[Lldb-commits] [lldb] [lldb-dap] Add feature to remember last non-empty expression. (PR #107485)

[via lldb-commits]

https://github.com/cmtice created https://github.com/llvm/llvm-project/pull/107485

Update lldb-dap so if the user just presses return, which sends an empty expression, it re-evaluates the most recent non-empty expression/command. Also udpated test to test this case.

>From 15541f354decf80586d590db9f9cb353be04b122 Mon Sep 17 00:00:00 2001
From: Caroline Tice <cmtice at google.com>
Date: Thu, 5 Sep 2024 15:51:35 -0700
Subject: [PATCH] [lldb-dap] Add feature to remember last non-empty expression.

Update lldb-dap so if the user just presses return, which sends an
empty expression, it re-evaluates the most recent non-empty
expression/command. Also udpated test to test this case.
---
 lldb/test/API/tools/lldb-dap/evaluate/TestDAP_evaluate.py | 3 +++
 lldb/tools/lldb-dap/lldb-dap.cpp                          | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/lldb/test/API/tools/lldb-dap/evaluate/TestDAP_evaluate.py b/lldb/test/API/tools/lldb-dap/evaluate/TestDAP_evaluate.py
index 29548a835c6919..9ed0fc564268a7 100644
--- a/lldb/test/API/tools/lldb-dap/evaluate/TestDAP_evaluate.py
+++ b/lldb/test/API/tools/lldb-dap/evaluate/TestDAP_evaluate.py
@@ -60,7 +60,10 @@ def run_test_evaluate_expressions(
 
         # Expressions at breakpoint 1, which is in main
         self.assertEvaluate("var1", "20")
+        # Empty expression should equate to the previous expression.
+        self.assertEvaluate("", "20")
         self.assertEvaluate("var2", "21")
+        self.assertEvaluate("", "21")
         self.assertEvaluate("static_int", "42")
         self.assertEvaluate("non_static_int", "43")
         self.assertEvaluate("struct1.foo", "15")
diff --git a/lldb/tools/lldb-dap/lldb-dap.cpp b/lldb/tools/lldb-dap/lldb-dap.cpp
index c5c4b09f15622b..a6a701dc2219fa 100644
--- a/lldb/tools/lldb-dap/lldb-dap.cpp
+++ b/lldb/tools/lldb-dap/lldb-dap.cpp
@@ -1363,6 +1363,14 @@ void request_evaluate(const llvm::json::Object &request) {
   lldb::SBFrame frame = g_dap.GetLLDBFrame(*arguments);
   std::string expression = GetString(arguments, "expression").str();
   llvm::StringRef context = GetString(arguments, "context");
+  static std::string last_nonempty_expression;
+
+  // Remember the last non-empty expression from the user, and use that if
+  // the current expression is empty (i.e. the user hit plain 'return').
+  if (!expression.empty())
+    last_nonempty_expression = expression;
+  else
+    expression = last_nonempty_expression;
 
   if (context == "repl" && g_dap.DetectExpressionContext(frame, expression) ==
                                ExpressionContext::Command) {