Merge pull request #8350 from Michael137/bugfix/lldb-tab-completion-crash-to-20230725

[cherry-pick][stable/20230725] [LLDB] Fix crash when using tab completion on class variables

We weren't checking to see if the partial_path was empty before adding
completions and this led to crashes when the class object and a variable
both start with the same substring.

(cherry picked from commit de55188)

Author: Michael137

lldb/source/Symbol/Variable.cpp

@@ -509,15 +509,17 @@ static void PrivateAutoCompleteMembers(
       CompilerType member_compiler_type = compiler_type.GetFieldAtIndex(
           i, member_name, nullptr, nullptr, nullptr);
 
-      if (partial_member_name.empty() ||
-          llvm::StringRef(member_name).startswith(partial_member_name)) {
+      if (partial_member_name.empty()) {
+        request.AddCompletion((prefix_path + member_name).str());
+      } else if (llvm::StringRef(member_name)
+                     .startswith(partial_member_name)) {
         if (member_name == partial_member_name) {
           PrivateAutoComplete(
               frame, partial_path,
               prefix_path + member_name, // Anything that has been resolved
                                          // already will be in here
               member_compiler_type.GetCanonicalType(), request);
-        } else {
+        } else if (partial_path.empty()) {
           request.AddCompletion((prefix_path + member_name).str());
         }
       }

lldb/test/API/functionalities/completion/TestCompletion.py

@@ -60,10 +60,12 @@ def test_dwim_print(self):
 
     def do_test_variable_completion(self, command):
         self.complete_from_to(f"{command} fo", f"{command} fooo")
-        self.complete_from_to(f"{command} fooo.", f"{command} fooo.")
+        self.complete_from_to(f"{command} fooo.", f"{command} fooo.t")
+        self.complete_from_to(f"{command} fooo.t.", f"{command} fooo.t.x")
         self.complete_from_to(f"{command} fooo.dd", f"{command} fooo.dd")
 
-        self.complete_from_to(f"{command} ptr_fooo->", f"{command} ptr_fooo->")
+        self.complete_from_to(f"{command} ptr_fooo->", f"{command} ptr_fooo->t")
+        self.complete_from_to(f"{command} ptr_fooo->t.", f"{command} ptr_fooo->t.x")
         self.complete_from_to(f"{command} ptr_fooo->dd", f"{command} ptr_fooo->dd")
 
         self.complete_from_to(f"{command} cont", f"{command} container")

lldb/test/API/functionalities/completion/main.cpp

@@ -1,12 +1,17 @@
 #include <iostream>
 
+class Baz {
+public:
+  int x;
+};
+
 class Foo
 {
 public:
-    int Bar(int x, int y)
-    {
-        return x + y;
-    }
+  Baz t;
+  int temp;
+
+  int Bar(int x, int y) { return x + y; }
 };
 
 namespace { int Quux (void) { return 0; } }