Make RemoteStore::ConnectionHandle part of class and expose

Will need to do subclass-specific implementations in the next commit.
This isn't because there will be multiple variations of the daemon
protocol (whew!) but because different clients pick and choose different
parts to use.

src/libstore/remote-store-connection.hh

@@ -1,5 +1,6 @@
 #include "remote-store.hh"
 #include "worker-protocol.hh"
+#include "pool.hh"
 
 namespace nix {
 
@@ -94,4 +95,34 @@ struct RemoteStore::Connection
     std::exception_ptr processStderr(Sink * sink = 0, Source * source = 0, bool flush = true);
 };
 
+/**
+ * A wrapper around Pool<RemoteStore::Connection>::Handle that marks
+ * the connection as bad (causing it to be closed) if a non-daemon
+ * exception is thrown before the handle is closed. Such an exception
+ * causes a deviation from the expected protocol and therefore a
+ * desynchronization between the client and daemon.
+ */
+struct RemoteStore::ConnectionHandle
+{
+    Pool<RemoteStore::Connection>::Handle handle;
+    bool daemonException = false;
+
+    ConnectionHandle(Pool<RemoteStore::Connection>::Handle && handle)
+        : handle(std::move(handle))
+    { }
+
+    ConnectionHandle(ConnectionHandle && h)
+        : handle(std::move(h.handle))
+    { }
+
+    ~ConnectionHandle();
+
+    RemoteStore::Connection & operator * () { return *handle; }
+    RemoteStore::Connection * operator -> () { return &*handle; }
+
+    void processStderr(Sink * sink = 0, Source * source = 0, bool flush = true);
+
+    void withFramedSink(std::function<void(Sink & sink)> fun);
+};
+
 }

src/libstore/remote-store.cc

@@ -159,49 +159,25 @@ void RemoteStore::setOptions(Connection & conn)
 }
 
 
-/* A wrapper around Pool<RemoteStore::Connection>::Handle that marks
-   the connection as bad (causing it to be closed) if a non-daemon
-   exception is thrown before the handle is closed. Such an exception
-   causes a deviation from the expected protocol and therefore a
-   desynchronization between the client and daemon. */
-struct ConnectionHandle
+RemoteStore::ConnectionHandle::~ConnectionHandle()
 {
-    Pool<RemoteStore::Connection>::Handle handle;
-    bool daemonException = false;
-
-    ConnectionHandle(Pool<RemoteStore::Connection>::Handle && handle)
-        : handle(std::move(handle))
-    { }
-
-    ConnectionHandle(ConnectionHandle && h)
-        : handle(std::move(h.handle))
-    { }
-
-    ~ConnectionHandle()
-    {
-        if (!daemonException && std::uncaught_exceptions()) {
-            handle.markBad();
-            debug("closing daemon connection because of an exception");
-        }
+    if (!daemonException && std::uncaught_exceptions()) {
+        handle.markBad();
+        debug("closing daemon connection because of an exception");
     }
+}
 
-    RemoteStore::Connection * operator -> () { return &*handle; }
-    RemoteStore::Connection & operator * () { return *handle; }
-
-    void processStderr(Sink * sink = 0, Source * source = 0, bool flush = true)
-    {
-        auto ex = handle->processStderr(sink, source, flush);
-        if (ex) {
-            daemonException = true;
-            std::rethrow_exception(ex);
-        }
+void RemoteStore::ConnectionHandle::processStderr(Sink * sink, Source * source, bool flush)
+{
+    auto ex = handle->processStderr(sink, source, flush);
+    if (ex) {
+        daemonException = true;
+        std::rethrow_exception(ex);
     }
-
-    void withFramedSink(std::function<void(Sink & sink)> fun);
-};
+}
 
 
-ConnectionHandle RemoteStore::getConnection()
+RemoteStore::ConnectionHandle RemoteStore::getConnection()
 {
     return ConnectionHandle(connections->get());
 }
@@ -1099,7 +1075,7 @@ std::exception_ptr RemoteStore::Connection::processStderr(Sink * sink, Source *
     return nullptr;
 }
 
-void ConnectionHandle::withFramedSink(std::function<void(Sink & sink)> fun)
+void RemoteStore::ConnectionHandle::withFramedSink(std::function<void(Sink & sink)> fun)
 {
     (*this)->to.flush();
 

src/libstore/remote-store.hh

@@ -17,7 +17,6 @@ class Pid;
 struct FdSink;
 struct FdSource;
 template<typename T> class Pool;
-struct ConnectionHandle;
 
 struct RemoteStoreConfig : virtual StoreConfig
 {
@@ -182,6 +181,8 @@ protected:
 
     void setOptions() override;
 
+    struct ConnectionHandle;
+
     ConnectionHandle getConnection();
 
     friend struct ConnectionHandle;
@@ -199,5 +200,4 @@ private:
         std::shared_ptr<Store> evalStore);
 };
 
-
 }