumes all outputs have a mapping

This assumption is broken by CA derivations. Making a PR now to do the
breaking daemon change as soon as possible (if it is already too late,
we can bump protocol intead).

src/libstore/build.cc

@@ -2756,8 +2756,12 @@ struct RestrictedStore : public LocalFSStore
     void queryReferrers(const StorePath & path, StorePathSet & referrers) override
     { }
 
-    OutputPathMap queryDerivationOutputMap(const StorePath & path) override
-    { throw Error("queryDerivationOutputMap"); }
+    std::map<std::string, std::optional<StorePath>> queryDerivationOutputMap(const StorePath & path) override
+    {
+        if (!goal.isAllowed(path))
+            throw InvalidPath("cannot query output map for unknown path '%s' in recursive Nix", printStorePath(path));
+        return next->queryDerivationOutputMap(path);
+    }
 
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override
     { throw Error("queryPathFromHashPart"); }
@@ -4918,7 +4922,7 @@ void Worker::waitForInput()
         std::vector<unsigned char> buffer(4096);
         for (auto & k : fds2) {
             if (pollStatus.at(fdToPollStatus.at(k)).revents) {
-                ssize_t rd = read(k, buffer.data(), buffer.size());
+                ssize_t rd = ::read(k, buffer.data(), buffer.size());
                 // FIXME: is there a cleaner way to handle pt close
                 // than EIO? Is this even standard?
                 if (rd == 0 || (rd == -1 && errno == EIO)) {

src/libstore/daemon.cc

@@ -325,9 +325,9 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
     case wopQueryDerivationOutputMap: {
         auto path = store->parseStorePath(readString(from));
         logger->startWork();
-        OutputPathMap outputs = store->queryDerivationOutputMap(path);
+        auto outputs = store->queryDerivationOutputMap(path);
         logger->stopWork();
-        writeOutputPathMap(*store, to, outputs);
+        write(*store, to, outputs);
         break;
     }
 

src/libstore/local-store.cc

@@ -774,17 +774,21 @@ StorePathSet LocalStore::queryValidDerivers(const StorePath & path)
 }
 
 
-OutputPathMap LocalStore::queryDerivationOutputMap(const StorePath & path)
+std::map<std::string, std::optional<StorePath>> LocalStore::queryDerivationOutputMap(const StorePath & path)
 {
-    return retrySQLite<OutputPathMap>([&]() {
+    std::map<std::string, std::optional<StorePath>> outputs;
+    BasicDerivation drv = readDerivation(path);
+    for (auto & [outName, _] : drv.outputs) {
+        outputs.insert_or_assign(outName, std::nullopt);
+    }
+    return retrySQLite<std::map<std::string, std::optional<StorePath>>>([&]() {
         auto state(_state.lock());
 
         auto useQueryDerivationOutputs(state->stmtQueryDerivationOutputs.use()
             (queryValidPathId(*state, path)));
 
-        OutputPathMap outputs;
         while (useQueryDerivationOutputs.next())
-            outputs.emplace(
+            outputs.insert_or_assign(
                 useQueryDerivationOutputs.getStr(0),
                 parseStorePath(useQueryDerivationOutputs.getStr(1))
             );

src/libstore/local-store.hh

@@ -133,7 +133,7 @@ public:
 
     StorePathSet queryValidDerivers(const StorePath & path) override;
 
-    OutputPathMap queryDerivationOutputMap(const StorePath & path) override;
+    std::map<std::string, std::optional<StorePath>> queryDerivationOutputMap(const StorePath & path) override;
 
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override;
 

src/libstore/remote-store.cc

@@ -39,30 +39,21 @@ void writeStorePaths(const Store & store, Sink & out, const StorePathSet & paths
         out << store.printStorePath(i);
 }
 
-std::map<string, StorePath> readOutputPathMap(const Store & store, Source & from)
+
+StorePath read(const Store & store, Source & from, Proxy<StorePath> _)
 {
-    std::map<string, StorePath> pathMap;
-    auto rawInput = readStrings<Strings>(from);
-    if (rawInput.size() % 2)
-        throw Error("got an odd number of elements from the daemon when trying to read a output path map");
-    auto curInput = rawInput.begin();
-    while (curInput != rawInput.end()) {
-        auto thisKey = *curInput++;
-        auto thisValue = *curInput++;
-        pathMap.emplace(thisKey, store.parseStorePath(thisValue));
-    }
-    return pathMap;
+	auto path = readString(from);
+	return store.parseStorePath(path);
 }
 
-void writeOutputPathMap(const Store & store, Sink & out, const std::map<string, StorePath> & pathMap)
+
+void write(const Store & store, Sink & out, const StorePath & storePath)
 {
-    out << 2*pathMap.size();
-    for (auto & i : pathMap) {
-        out << i.first;
-        out << store.printStorePath(i.second);
-    }
+	auto path = store.printStorePath(storePath);
+	out << path;
 }
 
+
 /* TODO: Separate these store impls into different files, give them better names */
 RemoteStore::RemoteStore(const Params & params)
     : Store(params)
@@ -445,12 +436,12 @@ StorePathSet RemoteStore::queryDerivationOutputs(const StorePath & path)
 }
 
