feat(runtime): forward stdout and stderr to os_log for the CLI

NativeScript/NativeScript.mm

@@ -11,6 +11,7 @@
 #include "runtime/NativeScriptException.h"
 #include "runtime/Runtime.h"
 #include "runtime/RuntimeConfig.h"
+#include "runtime/StdioForwarder.h"
 #include "runtime/Tasks.h"
 
 using namespace v8;
@@ -242,6 +243,7 @@ - (instancetype)initializeWithConfig:(Config*)config {
     RuntimeConfig.LogToSystemConsole = [config LogToSystemConsole];
 
     Runtime::Initialize();
+    StartStdioForwarding();
     DestroyMainRuntime();
     runtime_ = new Runtime();
 

NativeScript/runtime/Helpers.h

@@ -358,18 +358,20 @@ void LogBacktrace(int skip = 1);
 // Whether split messages should carry markers for the CLI to stitch them with.
 bool ShouldMarkLogChunks();
 
+bool IsDevNull(int fd);
+
 #if TNS_HAVE_OS_LOG
 // The prefix is repeated on every chunk, so that each stays a complete log line.
 static inline void TNS_WriteToOsLog(const char* message, os_log_type_t type = OS_LOG_TYPE_DEFAULT,
-                                    std::string_view prefix = "") {
+                                    std::string_view prefix = "", os_log_t log = OS_LOG_DEFAULT) {
   ForEachLogChunk(message, kMaxLogChunkBytes - prefix.size(),
                   [&](std::string_view chunk, LogChunkBreak chunkBreak) {
                     const char* marker = "";
                     if (chunkBreak != LogChunkBreak::kNone && ShouldMarkLogChunks()) {
                       marker = chunkBreak == LogChunkBreak::kLine ? kLogChunkLineMarker
                                                                   : kLogChunkJoinMarker;
                     }
-                    os_log_with_type(OS_LOG_DEFAULT, type, "%{public}.*s%{public}.*s%{public}s",
+                    os_log_with_type(log, type, "%{public}.*s%{public}.*s%{public}s",
                                      static_cast<int>(prefix.size()), prefix.data(),
                                      static_cast<int>(chunk.size()), chunk.data(), marker);
                   });

NativeScript/runtime/Helpers.mm

@@ -493,7 +493,7 @@ void WriteDebugLine(tns::LogCategory category, const char* message) {
   }
 }
 
-static bool IsDevNull(int fd) {
+bool tns::IsDevNull(int fd) {
   struct stat target;
   struct stat devNull;
   return fstat(fd, &target) == 0 && stat("/dev/null", &devNull) == 0 &&

NativeScript/runtime/StdioForwarder.h

@@ -0,0 +1,14 @@
+#ifndef StdioForwarder_h
+#define StdioForwarder_h
+
+namespace tns {
+
+// Sends what the app writes to stdout and stderr (print(), NSLog on devices) to
+// os_log. Without a console those go to /dev/null, and a process can't be
+// attached to later: its stdio is fixed at launch. Only debug builds whose CLI
+// asks for it through the forwardStdio key of the app's package.json do this.
+void StartStdioForwarding();
+
+}  // namespace tns
+
+#endif /* StdioForwarder_h */

