[formatters] Draft Optional PR

lldb/examples/synthetic/gnu_libstdcpp.py

 from __future__ import division
 import re
 import lldb.formatters.Logger
 
 # C++ STL formatters for LLDB
 # These formatters are based upon the version of the GNU libstdc++
 # as it ships with Mac OS X 10.6.8 thru 10.8.0
 # You are encouraged to look at the STL implementation for your platform
 # before relying on these formatters to do the right thing for your setup
 
+class StdOptionalSynthProvider:
+    def __init__(self, valobj, dict):
+        self.valobj = valobj
+
+    def update(self):
+        try:
+            self.payload = self.valobj.GetChildMemberWithName('_M_payload')
+            self.engaged = self.payload.GetChildMemberWithName('_M_engaged')
+            self.payload_payload= self.payload.GetChildMemberWithName('_M_payload')
+        except:
+            pass
+        return False
+
+    def has_value(self):
+        logger = lldb.formatters.Logger.Logger()
+        try:
+            return self.engaged.GetValueAsUnsigned(0) == 1
+        except:
+            logger >> "Error determining engaged value"
+            return False
+
+    def num_children(self):
+        logger = lldb.formatters.Logger.Logger()
+        try:
+            num_children = 1 if self.has_value() else 0
+            return num_children
+        except:
+            logger >> "Error determining number of children"
+
+    def get_child_index(self, name):
+        try:
+            return int(name.lstrip('[').rstrip(']'))
+        except:
+            return -1
+
+    def get_child_at_index(self, index):
+        self.payload_value = self.payload_payload.GetChildMemberWithName("_M_value").GetValue()
+        if (self.has_value() == False):
+            pass
+        return self.payload_value
 
 class AbstractListSynthProvider:
     def __init__(self, valobj, dict, has_prev):
         '''
         :param valobj: The value object of the list
         :param dict: A dict with metadata provided by LLDB
         :param has_prev: Whether the list supports a 'prev' pointer besides a 'next' one
         '''

lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp

cpp_category_sp->GetRegexTypeSyntheticsContainer()->Add(
           stl_deref_flags,
           "lldb.formatters.cpp.gnu_libstdcpp.StdMapLikeSynthProvider")));
   cpp_category_sp->GetRegexTypeSyntheticsContainer()->Add(
       RegularExpression("^std::multimap<.+> >(( )?&)?$"),
       SyntheticChildrenSP(new ScriptedSyntheticChildren(
           stl_deref_flags,
           "lldb.formatters.cpp.gnu_libstdcpp.StdMapLikeSynthProvider")));
   cpp_category_sp->GetRegexTypeSyntheticsContainer()->Add(
+      RegularExpression("^std::optional<.+>(( )?&)?$"),
+      SyntheticChildrenSP(new ScriptedSyntheticChildren(
+          stl_synth_flags,
+          "lldb.formatters.cpp.gnu_libstdcpp.StdOptionalSynthProvider")));
+  cpp_category_sp->GetRegexTypeSyntheticsContainer()->Add(
       RegularExpression("^std::multiset<.+> >(( )?&)?$"),
       SyntheticChildrenSP(new ScriptedSyntheticChildren(
           stl_deref_flags,
           "lldb.formatters.cpp.gnu_libstdcpp.StdMapLikeSynthProvider")));
   cpp_category_sp->GetRegexTypeSyntheticsContainer()->Add(
       RegularExpression("^std::(__cxx11::)?list<.+>(( )?&)?$"),
       SyntheticChildrenSP(new ScriptedSyntheticChildren(
           stl_synth_flags,