 
-OutputPathMap RemoteStore::queryDerivationOutputMap(const StorePath & path)
+std::map<std::string, std::optional<StorePath>> RemoteStore::queryDerivationOutputMap(const StorePath & path)
 {
     auto conn(getConnection());
     conn->to << wopQueryDerivationOutputMap << printStorePath(path);
     conn.processStderr();
-    return readOutputPathMap(*this, conn->from);
+    return read(*this, conn->from, Proxy<std::map<std::string, std::optional<StorePath>>> {});
 
 }
 

src/libstore/remote-store.hh

@@ -51,7 +51,7 @@ public:
 
     StorePathSet queryDerivationOutputs(const StorePath & path) override;
 
-    OutputPathMap queryDerivationOutputMap(const StorePath & path) override;
+    std::map<std::string, std::optional<StorePath>> queryDerivationOutputMap(const StorePath & path) override;
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override;
 
     StorePathSet querySubstitutablePaths(const StorePathSet & paths) override;

src/libstore/store-api.cc

@@ -330,9 +330,20 @@ bool Store::PathInfoCacheValue::isKnownNow()
     return std::chrono::steady_clock::now() < time_point + ttl;
 }
 
+OutputPathMap Store::queryDerivationOutputMapAssumeTotal(const StorePath & path) {
+	auto resp = queryDerivationOutputMap(path);
+	OutputPathMap result;
+	for (auto & [outName, optOutPath] : resp) {
+		if (!optOutPath)
+			throw Error("output '%s' has no store path mapped to it", outName);
+		result.insert_or_assign(outName, *optOutPath);
+	}
+	return result;
+}
+
 StorePathSet Store::queryDerivationOutputs(const StorePath & path)
 {
-    auto outputMap = this->queryDerivationOutputMap(path);
+    auto outputMap = this->queryDerivationOutputMapAssumeTotal(path);
     StorePathSet outputPaths;
     for (auto & i: outputMap) {
         outputPaths.emplace(std::move(i.second));

src/libstore/store-api.hh

@@ -423,10 +423,16 @@ public:
     /* Query the outputs of the derivation denoted by `path'. */
     virtual StorePathSet queryDerivationOutputs(const StorePath & path);
 
-    /* Query the mapping outputName=>outputPath for the given derivation */
-    virtual OutputPathMap queryDerivationOutputMap(const StorePath & path)
+    /* Query the mapping outputName => outputPath for the given derivation. All
+       outputs are mentioned so ones mising the mapping are mapped to
+       `std::nullopt`.  */
+    virtual std::map<std::string, std::optional<StorePath>> queryDerivationOutputMap(const StorePath & path)
     { unsupported("queryDerivationOutputMap"); }
 
+    /* Query the mapping outputName=>outputPath for the given derivation.
+       Assume every output has a mapping and throw an exception otherwise. */
+    OutputPathMap queryDerivationOutputMapAssumeTotal(const StorePath & path);
+
     /* Query the full store path given the hash part of a valid store
        path, or empty if the path doesn't exist. */
     virtual std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) = 0;

src/libstore/worker-protocol.hh

@@ -70,6 +70,56 @@ template<class T> T readStorePaths(const Store & store, Source & from);
 
 void writeStorePaths(const Store & store, Sink & out, const StorePathSet & paths);
 
-void writeOutputPathMap(const Store & store, Sink & out, const OutputPathMap & paths);
+/* To guide overloading */
+template<typename T>
+struct Proxy {};
+
+template<typename T>
+std::map<std::string, T> read(const Store & store, Source & from, Proxy<std::map<std::string, T>> _)
+{
+    std::map<string, T> resMap;
+    auto size = (size_t)readInt(from);
+    while (size--) {
+        auto thisKey = readString(from);
+        resMap.insert_or_assign(std::move(thisKey), read(store, from, Proxy<T> {}));
+    }
+    return resMap;
+}
+
+template<typename T>
+void write(const Store & store, Sink & out, const std::map<string, T> & resMap)
+{
+    out << resMap.size();
+    for (auto & i : resMap) {
+        out << i.first;
+        write(store, out, i.second);
+    }
+}
+
+template<typename T>
+std::optional<T> read(const Store & store, Source & from, Proxy<std::optional<T>> _)
+{
+    auto tag = readNum<uint8_t>(from);
+    switch (tag) {
+    case 0:
+        return std::nullopt;
+    case 1:
+        return read(store, from, Proxy<T> {});
+    default:
+        throw Error("got an invalid tag bit for std::optional: %#04x", tag);
+    }
+}
+
+template<typename T>
+void write(const Store & store, Sink & out, const std::optional<T> & optVal)
+{
+    out << (optVal ? 1 : 0);
+    if (optVal)
+        write(store, out, *optVal);
+}
+
+StorePath read(const Store & store, Source & from, Proxy<StorePath> _);
+
+void write(const Store & store, Sink & out, const StorePath & storePath);
 
 }

src/nix-env/nix-env.cc

@@ -381,7 +381,7 @@ static void queryInstSources(EvalState & state,
 
                 if (path.isDerivation()) {
                     elem.setDrvPath(state.store->printStorePath(path));
-                    auto outputs = state.store->queryDerivationOutputMap(path);
+                    auto outputs = state.store->queryDerivationOutputMapAssumeTotal(path);
                     elem.setOutPath(state.store->printStorePath(outputs.at("out")));
                     if (name.size() >= drvExtension.size() &&
                         string(name, name.size() - drvExtension.size()) == drvExtension)