llvmbot wrote:

<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lldb

Author: John Harrison (ashgti)

<details>
<summary>Changes</summary>

Reapply "[lldb] Update JSONTransport to use MainLoop for reading." (#<!-- 
-->152155)

This reverts commit cd40281685f642ad879e33f3fda8d1faa136ebf4.

This also includes some updates to try to address the platforms with failing 
tests.

I updated the JSONTransport and tests to use std::function instead of 
llvm:unique_function. I think the tests were failing due to the unique_function 
not being moved correctly in the loop on some platforms.

---

Patch is 54.04 KiB, truncated to 20.00 KiB below, full version: 
https://github.com/llvm/llvm-project/pull/152367.diff


11 Files Affected:

- (modified) lldb/include/lldb/Host/JSONTransport.h (+84-29) 
- (modified) lldb/source/Host/common/JSONTransport.cpp (+53-114) 
- (modified) lldb/test/API/tools/lldb-dap/io/TestDAP_io.py (+17-10) 
- (modified) lldb/tools/lldb-dap/DAP.cpp (+65-63) 
- (modified) lldb/tools/lldb-dap/DAP.h (+7) 
- (modified) lldb/tools/lldb-dap/Transport.h (+1-1) 
- (modified) lldb/unittests/DAP/DAPTest.cpp (+5-6) 
- (modified) lldb/unittests/DAP/TestBase.cpp (+17-9) 
- (modified) lldb/unittests/DAP/TestBase.h (+20) 
- (modified) lldb/unittests/Host/JSONTransportTest.cpp (+228-71) 
- (modified) lldb/unittests/ProtocolServer/ProtocolMCPServerTest.cpp (+76-55) 


``````````diff
diff --git a/lldb/include/lldb/Host/JSONTransport.h 
b/lldb/include/lldb/Host/JSONTransport.h
index 4087cdf2b42f7..98bce6e265356 100644
--- a/lldb/include/lldb/Host/JSONTransport.h
+++ b/lldb/include/lldb/Host/JSONTransport.h
@@ -13,13 +13,15 @@
 #ifndef LLDB_HOST_JSONTRANSPORT_H
 #define LLDB_HOST_JSONTRANSPORT_H
 
+#include "lldb/Host/MainLoopBase.h"
 #include "lldb/lldb-forward.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/JSON.h"
-#include <chrono>
+#include <string>
 #include <system_error>
+#include <vector>
 
 namespace lldb_private {
 
@@ -28,27 +30,33 @@ class TransportEOFError : public 
llvm::ErrorInfo<TransportEOFError> {
   static char ID;
 
   TransportEOFError() = default;
-
-  void log(llvm::raw_ostream &OS) const override {
-    OS << "transport end of file reached";
-  }
+  void log(llvm::raw_ostream &OS) const override { OS << "transport EOF"; }
   std::error_code convertToErrorCode() const override {
-    return llvm::inconvertibleErrorCode();
+    return std::make_error_code(std::errc::io_error);
   }
 };
 
-class TransportTimeoutError : public llvm::ErrorInfo<TransportTimeoutError> {
+class TransportUnhandledContentsError
+    : public llvm::ErrorInfo<TransportUnhandledContentsError> {
 public:
   static char ID;
 
-  TransportTimeoutError() = default;
+  explicit TransportUnhandledContentsError(std::string unhandled_contents)
+      : m_unhandled_contents(unhandled_contents) {}
 
   void log(llvm::raw_ostream &OS) const override {
-    OS << "transport operation timed out";
+    OS << "transport EOF with unhandled contents " << m_unhandled_contents;
   }
   std::error_code convertToErrorCode() const override {
-    return std::make_error_code(std::errc::timed_out);
+    return std::make_error_code(std::errc::bad_message);
   }
+
+  const std::string &getUnhandledContents() const {
+    return m_unhandled_contents;
+  }
+
+private:
+  std::string m_unhandled_contents;
 };
 
 class TransportInvalidError : public llvm::ErrorInfo<TransportInvalidError> {
@@ -68,6 +76,10 @@ class TransportInvalidError : public 
llvm::ErrorInfo<TransportInvalidError> {
 /// A transport class that uses JSON for communication.
 class JSONTransport {
 public:
+  using ReadHandleUP = MainLoopBase::ReadHandleUP;
