Add method QPDFValue::setChildDescription

libqpdf/QPDFObjectHandle.cc

@@ -36,6 +36,8 @@
 #include <stdexcept>
 #include <stdlib.h>
 
+using namespace std::literals;
+
 namespace
 {
     class TerminateParsing
@@ -813,13 +815,9 @@ QPDFObjectHandle::getArrayItem(int n)
             typeWarning("array", "returning null");
             QTC::TC("qpdf", "QPDFObjectHandle array null for non-array");
         }
-        QPDF* context = nullptr;
-        std::string description;
-        if (obj->getDescription(context, description)) {
-            result.setObjectDescription(
-                context,
-                description + " -> null returned from invalid array access");
-        }
+        static auto constexpr msg =
+            " -> null returned from invalid array access"sv;
+        result.obj->setChildDescription(obj, msg, "");
     }
     return result;
 }
@@ -1038,14 +1036,9 @@ QPDFObjectHandle::getKey(std::string const& key)
         typeWarning("dictionary", "returning null for attempted key retrieval");
         QTC::TC("qpdf", "QPDFObjectHandle dictionary null for getKey");
         result = newNull();
-        QPDF* qpdf = nullptr;
-        std::string description;
-        if (obj->getDescription(qpdf, description)) {
-            result.setObjectDescription(
-                qpdf,
-                (description + " -> null returned from getting key " + key +
-                 " from non-Dictionary"));
-        }
+        static auto constexpr msg =
+            " -> null returned from getting key $VD from non-Dictionary"sv;
+        result.obj->setChildDescription(obj, msg, key);
     }
     return result;
 }

libqpdf/QPDFValue.cc

@@ -17,6 +17,7 @@ QPDFValue::getDescription()
         switch (object_description->index()) {
         case 0:
             {
+                // Simple template string
                 auto description = std::get<0>(*object_description);
 
                 if (auto pos = description.find("$OG");
@@ -36,12 +37,27 @@ QPDFValue::getDescription()
             }
         case 1:
             {
+                // QPDF::JSONReactor generated description
                 auto j_descr = std::get<1>(*object_description);
                 return (
                     *j_descr.input +
                     (j_descr.object.empty() ? "" : ", " + j_descr.object) +
                     " at offset " + std::to_string(parsed_offset));
             }
+        case 2:
+            {
+                // Child object description
+                auto j_descr = std::get<2>(*object_description);
+                std::string result;
+                if (auto p = j_descr.parent.lock()) {
+                    result = p->getDescription();
+                }
+                result += j_descr.static_descr;
+                if (auto pos = result.find("$VD"); pos != std::string::npos) {
+                    result.replace(pos, 3, j_descr.var_descr);
+                }
+                return result;
+            }
         }
     } else if (og.isIndirect()) {
         return "object " + og.unparse(' ');

libqpdf/QPDF_Dictionary.cc

@@ -1,7 +1,10 @@
 #include <qpdf/QPDF_Dictionary.hh>
 
+#include <qpdf/QPDFObject_private.hh>
 #include <qpdf/QPDF_Name.hh>
 
+using namespace std::literals;
+
 QPDF_Dictionary::QPDF_Dictionary(
     std::map<std::string, QPDFObjectHandle> const& items) :
     QPDFValue(::ot_dictionary, "dictionary"),
@@ -98,10 +101,8 @@ QPDF_Dictionary::getKey(std::string const& key)
         return item->second;
     } else {
         auto null = QPDFObjectHandle::newNull();
-        if (qpdf != nullptr) {
-            null.setObjectDescription(
-                qpdf, getDescription() + " -> dictionary key " + key);
-        }
+        static auto constexpr msg = " -> dictionary key $VD"sv;
+        null.getObj()->setChildDescription(shared_from_this(), msg, key);
         return null;
     }
 }

libqpdf/qpdf/QPDFObject_private.hh

@@ -12,6 +12,7 @@
 #include <qpdf/Types.h>
 
 #include <string>
+#include <string_view>
 
 class QPDF;
 class QPDFObjectHandle;
@@ -76,6 +77,25 @@ class QPDFObject
     {
         return value->setDescription(qpdf, description, offset);
     }
+    void
+    setChildDescription(
+        std::shared_ptr<QPDFObject> parent,
+        std::string_view const& static_descr,
+        std::string var_descr)
+    {
+        auto qpdf = parent ? parent->value->qpdf : nullptr;
+        value->setChildDescription(
+            qpdf, parent->value, static_descr, var_descr);
+    }
+    void
+    setChildDescription(
+        std::shared_ptr<QPDFValue> parent,
+        std::string_view const& static_descr,
+        std::string var_descr)
+    {
+        auto qpdf = parent ? parent->qpdf : nullptr;
+        value->setChildDescription(qpdf, parent, static_descr, var_descr);
+    }
     bool
     getDescription(QPDF*& qpdf, std::string& description)
     {

libqpdf/qpdf/QPDFValue.hh

@@ -8,13 +8,14 @@
 #include <qpdf/Types.h>
 
 #include <string>
+#include <string_view>
 #include <variant>
 
 class QPDF;
 class QPDFObjectHandle;
 class QPDFObject;
 
-class QPDFValue
+class QPDFValue: public std::enable_shared_from_this<QPDFValue>
 {
     friend class QPDFObject;
 
@@ -38,7 +39,24 @@ class QPDFValue
         std::string object;
     };
 
-    using Description = std::variant<std::string, JSON_Descr>;
+    struct ChildDescr
+    {
+        ChildDescr(
+            std::shared_ptr<QPDFValue> parent,
+            std::string_view const& static_descr,
+            std::string var_descr) :
+            parent(parent),
+            static_descr(static_descr),
+            var_descr(var_descr)
+        {
+        }
+
+        std::weak_ptr<QPDFValue> parent;
+        std::string_view const& static_descr;
+        std::string var_descr;
+    };
+
+    using Description = std::variant<std::string, JSON_Descr, ChildDescr>;
 
     virtual void
     setDescription(
@@ -56,6 +74,17 @@ class QPDFValue
         qpdf = a_qpdf;
         og = a_og;
     }
+    void
+    setChildDescription(
+        QPDF* a_qpdf,
+        std::shared_ptr<QPDFValue> parent,
+        std::string_view const& static_descr,
+        std::string var_descr)
+    {
+        object_description = std::make_shared<Description>(
+            ChildDescr(parent, static_descr, var_descr));
+        qpdf = a_qpdf;
+    }
     std::string getDescription();
     bool
     hasDescription()