[lldb] Prevent mutation of CommandAlias::GetOptionArguments

[kastiglione]

Summary

Fix a mutation of CommandAlias::m_option_args_sp, which resulted in cases where
aliases would fail to run on second, and subsequent times.

For example, an alias such as:

command alias p1 p 1

When run the second time, the following error would be reported to the user:

error: expression failed to parse:
error: <user expression 1>:1:1: expression is not assignable
--  1
^   ~

To fix this, CommandAlias::Desugar now constructs options to a freshly constructed
vector, rather than by appending to the results of GetOptionArguments.

rdar://107770836

lldb/source/Interpreter/CommandAlias.cpp

 //===-- CommandAlias.cpp --------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Interpreter/CommandAlias.h"
 
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/ErrorHandling.h"
 
 #include "lldb/Interpreter/CommandInterpreter.h"
 #include "lldb/Interpreter/CommandObject.h"
 #include "lldb/Interpreter/CommandReturnObject.h"
 #include "lldb/Interpreter/Options.h"
 #include "lldb/Utility/StreamString.h"
 
std::pair<lldb::CommandObjectSP, OptionArgVectorSP> CommandAlias::Desugar() {
   auto underlying = GetUnderlyingCommand();
   if (!underlying)
     return {nullptr, nullptr};
 
   if (underlying->IsAlias()) {
     // FIXME: This doesn't work if the original alias fills a slot in the
     // underlying alias, since this just appends the two lists.
     auto desugared = ((CommandAlias *)underlying.get())->Desugar();
-    auto options = GetOptionArguments();
-    options->insert(options->begin(), desugared.second->begin(),
-                    desugared.second->end());
+    OptionArgVectorSP options = std::make_shared<OptionArgVector>();
+    llvm::append_range(*options, *desugared.second);
+    llvm::append_range(*options, *GetOptionArguments());
     return {desugared.first, options};
   }
 
   return {underlying, GetOptionArguments()};
 }
 
 // allow CommandAlias objects to provide their own help, but fallback to the
 // info for the underlying command if no customization has been provided

lldb/test/API/commands/command/nested_alias/TestNestedAlias.py

def test_nested_alias(self):
                 'Show variables for the current',
                 'stack frame.'],
             matching=True)
 
         # Check that aliases can be created for raw input commands.
         self.expect('command alias two expr -- 2')
         self.expect('command alias add_two two +')
         self.expect('add_two 3', patterns=[' = 5$'])
+        # Check that aliases to aliases to raw input commands work the second
+        # and subsequent times.
+        self.expect('add_two 3', patterns=[' = 5$'])
+        self.expect('add_two 3', patterns=[' = 5$'])