+  template <typename T>
+  using Callback = std::function<void(MainLoopBase &, const 
llvm::Expected<T>)>;
+
   JSONTransport(lldb::IOObjectSP input, lldb::IOObjectSP output);
   virtual ~JSONTransport() = default;
 
@@ -83,24 +95,69 @@ class JSONTransport {
     return WriteImpl(message);
   }
 
-  /// Reads the next message from the input stream.
+  /// Registers the transport with the MainLoop.
   template <typename T>
-  llvm::Expected<T> Read(const std::chrono::microseconds &timeout) {
-    llvm::Expected<std::string> message = ReadImpl(timeout);
-    if (!message)
-      return message.takeError();
-    return llvm::json::parse<T>(/*JSON=*/*message);
+  llvm::Expected<ReadHandleUP> RegisterReadObject(MainLoopBase &loop,
+                                                  Callback<T> callback) {
+    Status error;
+    ReadHandleUP handle = loop.RegisterReadObject(
+        m_input,
+        [&](MainLoopBase &loop) {
+          char buffer[kReadBufferSize];
+          size_t len = sizeof(buffer);
+          if (llvm::Error error = m_input->Read(buffer, len).takeError()) {
+            callback(loop, std::move(error));
+            return;
+          }
+
+          if (len)
+            m_buffer.append(std::string(buffer, len));
+
+          // If the buffer has contents, try parsing any pending messages.
+          if (!m_buffer.empty()) {
+            llvm::Expected<std::vector<std::string>> messages = Parse();
+            if (llvm::Error error = messages.takeError()) {
+              callback(loop, std::move(error));
+              return;
+            }
+
+            for (const auto &message : *messages)
+              if constexpr (std::is_same<T, std::string>::value)
+                callback(loop, message);
+              else
+                callback(loop, llvm::json::parse<T>(message));
+          }
+
+          // On EOF, notify the callback after the remaining messages were
+          // handled.
+          if (len == 0) {
+            if (m_buffer.empty())
+              callback(loop, llvm::make_error<TransportEOFError>());
+            else
+              callback(loop, llvm::make_error<TransportUnhandledContentsError>(
+                                 m_buffer));
+          }
+        },
+        error);
+    if (error.Fail())
+      return error.takeError();
+    return handle;
   }
 
 protected:
+  template <typename... Ts> inline auto Logv(const char *Fmt, Ts &&...Vals) {
+    Log(llvm::formatv(Fmt, std::forward<Ts>(Vals)...).str());
+  }
   virtual void Log(llvm::StringRef message);
 
   virtual llvm::Error WriteImpl(const std::string &message) = 0;
-  virtual llvm::Expected<std::string>
-  ReadImpl(const std::chrono::microseconds &timeout) = 0;
+  virtual llvm::Expected<std::vector<std::string>> Parse() = 0;
 
   lldb::IOObjectSP m_input;
   lldb::IOObjectSP m_output;
+  std::string m_buffer;
+
+  static constexpr size_t kReadBufferSize = 1024;
 };
 
 /// A transport class for JSON with a HTTP header.
@@ -111,14 +168,13 @@ class HTTPDelimitedJSONTransport : public JSONTransport {
   virtual ~HTTPDelimitedJSONTransport() = default;
 
 protected:
-  virtual llvm::Error WriteImpl(const std::string &message) override;
-  virtual llvm::Expected<std::string>
-  ReadImpl(const std::chrono::microseconds &timeout) override;
-
-  // FIXME: Support any header.
-  static constexpr llvm::StringLiteral kHeaderContentLength =
-      "Content-Length: ";
-  static constexpr llvm::StringLiteral kHeaderSeparator = "\r\n\r\n";
+  llvm::Error WriteImpl(const std::string &message) override;
+  llvm::Expected<std::vector<std::string>> Parse() override;
+
