Add a way to get all the outputs of a derivation with their label

Generalize `queryDerivationOutputNames` and `queryDerivationOutputs` by
adding a `queryDerivationOutputMap` that returns the map
`outputName=>outputPath`

(not that this is not equivalent to merging the results of
`queryDerivationOutputs` and `queryDerivationOutputNames` as sets don't
preserve the order, so we would end up with an incorrect mapping).

squash! Add a way to get all the outputs of a derivation with their label

Rename StorePathMap to OutputPathMap

src/libstore/build.cc

@@ -2750,8 +2750,8 @@ struct RestrictedStore : public LocalFSStore
     void queryReferrers(const StorePath & path, StorePathSet & referrers) override
     { }
 
-    StorePathSet queryDerivationOutputs(const StorePath & path) override
+    OutputPathMap queryDerivationOutputMap(const StorePath & path) override
-    { throw Error("queryDerivationOutputs"); }
+    { throw Error("queryDerivationOutputMap"); }
 
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override
     { throw Error("queryPathFromHashPart"); }

src/libstore/daemon.cc

@@ -347,6 +347,15 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         break;
     }
 
+    case wopQueryDerivationOutputMap: {
+        auto path = store->parseStorePath(readString(from));
+        logger->startWork();
+        OutputPathMap outputs = store->queryDerivationOutputMap(path);
+        logger->stopWork();
+        writeOutputPathMap(*store, to, outputs);
+        break;
+    }
+
     case wopQueryDeriver: {
         auto path = store->parseStorePath(readString(from));
         logger->startWork();

src/libstore/local-store.cc

@@ -774,17 +774,20 @@ StorePathSet LocalStore::queryValidDerivers(const StorePath & path)
 }
 
 
-StorePathSet LocalStore::queryDerivationOutputs(const StorePath & path)
+OutputPathMap LocalStore::queryDerivationOutputMap(const StorePath & path)
 {
-    return retrySQLite<StorePathSet>([&]() {
+    return retrySQLite<OutputPathMap>([&]() {
         auto state(_state.lock());
 
         auto useQueryDerivationOutputs(state->stmtQueryDerivationOutputs.use()
             (queryValidPathId(*state, path)));
 
-        StorePathSet outputs;
+        OutputPathMap outputs;
         while (useQueryDerivationOutputs.next())
-            outputs.insert(parseStorePath(useQueryDerivationOutputs.getStr(1)));
+            outputs.emplace(
+                useQueryDerivationOutputs.getStr(0),
+                parseStorePath(useQueryDerivationOutputs.getStr(1))
+            );
 
         return outputs;
     });

src/libstore/local-store.hh

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

src/libstore/path.hh

@@ -62,6 +62,7 @@ public:
 
 typedef std::set<StorePath> StorePathSet;
 typedef std::vector<StorePath> StorePaths;
+typedef std::map<string, StorePath> OutputPathMap;
 
 /* Extension of derivations in the Nix store. */
 const std::string drvExtension = ".drv";

src/libstore/remote-store.cc

@@ -38,6 +38,32 @@ void writeStorePaths(const Store & store, Sink & out, const StorePathSet & paths
         out << store.printStorePath(i);
 }
 
+std::map<string, StorePath> readOutputPathMap(const Store & store, Source & from)
+{
+    std::map<string, StorePath> pathMap;
+    auto rawInput = readStrings<Strings>(from);
+    auto curInput = rawInput.begin();
+    while (curInput != rawInput.end()) {
+        string thisKey = *curInput;
+        curInput = std::next(curInput);
+        if (curInput == rawInput.end()) {
+            throw Error("Got an odd number of elements from the daemon when trying to read a map… that's odd");
+        }
+        string thisValue = *curInput;
+        curInput = std::next(curInput);
+        pathMap.emplace(thisKey, store.parseStorePath(thisValue));
+    }
+    return pathMap;
+}
+
+void writeOutputPathMap(const Store & store, Sink & out, const std::map<string, StorePath> & pathMap)
+{
+    out << 2*pathMap.size();
+    for (auto & i : pathMap) {
+        out << i.first;
+        out << store.printStorePath(i.second);
+    }
+}
 