NativeScript/runtime/StdioForwarder.mm

@@ -0,0 +1,99 @@
+#include "StdioForwarder.h"
+#include <Foundation/Foundation.h>
+#include <TargetConditionals.h>
+#include <dispatch/dispatch.h>
+#include <os/log.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <memory>
+#include <mutex>
+#include <string>
+#include "Helpers.h"
+#include "Runtime.h"
+#include "RuntimeConfig.h"
+
+namespace tns {
+
+namespace {
+
+// The CLI tells these entries apart from JS console output by this subsystem.
+constexpr const char* kStdioSubsystem = "org.nativescript.stdio";
+
+// A longer line goes out in parts instead of growing the buffer without limit.
+constexpr size_t kMaxBufferedLineBytes = 64 * 1024;
+
+void Forward(int fd, const char* category, dispatch_queue_t queue) {
+  int fds[2];
+  if (pipe(fds) != 0) {
+    return;
+  }
+  if (dup2(fds[1], fd) < 0) {
+    close(fds[0]);
+    close(fds[1]);
+    return;
+  }
+  close(fds[1]);
+
+  int readEnd = fds[0];
+  os_log_t log = os_log_create(kStdioSubsystem, category);
+  auto pending = std::make_shared<std::string>();
+  dispatch_source_t source = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, readEnd, 0, queue);
+  dispatch_source_set_event_handler(source, ^{
+    char buffer[4096];
+    ssize_t count = read(readEnd, buffer, sizeof(buffer));
+    if (count <= 0) {
+      return;
+    }
+    pending->append(buffer, count);
+
+    size_t start = 0;
+    size_t end;
+    while ((end = pending->find('\n', start)) != std::string::npos) {
+      TNS_WriteToOsLog(pending->substr(start, end - start).c_str(), OS_LOG_TYPE_DEFAULT, "", log);
+      start = end + 1;
+    }
+    pending->erase(0, start);
+
+    if (pending->size() >= kMaxBufferedLineBytes) {
+      TNS_WriteToOsLog(pending->c_str(), OS_LOG_TYPE_DEFAULT, "", log);
+      pending->clear();
+    }
+  });
+  dispatch_resume(source);
+}
+
+}  // namespace
+
+void StartStdioForwarding() {
+  static std::once_flag once;
+  std::call_once(once, [] {
+    if (!RuntimeConfig.IsDebug || RuntimeConfig.ApplicationPath.empty()) {
+      return;
+    }
+
+    id value = Runtime::GetAppConfigValue("forwardStdio");
+    if (![value isKindOfClass:[NSNumber class]] || ![value boolValue] ||
+        !IsDevNull(STDOUT_FILENO)) {
+      return;
+    }
+
+    // Decided once and from stdout, which is about to stop being /dev/null.
+    ShouldMarkLogChunks();
+
+    // Otherwise stdout is fully buffered into a pipe, and print() only shows up
+    // when the buffer fills.
+    setvbuf(stdout, nullptr, _IOLBF, 0);
+
+    // Serial, so that the chunks of a split line stay together.
+    dispatch_queue_t queue =
+        dispatch_queue_create("org.nativescript.stdio", DISPATCH_QUEUE_SERIAL);
+    Forward(STDOUT_FILENO, "stdout", queue);
+#if !TARGET_OS_SIMULATOR
+    // On the simulator NSLog reaches the unified log as well, so forwarding
+    // stderr there would print it twice.
+    Forward(STDERR_FILENO, "stderr", queue);
+#endif
+  });
+}
+
+}  // namespace tns