+  static constexpr llvm::StringLiteral kHeaderContentLength = "Content-Length";
+  static constexpr llvm::StringLiteral kHeaderFieldSeparator = ":";
+  static constexpr llvm::StringLiteral kHeaderSeparator = "\r\n";
+  static constexpr llvm::StringLiteral kEndOfHeader = "\r\n\r\n";
 };
 
 /// A transport class for JSON RPC.
@@ -129,9 +185,8 @@ class JSONRPCTransport : public JSONTransport {
   virtual ~JSONRPCTransport() = default;
 
 protected:
-  virtual llvm::Error WriteImpl(const std::string &message) override;
-  virtual llvm::Expected<std::string>
-  ReadImpl(const std::chrono::microseconds &timeout) override;
+  llvm::Error WriteImpl(const std::string &message) override;
+  llvm::Expected<std::vector<std::string>> Parse() override;
 
   static constexpr llvm::StringLiteral kMessageSeparator = "\n";
 };
diff --git a/lldb/source/Host/common/JSONTransport.cpp 
b/lldb/source/Host/common/JSONTransport.cpp
index 546c12c8f7114..c3a3b06ecbced 100644
--- a/lldb/source/Host/common/JSONTransport.cpp
+++ b/lldb/source/Host/common/JSONTransport.cpp
@@ -7,17 +7,14 @@
 
//===----------------------------------------------------------------------===//
 
 #include "lldb/Host/JSONTransport.h"
-#include "lldb/Utility/IOObject.h"
 #include "lldb/Utility/LLDBLog.h"
 #include "lldb/Utility/Log.h"
-#include "lldb/Utility/SelectHelper.h"
 #include "lldb/Utility/Status.h"
 #include "lldb/lldb-forward.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/raw_ostream.h"
-#include <optional>
 #include <string>
 #include <utility>
 
@@ -25,64 +22,6 @@ using namespace llvm;
 using namespace lldb;
 using namespace lldb_private;
 
-/// ReadFull attempts to read the specified number of bytes. If EOF is
-/// encountered, an empty string is returned.
-static Expected<std::string>
-ReadFull(IOObject &descriptor, size_t length,
-         std::optional<std::chrono::microseconds> timeout = std::nullopt) {
-  if (!descriptor.IsValid())
-    return llvm::make_error<TransportInvalidError>();
-
-  bool timeout_supported = true;
-  // FIXME: SelectHelper does not work with NativeFile on Win32.
-#if _WIN32
-  timeout_supported = descriptor.GetFdType() == IOObject::eFDTypeSocket;
-#endif
-
-  if (timeout && timeout_supported) {
-    SelectHelper sh;
-    sh.SetTimeout(*timeout);
-    sh.FDSetRead(
-        reinterpret_cast<lldb::socket_t>(descriptor.GetWaitableHandle()));
-    Status status = sh.Select();
-    if (status.Fail()) {
-      // Convert timeouts into a specific error.
-      if (status.GetType() == lldb::eErrorTypePOSIX &&
-          status.GetError() == ETIMEDOUT)
-        return make_error<TransportTimeoutError>();
-      return status.takeError();
-    }
-  }
-
-  std::string data;
-  data.resize(length);
-  Status status = descriptor.Read(data.data(), length);
-  if (status.Fail())
-    return status.takeError();
-
-  // Read returns '' on EOF.
-  if (length == 0)
-    return make_error<TransportEOFError>();
-
-  // Return the actual number of bytes read.
-  return data.substr(0, length);
-}
-
-static Expected<std::string>
-ReadUntil(IOObject &descriptor, StringRef delimiter,
-          std::optional<std::chrono::microseconds> timeout = std::nullopt) {
-  std::string buffer;
-  buffer.reserve(delimiter.size() + 1);
-  while (!llvm::StringRef(buffer).ends_with(delimiter)) {
-    Expected<std::string> next =
-        ReadFull(descriptor, buffer.empty() ? delimiter.size() : 1, timeout);
-    if (auto Err = next.takeError())
-      return std::move(Err);
-    buffer += *next;
-  }
-  return buffer.substr(0, buffer.size() - delimiter.size());
-}
-
 JSONTransport::JSONTransport(IOObjectSP input, IOObjectSP output)
