[lldb] Use current execution context in SBDebugger

Use `GetSelectedExecutionContext()` instead of
`GetCommandInterpreter().GetExecutionContext()` in
`SBDebugger::GetInternalVariableValue/SBDebugger::SetInternalVariable`. The
execution context in the command interpreter might be empty, if no commands has
been executed yet (it is updated only when handling commands or completions --
e.g.
https://github.com/llvm/llvm-project/blob/main/lldb/source/Interpreter/CommandInterpreter.cpp#L1855).

Reviewed By: teemperor

Differential Revision: https://reviews.llvm.org/D95761

Author: werat

lldb/source/API/SBDebugger.cpp

@@ -1278,8 +1278,7 @@ SBError SBDebugger::SetInternalVariable(const char *var_name, const char *value,
       ConstString(debugger_instance_name)));
   Status error;
   if (debugger_sp) {
-    ExecutionContext exe_ctx(
-        debugger_sp->GetCommandInterpreter().GetExecutionContext());
+    ExecutionContext exe_ctx(debugger_sp->GetSelectedExecutionContext());
     error = debugger_sp->SetPropertyValue(&exe_ctx, eVarSetOperationAssign,
                                           var_name, value);
   } else {
@@ -1303,8 +1302,7 @@ SBDebugger::GetInternalVariableValue(const char *var_name,
       ConstString(debugger_instance_name)));
   Status error;
   if (debugger_sp) {
-    ExecutionContext exe_ctx(
-        debugger_sp->GetCommandInterpreter().GetExecutionContext());
+    ExecutionContext exe_ctx(debugger_sp->GetSelectedExecutionContext());
     lldb::OptionValueSP value_sp(
         debugger_sp->GetPropertyValue(&exe_ctx, var_name, false, error));
     if (value_sp) {

lldb/test/API/python_api/debugger/TestDebuggerAPI.py

@@ -43,3 +43,35 @@ def test_debugger_delete_invalid_target(self):
         target = lldb.SBTarget()
         self.assertFalse(target.IsValid())
         self.dbg.DeleteTarget(target)
+
+    @add_test_categories(['pyapi'])
+    def test_debugger_internal_variables(self):
+        debugger_name = self.dbg.GetInstanceName()
+
+        # Set a variable and check it was written successfully.
+        error = lldb.SBDebugger.SetInternalVariable(
+            'target.prefer-dynamic-value', 'no-dynamic-values', debugger_name)
+        self.assertTrue(error.Success())
+        ret = lldb.SBDebugger.GetInternalVariableValue(
+            'target.prefer-dynamic-value', debugger_name)
+        self.assertEqual(ret.GetSize(), 1)
+        self.assertEqual(ret.GetStringAtIndex(0), 'no-dynamic-values')
+
+        # Set a variable with a different value.
+        error = lldb.SBDebugger.SetInternalVariable(
+            'target.prefer-dynamic-value', 'no-run-target', debugger_name)
+        self.assertTrue(error.Success())
+        ret = lldb.SBDebugger.GetInternalVariableValue(
+            'target.prefer-dynamic-value', debugger_name)
+        self.assertEqual(ret.GetSize(), 1)
+        self.assertEqual(ret.GetStringAtIndex(0), 'no-run-target')
+
+        # Try setting invalid value, check for error.
+        error = lldb.SBDebugger.SetInternalVariable(
+            'target.prefer-dynamic-value', 'dummy-value', debugger_name)
+        self.assertTrue(error.Fail())
+        # Check that the value didn't change.
+        ret = lldb.SBDebugger.GetInternalVariableValue(
+            'target.prefer-dynamic-value', debugger_name)
+        self.assertEqual(ret.GetSize(), 1)
+        self.assertEqual(ret.GetStringAtIndex(0), 'no-run-target')