libutil: make Activity a real, move-only class

activities are scopes, and there's no reason scopes should not be able
to move around. this also means we can *create* them elsewhere without
also having to box them in some way, making parent relationships clear

Change-Id: I5df036e12ebd8270feb4dca1f23b6bee1f08e906

lix/libstore/binary-cache-store.cc

@@ -469,7 +469,7 @@ try {
         actQueryPathInfo,
         fmt("querying info about '%s' on '%s'", storePathS, uri),
         Logger::Fields{storePathS, uri},
-        context ? context->id : 0
+        context
     );
 
     auto narInfoFile = narInfoFileFor(storePath);

lix/libstore/filetransfer.cc

@@ -142,7 +142,7 @@ struct curlFileTransfer : public FileTransfer
         TransferItem(
             const std::string & uri,
             FileTransferOptions && options,
-            ActivityId parentAct,
+            const Activity * parentAct,
             std::optional<std::string_view> uploadData,
             bool noBody,
             curl_off_t writtenToSink,
@@ -904,7 +904,7 @@ struct curlFileTransfer : public FileTransfer
         FileTransferOptions options;
         std::optional<std::string> data;
         bool noBody;
-        ActivityId parentAct;
+        const Activity * parentAct;
 
         std::shared_ptr<TransferItem> transfer;
         FileTransferResult metadata;
@@ -929,7 +929,7 @@ struct curlFileTransfer : public FileTransfer
             , options(options)
             , data(std::move(data))
             , noBody(noBody)
-            , parentAct(context ? context->id : 0)
+            , parentAct(context)
             , backoff(backoffTimeouts(
                   fileTransferSettings.tries,
                   std::chrono::seconds(fileTransferSettings.maxConnectTimeout.get()),

lix/libstore/store-api.cc

@@ -1040,7 +1040,7 @@ try {
         actCopyPath,
         makeCopyPathMessage(srcUri, dstUri, storePathS),
         {storePathS, srcUri, dstUri},
-        context ? context->id : 0
+        context
     );
 
     auto info = TRY_AWAIT(srcStore.queryPathInfo(storePath, &act));

lix/libutil/logging.cc

@@ -120,11 +120,18 @@ Logger * makeSimpleLogger(bool printBuildLogs)
 
 std::atomic<uint64_t> nextId{0};
 
-Activity::Activity(Logger & logger, Verbosity lvl, ActivityType type,
-    const std::string & s, const Logger::Fields & fields, ActivityId parent)
-    : logger(logger), id(nextId++ + (((uint64_t) getpid()) << 32))
+Activity::Activity(
+    Logger & logger,
+    Verbosity lvl,
+    ActivityType type,
+    const std::string & s,
+    const Logger::Fields & fields,
+    const Activity * parent
+)
+    : logger(&logger)
+    , id(nextId++ + (((uint64_t) getpid()) << 32))
 {
-    logger.startActivity(id, lvl, type, s, fields, parent);
+    logger.startActivity(id, lvl, type, s, fields, parent ? parent->id : 0);
 }
 
 void to_json(JSON & json, std::shared_ptr<Pos> pos)
@@ -279,10 +286,18 @@ bool handleJSONLogMessage(JSON & json,
         if (action == "start") {
             auto type = (ActivityType) json["type"];
             if (trusted || type == actFileTransfer)
-                activities.emplace(std::piecewise_construct,
+                activities.emplace(
+                    std::piecewise_construct,
                     std::forward_as_tuple(json["id"]),
-                    std::forward_as_tuple(*logger, (Verbosity) json["level"], type,
-                        json["text"], getFields(json["fields"]), act.id));
+                    std::forward_as_tuple(
+                        *logger,
+                        (Verbosity) json["level"],
+                        type,
+                        json["text"],
+                        getFields(json["fields"]),
+                        &act
+                    )
+                );
         }
 
         else if (action == "stop")
@@ -324,8 +339,11 @@ bool handleJSONLogMessage(const std::string & msg,
 
 Activity::~Activity()
 {
+    if (!logger) {
+        return;
+    }
     try {
-        logger.stopActivity(id);
+        logger->stopActivity(id);
     } catch (...) {
         ignoreExceptionInDestructor();
     }

lix/libutil/logging.hh

@@ -173,31 +173,51 @@ struct nop
 
 struct Activity
 {
-    Logger & logger;
+private:
+    Logger * logger;
 
-    const ActivityId id;
+    ActivityId id;
 
+public:
     Activity(
         Logger & logger,
         Verbosity lvl,
         ActivityType type,
         const std::string & s = "",
         const Logger::Fields & fields = {},
-        ActivityId parent = 0
+        const Activity * parent = nullptr
     );
 
     Activity(
         Logger & logger,
         ActivityType type,
         const Logger::Fields & fields = {},
-        ActivityId parent = 0
+        const Activity * parent = nullptr
     )
         : Activity(logger, lvlError, type, "", fields, parent) {};
 
+    Activity(Activity && other) : logger(nullptr), id(0)
+    {
+        swap(other);
+    }
+
+    Activity & operator=(Activity && other)
+    {
+        Activity(std::move(other)).swap(*this);
+        return *this;
+    }
+
     Activity(const Activity & act) = delete;
+    Activity & operator=(const Activity & act) = delete;
 
     ~Activity();
 
+    void swap(Activity & other)
+    {
+        std::swap(logger, other.logger);
+        std::swap(id, other.id);
+    }
+
     void progress(uint64_t done = 0, uint64_t expected = 0, uint64_t running = 0, uint64_t failed = 0) const
     { result(resProgress, done, expected, running, failed); }
 
@@ -214,7 +234,7 @@ struct Activity
 
     void result(ResultType type, const Logger::Fields & fields) const
     {
-        logger.result(id, type, fields);
+        logger->result(id, type, fields);
     }
 
     friend class Logger;