Extend synthetic children to produce synthetic values (as in, those that GetValueAsUnsigned(), GetValueAsCString() would return)

The way to do this is to write a synthetic child provider for your type, and have it vend the (optional) get_value function.
If get_value is defined, and it returns a valid SBValue, that SBValue's value (as in lldb_private::Value) will be used as the synthetic ValueObject's Value

The rationale for doing things this way is twofold:

- there are many possible ways to define a "value" (SBData, a Python number, ...) but SBValue seems general enough as a thing that stores a "value", so we just trade values that way and that keeps our currency trivial
- we could introduce a new level of layering (ValueObjectSyntheticValue), a new kind of formatter (synthetic value producer), but that would complicate the model (can I have a dynamic with no synthetic children but synthetic value? synthetic value with synthetic children but no dynamic?), and I really couldn't see much benefit to be reaped from this added complexity in the matrix
On the other hand, just defining a synthetic child provider with a get_value but returning no actual children is easy enough that it's not a significant road-block to adoption of this feature

Comes with a test case

llvm-svn: 219330

1 files changed, 30 insertions, 6 deletions

diff --git a/lldb/source/DataFormatters/ValueObjectPrinter.cpp b/lldb/source/DataFormatters/ValueObjectPrinter.cpp
index 3ce5051cc4e..126ff78c389 100644
--- a/lldb/source/DataFormatters/ValueObjectPrinter.cpp
+++ b/lldb/source/DataFormatters/ValueObjectPrinter.cpp
@@ -66,7 +66,7 @@ ValueObjectPrinter::Init (ValueObject* valobj,
 bool
 ValueObjectPrinter::PrintValueObject ()
 {
-    if (!GetDynamicValueIfNeeded () || m_valobj == nullptr)
+    if (!GetMostSpecializedValue () || m_valobj == nullptr)
         return false;
     
     if (ShouldPrintValueObject())
@@ -97,7 +97,7 @@ ValueObjectPrinter::PrintValueObject ()
 }
 
 bool
-ValueObjectPrinter::GetDynamicValueIfNeeded ()
+ValueObjectPrinter::GetMostSpecializedValue ()
 {
     if (m_valobj)
         return true;
@@ -134,6 +134,25 @@ ValueObjectPrinter::GetDynamicValueIfNeeded ()
             else
                 m_valobj = m_orig_valobj;
         }
+        
+        if (m_valobj->IsSynthetic())
+        {
+            if (options.m_use_synthetic == false)
+            {
+                ValueObject *non_synthetic = m_valobj->GetNonSyntheticValue().get();
+                if (non_synthetic)
+                    m_valobj = non_synthetic;
+            }
+        }
+        else
+        {
+            if (options.m_use_synthetic == true)
+            {
+                ValueObject *synthetic = m_valobj->GetSyntheticValue().get();
+                if (synthetic)
+                    m_valobj = synthetic;
+            }
+        }
     }
     m_clang_type = m_valobj->GetClangType();
     m_type_flags = m_clang_type.GetTypeInfo ();
@@ -442,8 +461,7 @@ ValueObjectPrinter::ShouldPrintChildren (bool is_failed_description,
 ValueObject*
 ValueObjectPrinter::GetValueObjectForChildrenGeneration ()
 {
-    ValueObjectSP synth_valobj_sp = m_valobj->GetSyntheticValue (options.m_use_synthetic);
-    return (synth_valobj_sp ? synth_valobj_sp.get() : m_valobj);
+    return m_valobj;
 }
 
 void
@@ -540,7 +558,13 @@ ValueObjectPrinter::PrintChildren (uint32_t curr_ptr_depth)
     {
         // Aggregate, no children...
         if (ShouldPrintValueObject())
-            m_stream->PutCString(" {}\n");
+        {
+            // if it has a synthetic value, then don't print {}, the synthetic children are probably only being used to vend a value
+            if (m_valobj->DoesProvideSyntheticValue())
+                m_stream->PutCString( "\n");
+            else
+                m_stream->PutCString(" {}\n");
+        }
     }
     else
     {
@@ -552,7 +576,7 @@ ValueObjectPrinter::PrintChildren (uint32_t curr_ptr_depth)
 bool
 ValueObjectPrinter::PrintChildrenOneLiner (bool hide_names)
 {
-    if (!GetDynamicValueIfNeeded () || m_valobj == nullptr)
+    if (!GetMostSpecializedValue () || m_valobj == nullptr)
         return false;
     
     ValueObject* synth_m_valobj = GetValueObjectForChildrenGeneration();