Refine comments and documentation for ProductSearch type="exists"

Author: robmen

src/burn/engine/search.cpp

@@ -1252,7 +1252,8 @@ static HRESULT MsiProductSearch(
     hr = BVariantChangeType(&value, type);
     ExitOnFailure(hr, "Failed to change value type.");
 
-    // Alter value here after value has changed to numberic type.
+    // When testing if a product exists, replace the value with a numeric "true" or "false"
+    // based on the calculated install state.
     if (BURN_MSI_PRODUCT_SEARCH_TYPE_EXISTS == pSearch->MsiProductSearch.Type)
     {
         value.llValue = (value.llValue == INSTALLSTATE_ABSENT) ? 0 : 1;

src/xsd/util.xsd

@@ -1346,7 +1346,10 @@
             </xs:enumeration>
             <xs:enumeration value="exists">
               <xs:annotation>
-                <xs:documentation>Saves true if a matching product entry is found; false otherwise.</xs:documentation>
+                <xs:documentation>
+                  [WiX v7 and later]
+                  Saves true if a matching product entry is found (non-absent); false otherwise.
+                </xs:documentation>
               </xs:annotation>
             </xs:enumeration>
           </xs:restriction>