v8ios.xcodeproj/project.pbxproj

@@ -340,6 +340,8 @@
 		A1B2C3D40000000000000004 /* WorkerInspectorClient.mm in Sources */ = {isa = PBXBuildFile; fileRef = A1B2C3D40000000000000002 /* WorkerInspectorClient.mm */; };
 		F6191AB129C0FCE8003F588F /* InspectorServer.h in Headers */ = {isa = PBXBuildFile; fileRef = F6191AA929C0FCE7003F588F /* InspectorServer.h */; };
 		F6191AB229C0FCE8003F588F /* InspectorServer.mm in Sources */ = {isa = PBXBuildFile; fileRef = F6191AAA29C0FCE7003F588F /* InspectorServer.mm */; settings = {COMPILER_FLAGS = "-fobjc-arc"; }; };
+		A1C0DE5400000000000000A4 /* StdioForwarder.h in Headers */ = {isa = PBXBuildFile; fileRef = A1C0DE5200000000000000A2 /* StdioForwarder.h */; };
+		A1C0DE5500000000000000A5 /* StdioForwarder.mm in Sources */ = {isa = PBXBuildFile; fileRef = A1C0DE5300000000000000A3 /* StdioForwarder.mm */; };
 		F6191AB629C0FF87003F588F /* utils.h in Headers */ = {isa = PBXBuildFile; fileRef = F6191AB429C0FF86003F588F /* utils.h */; };
 		F6191AB729C0FF87003F588F /* utils.mm in Sources */ = {isa = PBXBuildFile; fileRef = F6191AB529C0FF86003F588F /* utils.mm */; };
 		D3FA1E7A0000000000000004 /* NativeScriptDefaultMetadata.c in Sources */ = {isa = PBXBuildFile; fileRef = D3FA1E7A0000000000000002 /* NativeScriptDefaultMetadata.c */; };
@@ -819,6 +821,8 @@
 		C2DDEB6B229EAC8200345BFE /* Console.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = Console.cpp; sourceTree = "<group>"; };
 		C2DDEB6D229EAC8200345BFE /* Helpers.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = Helpers.h; sourceTree = "<group>"; };
 		A1C0DE5100000000000000A1 /* LogChunks.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = LogChunks.h; sourceTree = "<group>"; };
+		A1C0DE5200000000000000A2 /* StdioForwarder.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = StdioForwarder.h; sourceTree = "<group>"; };
+		A1C0DE5300000000000000A3 /* StdioForwarder.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = StdioForwarder.mm; sourceTree = "<group>"; };
 		C2DDEB6E229EAC8200345BFE /* Metadata.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = Metadata.h; sourceTree = "<group>"; };
 		C2DDEB6F229EAC8200345BFE /* ArrayAdapter.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ArrayAdapter.h; sourceTree = "<group>"; };
 		C2DDEB70229EAC8200345BFE /* Metadata.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = Metadata.mm; sourceTree = "<group>"; };
@@ -1499,6 +1503,8 @@
 				C266569C22B282BA00EE15CC /* FunctionReference.cpp */,
 				C2DDEB6D229EAC8200345BFE /* Helpers.h */,
 				A1C0DE5100000000000000A1 /* LogChunks.h */,
+				A1C0DE5200000000000000A2 /* StdioForwarder.h */,
+				A1C0DE5300000000000000A3 /* StdioForwarder.mm */,
 				C2DDEB7D229EAC8200345BFE /* Helpers.mm */,
 				AA5DBFD12EC191F8008D12F9 /* HttpLoader.h */,
 				AA5DBFD22EC191F8008D12F9 /* HttpLoader.mm */,
@@ -1669,6 +1675,7 @@
 				C2DDEB97229EAC8300345BFE /* Metadata.h in Headers */,
 				C247C16522F82842001D2CA2 /* v8-platform.h in Headers */,
 				F6191AB129C0FCE8003F588F /* InspectorServer.h in Headers */,
+				A1C0DE5400000000000000A4 /* StdioForwarder.h in Headers */,
 				C247C16722F82842001D2CA2 /* libplatform.h in Headers */,
 				C2DDEBA4229EAC8300345BFE /* Runtime.h in Headers */,
 				F1CB51842D5C37100042555E /* URLPatternImpl.h in Headers */,
@@ -2352,6 +2359,7 @@
 				C266569722AFFFB000EE15CC /* Reference.cpp in Sources */,
 				6573B9EE291FE5B700B0ED7C /* JSIRuntime.m in Sources */,
 				F6191AB229C0FCE8003F588F /* InspectorServer.mm in Sources */,
+				A1C0DE5500000000000000A5 /* StdioForwarder.mm in Sources */,
 				6573B9D3291FE29F00B0ED7C /* HostProxy.cpp in Sources */,
 				6573B9E5291FE2A700B0ED7C /* jsi.cpp in Sources */,
 				C2DDEBB3229EAC8300345BFE /* ClassBuilder.mm in Sources */,