[lldb-dap] When sending a DAP Output Event break each message into separate lines. (llvm#105456)

Previously, when output like `"hello\nworld\n"` was produced by lldb (or
the process) the message would be sent as a single Output event. By
being a single event this causes VS Code to treat this as a single
message in the console when handling displaying and filtering in the
Debug Console.

Instead, with these changes we send each line as its own event. This
results in VS Code representing each line of output from lldb-dap as an
individual output message.

Resolves llvm#105444

(cherry picked from commit 30ca06c)

Author: ashgti

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));