[Lldb-commits] [lldb] [LLDB]Provide clearer error message for invalid commands. (PR #111891)

[Pavel Labath via lldb-commits]

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@@ -194,28 +194,54 @@ void CommandObjectMultiword::Execute(const char *args_string,
 
   std::string error_msg;
   const size_t num_subcmd_matches = matches.GetSize();
-  if (num_subcmd_matches > 0)
+  if (num_subcmd_matches > 0) {
     error_msg.assign("ambiguous command ");
-  else
-    error_msg.assign("invalid command ");
-
-  error_msg.append("'");
-  error_msg.append(std::string(GetCommandName()));
-  error_msg.append(" ");
-  error_msg.append(std::string(sub_command));
-  error_msg.append("'.");
+    error_msg.append("'");
+    error_msg.append(std::string(GetCommandName()));
+    error_msg.append(" ");
+    error_msg.append(std::string(sub_command));
+    error_msg.append("'.");
 
-  if (num_subcmd_matches > 0) {
     error_msg.append(" Possible completions:");
     for (const std::string &match : matches) {
       error_msg.append("\n\t");
       error_msg.append(match);
     }
+  } else {
+    // Try to offer some alternatives to help correct the command.
+    error_msg.assign(
+        llvm::Twine("'" + sub_command + "' is not a valid subcommand of \"" +
+                    GetCommandName() + "\"." + GetSubcommandsHintText() +
+                    " Use \"help " + GetCommandName() + "\" to find out more.")
+            .str());
   }
   error_msg.append("\n");
   result.AppendRawError(error_msg.c_str());
 }
 
+std::string CommandObjectMultiword::GetSubcommandsHintText() {
+  if (m_subcommand_dict.empty())
+    return "";
+  const size_t maxCount = 5;
+  size_t i = 0;
+  std::string buffer = " Valid subcommand";
+  buffer.append(m_subcommand_dict.size() > 1 ? "s are:" : "is");
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labath wrote:

You're right. I missed the `empty()` check at the beginning of the function.

https://github.com/llvm/llvm-project/pull/111891