Implemented Json_writer_array & Json_writer_object subitems name presence control

.gitignore

@@ -10,8 +10,11 @@
 .ninja_*
 *.mri
 *.mri.tpl
+/.cproject
+/.project
 .gdb_history
 .vs/
+/.settings/
 errmsg.sys
 typescript
 _CPack_Packages

sql/my_json_writer.cc

@@ -260,6 +260,8 @@ void Json_writer::add_str(const String &str)
   add_str(str.ptr(), str.length());
 }
 
+thread_local std::vector<bool> Json_writer_struct::named_items_expectation;
+
 Json_writer_temp_disable::Json_writer_temp_disable(THD *thd_arg)
 {
   thd= thd_arg;

sql/my_json_writer.h

@@ -15,8 +15,12 @@
 
 #ifndef JSON_WRITER_INCLUDED
 #define JSON_WRITER_INCLUDED
+
 #include "my_base.h"
 #include "sql_select.h"
+
+#include <vector>
+
 class Opt_trace_stmt;
 class Opt_trace_context;
 class Json_writer;
@@ -308,6 +312,7 @@ class Json_value_helper
 /* A common base for Json_writer_object and Json_writer_array */
 class Json_writer_struct
 {
+  static thread_local std::vector<bool> named_items_expectation;
 protected:
   Json_writer* my_writer;
   Json_value_helper context;
@@ -317,16 +322,29 @@ class Json_writer_struct
   bool closed;
 
 public:
-  explicit Json_writer_struct(THD *thd)
+  explicit Json_writer_struct(THD *thd, bool expect_named_children)
   {
     my_writer= thd->opt_trace.get_current_json();
     context.init(my_writer);
     closed= false;
+    named_items_expectation.push_back(expect_named_children);
+  }
+
+  virtual ~Json_writer_struct()
+  {
+    named_items_expectation.pop_back();
   }
-  bool trace_started()
+
+  bool trace_started() const
   {
     return my_writer != 0;
   }
+
+  bool named_item_expected() const
+  {
+    return named_items_expectation.size() > 1
+        && *(named_items_expectation.rbegin() + 1);
+  }
 };
 
 
@@ -347,15 +365,17 @@ class Json_writer_object : public Json_writer_struct
   }
 public:
   explicit Json_writer_object(THD *thd)
-  : Json_writer_struct(thd)
+  : Json_writer_struct(thd, true)
   {
+    DBUG_ASSERT(!named_item_expected());
     if (unlikely(my_writer))
       my_writer->start_object();
   }
 
   explicit Json_writer_object(THD* thd, const char *str)
-    : Json_writer_struct(thd)
+  : Json_writer_struct(thd, true)
   {
+    DBUG_ASSERT(named_item_expected());
     if (unlikely(my_writer))
       my_writer->add_member(str).start_object();
   }
@@ -519,14 +539,18 @@ class Json_writer_object : public Json_writer_struct
 class Json_writer_array : public Json_writer_struct
 {
 public:
-  Json_writer_array(THD *thd): Json_writer_struct(thd)
+  Json_writer_array(THD *thd)
+  : Json_writer_struct(thd, false)
   {
+    DBUG_ASSERT(!named_item_expected());
     if (unlikely(my_writer))
       my_writer->start_array();
   }
 
-  Json_writer_array(THD *thd, const char *str) : Json_writer_struct(thd)
+  Json_writer_array(THD *thd, const char *str)
+  : Json_writer_struct(thd, false)
   {
+    DBUG_ASSERT(named_item_expected());
     if (unlikely(my_writer))
       my_writer->add_member(str).start_array();
   }