When sending a DAP Output Event break each message into separate lines.

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.

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 +1,37 @@
+"""
+Test lldb-dap output events
+"""
+
+import dap_server
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+import lldbdap_testcase
+import re
+
+
+class TestDAP_output(lldbdap_testcase.DAPTestCaseBase):
+    def test_output(self):
+        program = self.getBuildArtifact("a.out")
+        self.build_and_launch(program)
+        source = "main.c"
+        main_source_path = self.getSourcePath(source)
+        lines = [line_number(source, "// breakpoint 1")]
+        breakpoint_ids = self.set_source_breakpoints(source, lines)
+        self.continue_to_breakpoints(breakpoint_ids)
+        
+        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 +1,11 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int main() {
+  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 {