     : m_input(std::move(input)), m_output(std::move(output)) {}
 
@@ -90,80 +29,80 @@ void JSONTransport::Log(llvm::StringRef message) {
   LLDB_LOG(GetLog(LLDBLog::Host), "{0}", message);
 }
 
-Expected<std::string>
-HTTPDelimitedJSONTransport::ReadImpl(const std::chrono::microseconds &timeout) 
{
-  if (!m_input || !m_input->IsValid())
-    return llvm::make_error<TransportInvalidError>();
+// Parses messages based on
+// https://microsoft.github.io/debug-adapter-protocol/overview#base-protocol
+Expected<std::vector<std::string>> HTTPDelimitedJSONTransport::Parse() {
+  std::vector<std::string> messages;
+  StringRef buffer = m_buffer;
+  while (buffer.contains(kEndOfHeader)) {
+    auto [headers, rest] = buffer.split(kEndOfHeader);
+    size_t content_length = 0;
+    // HTTP Headers are formatted like `<field-name> ':' [<field-value>]`.
+    for (const auto &header : llvm::split(headers, kHeaderSeparator)) {
+      auto [key, value] = header.split(kHeaderFieldSeparator);
+      // 'Content-Length' is the only meaningful key at the moment. Others are
+      // ignored.
+      if (!key.equals_insensitive(kHeaderContentLength))
+        continue;
+
+      value = value.trim();
+      if (!llvm::to_integer(value, content_length, 10))
+        return createStringError(std::errc::invalid_argument,
+                                 "invalid content length: %s",
+                                 value.str().c_str());
+    }
+
+    // Check if we have enough data.
+    if (content_length > rest.size())
+      break;
 
-  IOObject *input = m_input.get();
-  Expected<std::string> message_header =
-      ReadFull(*input, kHeaderContentLength.size(), timeout);
-  if (!message_header)
-    return message_header.takeError();
-  if (*message_header != kHeaderContentLength)
-    return createStringError(formatv("expected '{0}' and got '{1}'",
-                                     kHeaderContentLength, *message_header)
-                                 .str());
-
-  Expected<std::string> raw_length = ReadUntil(*input, kHeaderSeparator);
-  if (!raw_length)
-    return handleErrors(raw_length.takeError(),
-                        [&](const TransportEOFError &E) -> llvm::Error {
-                          return createStringError(
-                              "unexpected EOF while reading header separator");
-                        });
-
-  size_t length;
-  if (!to_integer(*raw_length, length))
-    return createStringError(
-        formatv("invalid content length {0}", *raw_length).str());
-
-  Expected<std::string> raw_json = ReadFull(*input, length);
-  if (!raw_json)
-    return handleErrors(
-        raw_json.takeError(), [&](const TransportEOFError &E) -> llvm::Error {
-          return createStringError("unexpected EOF while reading JSON");
-        });
-
-  Log(llvm::formatv("--> {0}", *raw_json).str());
-
-  return raw_json;
+    StringRef body = rest.take_front(content_length);
+    buffer = rest.drop_front(content_length);
+    messages.emplace_back(body.str());
+    Logv("--> {0}", body);
+  }
+
+  // Store the remainder of the buffer for the next read callback.
+  m_buffer = buffer.str();
+
+  return std::move(messages);
 }
 
 Error HTTPDelimitedJSONTransport::WriteImpl(const std::string &message) {
   if (!m_output || !m_output->IsValid())
     return llvm::make_error<TransportInvalidError>();
 
-  Log(llvm::formatv("<-- {0}", message).str());
+  Logv("<-- {0}", message);
 
   std::string Output;
   raw_string_ostream OS(Output);
-  OS << kHeaderContentLength << message.length() << kHeaderSeparator << 
message;
+  OS << kHeaderContentLength << kHeaderFieldSeparator << ' ' << 
