[lldb-dap] Correct auto-completion based on ReplMode and escape char (#110784)

This commit improves the auto-completion in the Debug Console provided
by VS-Code.

So far, we were always suggesting completions for both LLDB commands and
for variables / expressions, even if the heuristic already determined
how the given string will be executed, e.g., because the user explicitly
typed the escape prefix. Furthermore, auto-completion after the escape
character was broken, since the offsets were not adjusted correctly.
With this commit we now correctly take this into account.

Even with this commit, auto-completion does not always work reliably:

* VS Code only requests auto-completion after typing the first
alphabetic character, but not after punctuation characters. This means
that no completions are provided after typing "`"
* LLDB does not provide autocompletions if a string is an exact match.
This means if a user types `l` (which is a valid command), LLDB will not
provide "language" and "log" as potential completions. Even worse, VS
Code caches the completion and does client-side filtering. Hence, even
after typing `la`, no auto-completion for "language" is shown in the UI.

Those issues might be fixed in follow-up commits. Also with those known
issues, the experience is already much better with this commit.

Furthermore, I updated the README since I noticed that it was slightly
inaccurate.

1 files changed, 1 insertions, 1 deletions

diff --git a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py
index 449af1b..1d5e6e0 100644
--- a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py
+++ b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py
@@ -1006,7 +1006,7 @@ class DebugCommunication(object):
         return response
 
     def request_completions(self, text, frameId=None):
-        args_dict = {"text": text, "column": len(text)}
+        args_dict = {"text": text, "column": len(text) + 1}
         if frameId:
             args_dict["frameId"] = frameId
         command_dict = {