Include what you use

There are a couple of things to call out here:

1. I have done this naively. We may want consumers of this API to only have to include <transport/transport.h> to get all/some subset of the <transport/*.h> headers. We can add a pragma to mark those as exported, that consumers of the API and ourselves will understand if they also run clang-tidy or IWYU.
2. On MacOS at least, IncludeCleaner suggests some private MacOS headers that contain the actual implementations rather than the more canonical UNIX headers. E.g timeval should come from sys/time.h not <sys/types/_timeval.h>. IWYU allows a mapping file to correct these, but clang-tidy's version doesn't seem to. I have marked them NOLINT for now.

.clang-tidy

@@ -1,6 +1,7 @@
 Checks: '
           -*,
           clang-analyzer-*,
+          misc-include-cleaner,
           misc-misplaced-const,
           performance-*,
           readability-avoid-const-params-in-decls,

src/transport.cpp

@@ -4,6 +4,9 @@
   #include <transport_picoquic.h>
 #endif
 #include <cantina/logger.h>
+#include <memory>
+#include <ostream>
+#include <stdexcept>
 
 namespace qtransport {
 

src/transport_picoquic.cpp

@@ -1,25 +1,47 @@
 #include "transport_picoquic.h"
 
+// PicoQuic.
+#include <picoquic.h>
 #include <picoquic_internal.h>
+#include <picoquic_packet_loop.h>
 #include <autoqlog.h>
 #include <picoquic_utils.h>
-
+#include <picoquic_config.h>
+#include <picosocks.h>
+
+// Transport.
+#include "transport/transport.h"
+#include "transport/transport_metrics.h"
+#include "transport/safe_queue.h"
+#include "transport/stream_buffer.h"
+#include "transport/priority_queue.h"
+#include "transport/span.h"
+#include "transport/time_queue.h"
+#include <cantina/logger.h>
+#include <cantina/logger_macros.h>
+
+// System.
 #include <arpa/inet.h>
+#include <sys/socket.h>
 #include <cassert>
 #include <cstring>
 #include <ctime>
 #include <iostream>
 #include <thread>
-#include <unistd.h>
+#include <cstdint>
+#include <optional>
+#include <utility>
+#include <memory>
+#include <mutex>
+#include <vector>
+#include <string>
+#include <chrono>
+#include <sstream>
+#include <stdexcept>
 
-#include <arpa/inet.h>
-#include <sys/select.h>
-#include <netdb.h>
 #if defined(__linux__)
 #include <net/ethernet.h>
 #include <netpacket/packet.h>
-#elif defined(__APPLE__)
-#include <net/if_dl.h>
 #endif
 
 using namespace qtransport;
@@ -836,7 +858,7 @@ PicoQuicTransport::ConnectionContext& PicoQuicTransport::createConnContext(picoq
                             /*(const void*)(&((struct sockaddr_in*)addr)->sin_addr),*/
                             conn_ctx.peer_addr_text,
                             sizeof(conn_ctx.peer_addr_text));
-            conn_ctx.peer_port = ntohs(((struct sockaddr_in*)addr)->sin_port);
+            conn_ctx.peer_port = ntohs(((struct sockaddr_in*)addr)->sin_port); // NOLINT (include)
             break;
 
         case AF_INET6:

src/transport_udp.cpp

@@ -3,21 +3,40 @@
 #include <iostream>
 #include <thread>
 #include <unistd.h>
-
+#include <optional>
+#include <memory>
+#include <cstdint>
+#include <mutex>
+#include <utility>
+#include <vector>
+#include <chrono>
+#include <string>
+#include <sstream>
+#include <stdexcept>
+
+#include <netinet/in.h>
 #include <sys/socket.h>
+#include <sys/select.h> // IWYU pragma: keep
+#include <sys/time.h> // IWYU pragma: keep
 #include <arpa/inet.h>
 #include <netdb.h>
+#include <errno.h>
 
 #if defined(__linux__)
 #include <net/ethernet.h>
 #include <netpacket/packet.h>
-#elif defined(__APPLE__)
-
-#include <net/if_dl.h>
-
 #endif
 
 #include "transport_udp.h"
+#include "transport_udp_protocol.h"
+
+#include "transport/transport.h"
+#include "transport/time_queue.h"
+#include "transport/transport_metrics.h"
+#include "transport/uintvar.h"
+#include "transport/priority_queue.h"
+#include <cantina/logger.h>
+
 
 #if defined(PLATFORM_ESP)
 #include <lwip/netdb.h>
@@ -503,7 +522,7 @@ bool UDPTransport::send_data(ConnectionContext& conn, DataContext& data_ctx, con
  *  - loop reads data from fd_write_queue and writes it to the socket
  */
 void UDPTransport::fd_writer() {
-    timeval to;
+    timeval to; // NOLINT (include).
     to.tv_usec = 1000;
     to.tv_sec = 0;
 
@@ -614,7 +633,7 @@ void UDPTransport::fd_writer() {
             if (all_empty_count > 5) {
                 all_empty_count = 1;
                 to.tv_usec = 300;
-                select(0, NULL, NULL, NULL, &to);
+                select(0, NULL, NULL, NULL, &to); // NOLINT (include).
             }
         }
 
@@ -1134,7 +1153,7 @@ int err = 0;
 
     struct sockaddr_in srvAddr;
     srvAddr.sin_family = AF_INET;
-    srvAddr.sin_addr.s_addr = htonl(INADDR_ANY);
+    srvAddr.sin_addr.s_addr = htonl(INADDR_ANY); // NOLINT (include).
     srvAddr.sin_port = 0;
     err = bind(_fd, (struct sockaddr *) &srvAddr, sizeof(srvAddr));
     if (err) {
@@ -1147,7 +1166,7 @@ int err = 0;
 #endif
     }
 
-    std::string sPort = std::to_string(htons(_serverInfo.port));
+    std::string sPort = std::to_string(htons(_serverInfo.port)); // NOLINT (include).
     struct addrinfo hints = {}, *address_list = NULL;
     hints.ai_family = AF_INET;
     hints.ai_socktype = SOCK_DGRAM;