[lldb-vscode] Allow specifying a custom escape prefix for LLDB commands (#69238)

We've been using the backtick as our escape character, however that
leads to a weird experience on VS Code, because on most hosts, as soon
as you type the backtick on VS Code, the IDE will introduce another
backtick. As changing the default escape character might be out of
question because other plugins might rely on it, we can instead
introduce an option to change this variable upon lldb-vscode
initialization.
FWIW, my users will be using : instead ot the backtick.

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

@@ -731,6 +731,7 @@ class DebugCommunication(object):
         postRunCommands=None,
         enableAutoVariableSummaries=False,
         enableSyntheticChildDebugging=False,
+        commandEscapePrefix="`",
     ):
         args_dict = {"program": program}
         if args:
@@ -774,6 +775,7 @@ class DebugCommunication(object):
             args_dict["postRunCommands"] = postRunCommands
         args_dict["enableAutoVariableSummaries"] = enableAutoVariableSummaries
         args_dict["enableSyntheticChildDebugging"] = enableSyntheticChildDebugging
+        args_dict["commandEscapePrefix"] = commandEscapePrefix
         command_dict = {"command": "launch", "type": "request", "arguments": args_dict}
         response = self.send_recv(command_dict)
 
@@ -1015,7 +1017,12 @@ class DebugCommunication(object):
 
 class DebugAdaptorServer(DebugCommunication):
     def __init__(
-        self, executable=None, port=None, init_commands=[], log_file=None, env=None
+        self,
+        executable=None,
+        port=None,
+        init_commands=[],
+        log_file=None,
+        env=None,
     ):
         self.process = None
         if executable is not None:

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

@@ -351,6 +351,7 @@ class DAPTestCaseBase(TestBase):
         postRunCommands=None,
         enableAutoVariableSummaries=False,
         enableSyntheticChildDebugging=False,
+        commandEscapePrefix="`",
     ):
         """Sending launch request to dap"""
 
@@ -389,6 +390,7 @@ class DAPTestCaseBase(TestBase):
             postRunCommands=postRunCommands,
             enableAutoVariableSummaries=enableAutoVariableSummaries,
             enableSyntheticChildDebugging=enableSyntheticChildDebugging,
+            commandEscapePrefix=commandEscapePrefix,
         )
 
         if expectFailure:
@@ -425,6 +427,7 @@ class DAPTestCaseBase(TestBase):
         lldbDAPEnv=None,
         enableAutoVariableSummaries=False,
         enableSyntheticChildDebugging=False,
+        commandEscapePrefix="`",
     ):
         """Build the default Makefile target, create the DAP debug adaptor,
         and launch the process.
@@ -455,4 +458,5 @@ class DAPTestCaseBase(TestBase):
             postRunCommands=postRunCommands,
             enableAutoVariableSummaries=enableAutoVariableSummaries,
             enableSyntheticChildDebugging=enableSyntheticChildDebugging,
+            commandEscapePrefix=commandEscapePrefix,
         )

lldb/test/API/tools/lldb-dap/console/TestDAP_console.py

@@ -3,16 +3,18 @@ Test lldb-dap setBreakpoints request
 """
 
 import dap_server
+import lldbdap_testcase
+from lldbsuite.test import lldbutil
 from lldbsuite.test.decorators import *
 from lldbsuite.test.lldbtest import *
-from lldbsuite.test import lldbutil
-import lldbdap_testcase
 
 
 class TestDAP_console(lldbdap_testcase.DAPTestCaseBase):
-    def check_lldb_command(self, lldb_command, contains_string, assert_msg):
+    def check_lldb_command(
+        self, lldb_command, contains_string, assert_msg, command_escape_prefix="`"
+    ):
         response = self.dap_server.request_evaluate(
-            "`%s" % (lldb_command), context="repl"
+            f"{command_escape_prefix}{lldb_command}", context="repl"
         )
         output = response["body"]["result"]
         self.assertIn(
@@ -68,3 +70,37 @@ class TestDAP_console(lldbdap_testcase.DAPTestCaseBase):
         # currently selected frame.
 
         self.check_lldb_command("frame select", "frame #1", "frame 1 is selected")
+
+    @skipIfWindows
+    @skipIfRemote
+    def test_custom_escape_prefix(self):
+        program = self.getBuildArtifact("a.out")
+        self.build_and_launch(program, commandEscapePrefix="::")
+        source = "main.cpp"
+        breakpoint1_line = line_number(source, "// breakpoint 1")
+        breakpoint_ids = self.set_source_breakpoints(source, [breakpoint1_line])
+        self.continue_to_breakpoints(breakpoint_ids)
+
+        self.check_lldb_command(
+            "help",
+            "For more information on any command",
+            "Help can be invoked",
+            command_escape_prefix="::",
+        )
+
+    @skipIfWindows
+    @skipIfRemote
+    def test_empty_escape_prefix(self):
+        program = self.getBuildArtifact("a.out")
+        self.build_and_launch(program, commandEscapePrefix="")
+        source = "main.cpp"
+        breakpoint1_line = line_number(source, "// breakpoint 1")
+        breakpoint_ids = self.set_source_breakpoints(source, [breakpoint1_line])
+        self.continue_to_breakpoints(breakpoint_ids)
+
+        self.check_lldb_command(
+            "help",
+            "For more information on any command",
+            "Help can be invoked",
+            command_escape_prefix="",
+        )

lldb/tools/lldb-dap/DAP.cpp

@@ -382,9 +382,10 @@ llvm::json::Value DAP::CreateTopLevelScopes() {
 
 ExpressionContext DAP::DetectExpressionContext(lldb::SBFrame &frame,
                                                std::string &text) {
-  // Include ` as an escape hatch.
-  if (!text.empty() && text[0] == '`') {
-    text = text.substr(1);
+  // Include the escape hatch prefix.
+  if (!text.empty() &&
+      llvm::StringRef(text).starts_with(g_dap.command_escape_prefix)) {
+    text = text.substr(g_dap.command_escape_prefix.size());
     return ExpressionContext::Command;
   }
 
