[lldb] Add flag to "settings show" to include default values (#153233)

Adds a `--defaults`/`-d` flag to `settings show`. This mode will _optionally_ show a
setting's default value. In other words, this does not always print a default value for
every setting.

A default value is not shown when the current value _is_ the default.

Note: some setting types do not print empty or invalid values. For these setting types,
if the default value is empty or invalid, the same elision logic is applied to printing
the default value.

1 files changed, 8 insertions, 1 deletions

diff --git a/lldb/source/Interpreter/OptionValueLanguage.cpp b/lldb/source/Interpreter/OptionValueLanguage.cpp
index 0fdaacb02594..bb28dc8debe6 100644
--- a/lldb/source/Interpreter/OptionValueLanguage.cpp
+++ b/lldb/source/Interpreter/OptionValueLanguage.cpp
@@ -9,8 +9,9 @@
 #include "lldb/Interpreter/OptionValueLanguage.h"
 
 #include "lldb/DataFormatters/FormatManager.h"
-#include "lldb/Target/Language.h"
+#include "lldb/Interpreter/OptionValue.h"
 #include "lldb/Symbol/TypeSystem.h"
+#include "lldb/Target/Language.h"
 #include "lldb/Utility/Args.h"
 #include "lldb/Utility/Stream.h"
 
@@ -26,6 +27,12 @@ void OptionValueLanguage::DumpValue(const ExecutionContext *exe_ctx,
       strm.PutCString(" = ");
     if (m_current_value != eLanguageTypeUnknown)
       strm.PutCString(Language::GetNameForLanguageType(m_current_value));
+    if (dump_mask & eDumpOptionDefaultValue &&
+        m_current_value != m_default_value &&
+        m_default_value != eLanguageTypeUnknown) {
+      DefaultValueFormat label(strm);
+      strm.PutCString(Language::GetNameForLanguageType(m_default_value));
+    }
   }
 }