 /* TODO: Separate these store impls into different files, give them better names */
 RemoteStore::RemoteStore(const Params & params)
@@ -412,12 +438,24 @@ StorePathSet RemoteStore::queryValidDerivers(const StorePath & path)
 StorePathSet RemoteStore::queryDerivationOutputs(const StorePath & path)
 {
     auto conn(getConnection());
+    if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 0x16) {
+        return Store::queryDerivationOutputs(path);
+    }
     conn->to << wopQueryDerivationOutputs << printStorePath(path);
     conn.processStderr();
     return readStorePaths<StorePathSet>(*this, conn->from);
 }
 
 
+OutputPathMap RemoteStore::queryDerivationOutputMap(const StorePath & path)
+{
+    auto conn(getConnection());
+    conn->to << wopQueryDerivationOutputMap << printStorePath(path);
+    conn.processStderr();
+    return readOutputPathMap(*this, conn->from);
+
+}
+
 std::optional<StorePath> RemoteStore::queryPathFromHashPart(const std::string & hashPart)
 {
     auto conn(getConnection());

src/libstore/remote-store.hh

@@ -51,6 +51,7 @@ public:
 
     StorePathSet queryDerivationOutputs(const StorePath & path) override;
 
+    OutputPathMap 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

@@ -242,6 +242,16 @@ bool Store::PathInfoCacheValue::isKnownNow()
     return std::chrono::steady_clock::now() < time_point + ttl;
 }
 
+StorePathSet Store::queryDerivationOutputs(const StorePath & path)
+{
+    auto outputMap = this->queryDerivationOutputMap(path);
+    StorePathSet outputPaths;
+    for (auto & i: outputMap) {
+        outputPaths.emplace(std::move(i.second));
+    }
+    return outputPaths;
+}
+
 bool Store::isValidPath(const StorePath & storePath)
 {
     std::string hashPart(storePath.hashPart());

src/libstore/store-api.hh

@@ -418,8 +418,11 @@ public:
     virtual StorePathSet queryValidDerivers(const StorePath & path) { return {}; };
 
     /* Query the outputs of the derivation denoted by `path'. */
-    virtual StorePathSet queryDerivationOutputs(const StorePath & path)
+    virtual StorePathSet queryDerivationOutputs(const StorePath & path);
-    { unsupported("queryDerivationOutputs"); }
+
+    /* Query the mapping outputName=>outputPath for the given derivation */
+    virtual OutputPathMap queryDerivationOutputMap(const StorePath & path)
+    { unsupported("queryDerivationOutputMap"); }
 
     /* Query the full store path given the hash part of a valid store
        path, or empty if the path doesn't exist. */

src/libstore/worker-protocol.hh

@@ -6,7 +6,7 @@ namespace nix {
 #define WORKER_MAGIC_1 0x6e697863
 #define WORKER_MAGIC_2 0x6478696f
 
-#define PROTOCOL_VERSION 0x115
+#define PROTOCOL_VERSION 0x116
 #define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
 #define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
 
@@ -30,7 +30,7 @@ typedef enum {
     wopSetOptions = 19,
     wopCollectGarbage = 20,
     wopQuerySubstitutablePathInfo = 21,
-    wopQueryDerivationOutputs = 22,
+    wopQueryDerivationOutputs = 22, // obsolete
     wopQueryAllValidPaths = 23,
     wopQueryFailedPaths = 24,
     wopClearFailedPaths = 25,
@@ -49,6 +49,7 @@ typedef enum {
     wopNarFromPath = 38,
     wopAddToStoreNar = 39,
     wopQueryMissing = 40,
+    wopQueryDerivationOutputMap = 41,
 } WorkerOp;
 
 
@@ -69,5 +70,6 @@ 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);
 
 }