@@ -416,7 +417,9 @@ ExpressionContext DAP::DetectExpressionContext(lldb::SBFrame &frame,
         if (!auto_repl_mode_collision_warning) {
           llvm::errs() << "Variable expression '" << text
                        << "' is hiding an lldb command, prefix an expression "
-                          "with ` to ensure it runs as a lldb command.\n";
+                          "with '"
+                       << g_dap.command_escape_prefix
+                       << "' to ensure it runs as a lldb command.\n";
           auto_repl_mode_collision_warning = true;
         }
         return ExpressionContext::Variable;

lldb/tools/lldb-dap/DAP.h

@@ -188,6 +188,7 @@ struct DAP {
   ReplModeRequestHandler repl_mode_request_handler;
   ReplMode repl_mode;
   bool auto_repl_mode_collision_warning;
+  std::string command_escape_prefix = "`";
 
   DAP();
   ~DAP();

lldb/tools/lldb-dap/JSONUtils.cpp

@@ -46,15 +46,17 @@ llvm::StringRef GetAsString(const llvm::json::Value &value) {
 }
 
 // Gets a string from a JSON object using the key, or returns an empty string.
-llvm::StringRef GetString(const llvm::json::Object &obj, llvm::StringRef key) {
+llvm::StringRef GetString(const llvm::json::Object &obj, llvm::StringRef key,
+                          llvm::StringRef defaultValue) {
   if (std::optional<llvm::StringRef> value = obj.getString(key))
     return *value;
-  return llvm::StringRef();
+  return defaultValue;
 }
 
-llvm::StringRef GetString(const llvm::json::Object *obj, llvm::StringRef key) {
+llvm::StringRef GetString(const llvm::json::Object *obj, llvm::StringRef key,
+                          llvm::StringRef defaultValue) {
   if (obj == nullptr)
-    return llvm::StringRef();
+    return defaultValue;
   return GetString(*obj, key);
 }
 

lldb/tools/lldb-dap/JSONUtils.h

@@ -52,12 +52,17 @@ llvm::StringRef GetAsString(const llvm::json::Value &value);
 /// \param[in] key
 ///     The key to use when extracting the value
 ///
+/// \param[in] defaultValue
+///     The default value to return if the key is not present
+///
 /// \return
 ///     A llvm::StringRef that contains the string value for the
-///     specified \a key, or an empty string if there is no key that
+///     specified \a key, or the default value if there is no key that
 ///     matches or if the value is not a string.
-llvm::StringRef GetString(const llvm::json::Object &obj, llvm::StringRef key);
-llvm::StringRef GetString(const llvm::json::Object *obj, llvm::StringRef key);
+llvm::StringRef GetString(const llvm::json::Object &obj, llvm::StringRef key,
+                          llvm::StringRef defaultValue = {});
+llvm::StringRef GetString(const llvm::json::Object *obj, llvm::StringRef key,
+                          llvm::StringRef defaultValue = {});
 
 /// Extract the unsigned integer value for the specified key from
 /// the specified object.

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

@@ -651,6 +651,8 @@ void request_attach(const llvm::json::Object &request) {
       GetBoolean(arguments, "enableAutoVariableSummaries", false);
   g_dap.enable_synthetic_child_debugging =
       GetBoolean(arguments, "enableSyntheticChildDebugging", false);
+  g_dap.command_escape_prefix =
+      GetString(arguments, "commandEscapePrefix", "`");
 
   // This is a hack for loading DWARF in .o files on Mac where the .o files
   // in the debug map of the main executable have relative paths which require
@@ -1801,6 +1803,8 @@ void request_launch(const llvm::json::Object &request) {
       GetBoolean(arguments, "enableAutoVariableSummaries", false);
   g_dap.enable_synthetic_child_debugging =
       GetBoolean(arguments, "enableSyntheticChildDebugging", false);
+  g_dap.command_escape_prefix =
+      GetString(arguments, "commandEscapePrefix", "`");
 
   // This is a hack for loading DWARF in .o files on Mac where the .o files
   // in the debug map of the main executable have relative paths which require

lldb/tools/lldb-dap/package.json

@@ -250,6 +250,11 @@
 								"type": "boolean",
 								"description": "If a variable is displayed using a synthetic children, also display the actual contents of the variable at the end under a [raw] entry. This is useful when creating sythetic child plug-ins as it lets you see the actual contents of the variable.",
 								"default": false
+							},
+							"commandEscapePrefix": {
+								"type": "string",
+								"description": "The escape prefix to use for executing regular LLDB commands in the Debug Console, instead of printing variables. Defaults to a back-tick (`). If it's an empty string, then all expression in the Debug Console are treated as regular LLDB commands.",
+								"default": "`"
 							}
 						}
 					},
@@ -339,6 +344,11 @@
 								"type": "boolean",
 								"description": "If a variable is displayed using a synthetic children, also display the actual contents of the variable at the end under a [raw] entry. This is useful when creating sythetic child plug-ins as it lets you see the actual contents of the variable.",
 								"default": false
+							},
+							"commandEscapePrefix": {
+								"type": "string",
+								"description": "The escape prefix character to use for executing regular LLDB commands in the Debug Console, instead of printing variables. Defaults to a back-tick (`). If empty, then all expression in the Debug Console are treated as regular LLDB commands.",
+								"default": "`"
 							}
 						}
 					}