message.length()
+     << kHeaderSeparator << kHeaderSeparator << message;
   size_t num_bytes = Output.size();
   return m_output->Write(Output.data(), num_bytes).takeError();
 }
 
-Expected<std::string>
-JSONRPCTransport::ReadImpl(const std::chrono::microseconds &timeout) {
-  if (!m_input || !m_input->IsValid())
-    return make_error<TransportInvalidError>();
-
-  IOObject *input = m_input.get();
-  Expected<std::string> raw_json =
-      ReadUntil(*input, kMessageSeparator, timeout);
-  if (!raw_json)
-    return raw_json.takeError();
+Expected<std::vector<std::string>> JSONRPCTransport::Parse() {
+  std::vector<std::string> messages;
+  StringRef buf = m_buffer;
+  while (buf.contains(kMessageSeparator)) {
+    auto [raw_json, rest] = buf.split(kMessageSeparator);
+    buf = rest;
+    messages.emplace_back(raw_json.str());
+    Logv("--> {0}", raw_json);
+  }
 
-  Log(llvm::formatv("--> {0}", *raw_json).str());
+  // Store the remainder of the buffer for the next read callback.
+  m_buffer = buf.str();
 
-  return *raw_json;
+  return messages;
 }
 
 Error JSONRPCTransport::WriteImpl(const std::string &message) {
   if (!m_output || !m_output->IsValid())
     return llvm::make_error<TransportInvalidError>();
 
-  Log(llvm::formatv("<-- {0}", message).str());
+  Logv("<-- {0}", message);
 
   std::string Output;
   llvm::raw_string_ostream OS(Output);
@@ -173,5 +112,5 @@ Error JSONRPCTransport::WriteImpl(const std::string 
&message) {
 }
 
 char TransportEOFError::ID;
-char TransportTimeoutError::ID;
+char TransportUnhandledContentsError::ID;
 char TransportInvalidError::ID;
diff --git a/lldb/test/API/tools/lldb-dap/io/TestDAP_io.py 
b/lldb/test/API/tools/lldb-dap/io/TestDAP_io.py
index b72b98de412b4..af5c62a8c4eb5 100644
--- a/lldb/test/API/tools/lldb-dap/io/TestDAP_io.py
+++ b/lldb/test/API/tools/lldb-dap/io/TestDAP_io.py
@@ -8,6 +8,9 @@
 import lldbdap_testcase
 import dap_server
 
+EXIT_FAILURE = 1
+EXIT_SUCCESS = 0
+
 
 class TestDAP_io(lldbdap_testcase.DAPTestCaseBase):
     def launch(self):
@@ -41,40 +44,44 @@ def test_eof_immediately(self):
         """
         process = self.launch()
         process.stdin.close()
-        self.assertEqual(process.wait(timeout=5.0), 0)
+        self.assertEqual(process.wait(timeout=5.0), EXIT_SUCCESS)
 
     def test_invalid_header(self):
         """
-        lldb-dap handles invalid message headers.
+        lldb-dap returns a failure exit code when the input stream is closed
+        with a malformed request header.
         """
         process = self.launch()
-        process.stdin.write(b"not the corret message header")
+        process.stdin.write(b"not the correct message header")
         process.stdin.close()
-        self.assertEqual(process.wait(timeout=5.0), 1)
+        self.assertEqual(process.wait(timeout=5.0), EXIT_FAILURE)
 
     def test_partial_header(self):
         """
-        lldb-dap handles parital message headers.
+        lldb-dap returns a failure exit code when the input stream is closed
+        with an incomplete message header is in the message buffer.
         """
         process = self.launch()
         process.stdin.write(b"Content-Length: ")
         process.stdin.close()
-        self.assertEqual(process.wait(timeout=5.0), 1)
+        self.assertEqual(process.wait(timeout=5.0), EXIT_FAILURE)
 
     def test_incorrect_content_length(self):
         """
-        lldb-dap handles malformed content length headers.
+        lldb-dap returns a failure exit code when reading malformed content
+        length headers.
         """
         process = self.launch()
