Handle aliasing a non-top-level command.

This didn't work previously because we had to check whether the incoming
command was an alias command, but if it wasn't we still used the result
of that lookup - which was by the command's node name.  That fails for
non-top-level commands.  In this case, the resolution is pretty simple since
we already have the node's CommandObject, so all we needed to do was turn
it into a shared pointer, for which I added enable_shared_from_this to the
CommandObject.

Differential Revision: https://reviews.llvm.org/D137662

Author: jimingham

lldb/include/lldb/Interpreter/CommandObject.h

@@ -10,6 +10,7 @@
 #define LLDB_INTERPRETER_COMMANDOBJECT_H
 
 #include <map>
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -64,7 +65,7 @@ size_t FindLongestCommandWord(std::map<std::string, ValueType> &dict) {
   return max_len;
 }
 
-class CommandObject {
+class CommandObject : public std::enable_shared_from_this<CommandObject> {
 public:
   typedef llvm::StringRef(ArgumentHelpCallbackFunction)();
 

lldb/source/Commands/CommandObjectCommands.cpp

@@ -485,29 +485,31 @@ rather than using a positional placeholder:"
         OptionArgVectorSP(new OptionArgVector);
 
     const bool include_aliases = true;
-    if (CommandObjectSP cmd_obj_sp = m_interpreter.GetCommandSPExact(
-            cmd_obj.GetCommandName(), include_aliases)) {
-      if (m_interpreter.AliasExists(alias_command) ||
-          m_interpreter.UserCommandExists(alias_command)) {
-        result.AppendWarningWithFormat(
-            "Overwriting existing definition for '%s'.\n",
-            alias_command.str().c_str());
-      }
-      if (CommandAlias *alias = m_interpreter.AddAlias(
-              alias_command, cmd_obj_sp, raw_command_string)) {
-        if (m_command_options.m_help.OptionWasSet())
-          alias->SetHelp(m_command_options.m_help.GetCurrentValue());
-        if (m_command_options.m_long_help.OptionWasSet())
-          alias->SetHelpLong(m_command_options.m_long_help.GetCurrentValue());
-        result.SetStatus(eReturnStatusSuccessFinishNoResult);
-      } else {
-        result.AppendError("Unable to create requested alias.\n");
-      }
+    // Look up the command using command's name first.  This is to resolve
+    // aliases when you are making nested aliases.  But if you don't find
+    // it that way, then it wasn't an alias and we can just use the object
+    // we were passed in.
+    CommandObjectSP cmd_obj_sp = m_interpreter.GetCommandSPExact(
+            cmd_obj.GetCommandName(), include_aliases);
+    if (!cmd_obj_sp)
+      cmd_obj_sp = cmd_obj.shared_from_this();
 
+    if (m_interpreter.AliasExists(alias_command) ||
+        m_interpreter.UserCommandExists(alias_command)) {
+      result.AppendWarningWithFormat(
+          "Overwriting existing definition for '%s'.\n",
+          alias_command.str().c_str());
+    }
+    if (CommandAlias *alias = m_interpreter.AddAlias(
+            alias_command, cmd_obj_sp, raw_command_string)) {
+      if (m_command_options.m_help.OptionWasSet())
+        alias->SetHelp(m_command_options.m_help.GetCurrentValue());
+      if (m_command_options.m_long_help.OptionWasSet())
+        alias->SetHelpLong(m_command_options.m_long_help.GetCurrentValue());
+      result.SetStatus(eReturnStatusSuccessFinishNoResult);
     } else {
       result.AppendError("Unable to create requested alias.\n");
     }
-
     return result.Succeeded();
   }
 

lldb/test/API/commands/command/container/TestContainerCommands.py

@@ -55,6 +55,12 @@ def container_add(self):
         self.expect("test-multi test-multi-sub welcome friend", "Test command works",
                     substrs=["Hello friend, welcome to LLDB"])
 
+        # Make sure we can make an alias to this:
+        self.runCmd("command alias my-welcome test-multi test-multi-sub welcome", "We can make an alias to multi-word")
+        self.expect("my-welcome friend", "Test command works",
+                    substrs=["Hello friend, welcome to LLDB"])
+        self.runCmd("command unalias my-welcome")
+        
         # Make sure overwriting works on the leaf command.  First using the
         # explicit option so we should not be able to remove extant commands by default: