[lldb-dap] When sending a DAP Output Event break each message into separate lines.

lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py

@@ -202,6 +202,11 @@ def collect_console(self, timeout_secs, pattern=None):
             "console", timeout_secs=timeout_secs, pattern=pattern
         )
 
+    def collect_stdout(self, timeout_secs, pattern=None):
+        return self.dap_server.collect_output(
+            "stdout", timeout_secs=timeout_secs, pattern=pattern
+        )
+
     def get_local_as_int(self, name, threadId=None):
         value = self.dap_server.get_local_variable_value(name, threadId=threadId)
         # 'value' may have the variable value and summary.

lldb/test/API/tools/lldb-dap/output/Makefile

@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules

lldb/test/API/tools/lldb-dap/output/TestDAP_output.py

@@ -0,0 +1,31 @@
+"""
+Test lldb-dap output events
+"""
+
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+import lldbdap_testcase
+
+
+class TestDAP_output(lldbdap_testcase.DAPTestCaseBase):
+    def test_output(self):
+        program = self.getBuildArtifact("a.out")
+        self.build_and_launch(program)
+        source = "main.c"
+        lines = [line_number(source, "// breakpoint 1")]
+        breakpoint_ids = self.set_source_breakpoints(source, lines)
+        self.continue_to_breakpoints(breakpoint_ids)
+
+        # Ensure partial messages are still sent.
+        output = self.collect_stdout(timeout_secs=1.0, pattern="abcdef")
+        self.assertTrue(output and len(output) > 0, "expect no program output")
+
+        self.continue_to_exit()
+
+        output += self.get_stdout(timeout=lldbdap_testcase.DAPTestCaseBase.timeoutval)
+        self.assertTrue(output and len(output) > 0, "expect no program output")
+        self.assertIn(
+            "abcdefghi\r\nhello world\r\n",
+            output,
+            'full output not found in: ' + output,
+        )

lldb/test/API/tools/lldb-dap/output/main.c

@@ -0,0 +1,12 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int main() {
+  // Ensure multiple partial lines are detected and sent.
+  printf("abc");
+  printf("def");
+  printf("ghi\n");
+  printf("hello world\n"); // breakpoint 1
+  return 0;
+}

lldb/tools/lldb-dap/DAP.cpp

@@ -294,8 +294,6 @@ void DAP::SendOutput(OutputType o, const llvm::StringRef output) {
   if (output.empty())
     return;
 
-  llvm::json::Object event(CreateEventObject("output"));
-  llvm::json::Object body;
   const char *category = nullptr;
   switch (o) {
   case OutputType::Console:
@@ -311,10 +309,22 @@ void DAP::SendOutput(OutputType o, const llvm::StringRef output) {
     category = "telemetry";
     break;
   }
-  body.try_emplace("category", category);
-  EmplaceSafeString(body, "output", output.str());
-  event.try_emplace("body", std::move(body));
-  SendJSON(llvm::json::Value(std::move(event)));
+
+  // Send each line of output as an individual event, including the newline if
+  // present.
+  ::size_t idx = 0;
+  do {
+    ::size_t end = output.find('\n', idx);
+    if (end == llvm::StringRef::npos)
+      end = output.size() - 1;
+    llvm::json::Object event(CreateEventObject("output"));
+    llvm::json::Object body;
+    body.try_emplace("category", category);
+    EmplaceSafeString(body, "output", output.slice(idx, end + 1).str());
+    event.try_emplace("body", std::move(body));
+    SendJSON(llvm::json::Value(std::move(event)));
+    idx = end + 1;
+  } while (idx < output.size());
 }
 
 // interface ProgressStartEvent extends Event {

lldb/tools/lldb-dap/DAP.h

@@ -68,8 +68,12 @@ namespace lldb_dap {
 
 typedef llvm::DenseMap<uint32_t, SourceBreakpoint> SourceBreakpointMap;
 typedef llvm::StringMap<FunctionBreakpoint> FunctionBreakpointMap;
+
 enum class OutputType { Console, Stdout, Stderr, Telemetry };
 
+/// Buffer size for handling output events.
+constexpr uint64_t OutputBufferSize = (1u << 12);
+
 enum DAPBroadcasterBits {
   eBroadcastBitStopEventThread = 1u << 0,
   eBroadcastBitStopProgressThread = 1u << 1

lldb/tools/lldb-dap/OutputRedirector.cpp

@@ -13,6 +13,7 @@
 #include <unistd.h>
 #endif
 
+#include "DAP.h"
 #include "OutputRedirector.h"
 #include "llvm/ADT/StringRef.h"
 
@@ -42,7 +43,7 @@ Error RedirectFd(int fd, std::function<void(llvm::StringRef)> callback) {
 
   int read_fd = new_fd[0];
   std::thread t([read_fd, callback]() {
-    char buffer[4096];
+    char buffer[OutputBufferSize];
     while (true) {
       ssize_t bytes_count = read(read_fd, &buffer, sizeof(buffer));
       if (bytes_count == 0)

lldb/tools/lldb-dap/lldb-dap.cpp

@@ -399,7 +399,7 @@ void SendProcessEvent(LaunchMethod launch_method) {
 // Grab any STDOUT and STDERR from the process and send it up to VS Code
 // via an "output" event to the "stdout" and "stderr" categories.
 void SendStdOutStdErr(lldb::SBProcess &process) {
-  char buffer[1024];
+  char buffer[OutputBufferSize];
   size_t count;
   while ((count = process.GetSTDOUT(buffer, sizeof(buffer))) > 0)
     g_dap.SendOutput(OutputType::Stdout, llvm::StringRef(buffer, count));