         process.stdin.write(b"Content-Length: abc")
         process.stdin.close()
-        self.assertEqual(process.wait(timeout=5.0), 1)
+        self.assertEqual(process.wait(timeout=5.0), EXIT_FAILURE)
 
     def test_partial_content_length(self):
         """
-        lldb-dap handles partial messages.
+        lldb-dap returns a failure exit code when the input stream is closed
+        with a partial message in the message buffer.
         """
         process = self.launch()
         process.stdin.write(b"Content-Length: 10\r\n\r\n{")
         process.stdin.close()
-        self.assertEqual(process.wait(timeout=5.0), 1)
+        self.assertEqual(process.wait(timeout=5.0), EXIT_FAILURE)
diff --git a/lldb/tools/lldb-dap/DAP.cpp b/lldb/tools/lldb-dap/DAP.cpp
index cbd3b14463e25..55c5c9347bf6f 100644
--- a/lldb/tools/lldb-dap/DAP.cpp
+++ b/lldb/tools/lldb-dap/DAP.cpp
@@ -23,13 +23,14 @@
 #include "Transport.h"
 #include "lldb/API/SBBreakpoint.h"
 #include "lldb/API/SBCommandInterpreter.h"
-#include "lldb/API/SBCommandReturnObject.h"
 #include "lldb/API/SBEvent.h"
 #include "lldb/API/SBLanguageRuntime.h"
 #include "lldb/API/SBListener.h"
 #include "lldb/API/SBProcess.h"
 #include "lldb/API/SBStream.h"
-#include "lldb/Utility/IOObject.h"
+#include "lldb/Host/JSONTransport.h"
+#include "lldb/Host/MainLoop.h"
+#include "lldb/Host/MainLoopBase.h"
 #include "lldb/Utility/Status.h"
 #include "lldb/lldb-defines.h"
 #include "lldb/lldb-enumerations.h"
@@ -52,7 +53,7 @@
 #include <cstdarg>
 #include <cstdint>
 #include <cstdio>
-#include <fstream>
+#include <functional>
 #include <future>
 #include <memory>
 #include <mutex>
@@ -919,6 +920,8 @@ llvm::Error DAP::Disconnect(bool terminateDebuggee) {
   SendTerminatedEvent();
 
   disconnecting = true;
+  m_loop.AddPendingCallback(
+      [](MainLoopBase &loop) { loop.RequestTermination(); });
 
   return ToError(error);
 }
@@ -949,75 +952,74 @@ static std::optional<T> getArgumentsIfRequest(const 
Message &pm,
   return args;
 }
 
-llvm::Error DAP::Loop() {
-  // Can't use \a std::future<llvm::Error> because it doesn't compile on
-  // Windows.
-  std::future<lldb::SBError> queue_reader =
-      std::async(std::launch::async, [&]() -> lldb::SBError {
-        llvm::set_thread_name(transport.GetClientName() + 
".transport_handler");
-        auto cleanup = llvm::make_scope_exit([&]() {
-          // Ensure we're marked as disconnecting when the reader exits.
-          disconnecting = true;
-          m_queue_cv.notify_all();
-        });
-
-        while (!disconnecting) {
-          llvm::Expected<Message> next =
-              transport.Read<protocol::Message>(std::chrono::seconds(1));
-          if (next.errorIsA<TransportEOFError>()) {
-            consumeError(next.takeError());
-            break;
-          }
+Status DAP::TransportHandler() {
+  llvm::set_thread_name(transport.GetClientName() + ".transport_handler");
 
-          // If the read timed out, continue to check if we should disconnect.
-          if (next.errorIsA<TransportTimeoutError>()) {
-            consumeError(next.takeError());
-            continue;
-          }
+  auto cleanup = llvm::make_scope_exit([&]() {
+    // Ensure we're marked as disconnecting when the reader exits.
+    disconnecting = true;
+    m_queue_cv.notify_all();
+  });
 
-          if (llvm::Error err = next.takeError()) {
-            lldb::SBError errWrapper;
-            errWrapper.SetErrorString(llvm::toString(std::move(err)).c_str());
-            return errWrapper;
-          }
+  Status ...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/152367
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