From ab01ae1620682ae214522d0be221685643fe6cf3 Mon Sep 17 00:00:00 2001
From: Stefan F <32997632+stefan301@users.noreply.github.com>
Date: Mon, 28 Sep 2020 18:28:47 +0200
Subject: [PATCH] flatc should output a warning, when an attribute is attached
 more than once (#6146)

* Added missing EndTable() call to VerifyObject()

VerifyObject called VerifyTableStart() but not EndTable(). This made Verifier::VerifyComplexity() increase depth_ with each table, not with the depth of tables.

https://groups.google.com/forum/#!topic/flatbuffers/OpxtW5UFAdg

* Added Check to VerifyAlignment

https://stackoverflow.com/questions/59376308/flatbuffers-verifier-returns-false-without-any-assertion-flatbuffers-debug-veri

* Add GetStringView (Convenience function to get string_view from a String returning an empty string_view on null pointer) like GetString, GetCstring

* flatc should warn, when an attribute is attached more than once.

flatc.exe -b duplicate.fbs
warning: duplicate.fbs(5, 36): warning: attribute already found: priority

duplicate.fbs:

namespace MyGame;

attribute "priority";

table Monster (priority:1, priority:2) {
}

root_type Monster;
---
 include/flatbuffers/flatbuffers.h | 2 +-
 src/idl_parser.cpp                | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/flatbuffers/flatbuffers.h b/include/flatbuffers/flatbuffers.h
index 799f6478a..279afd545 100644
--- a/include/flatbuffers/flatbuffers.h
+++ b/include/flatbuffers/flatbuffers.h
@@ -592,7 +592,7 @@ static inline const char *GetCstring(const String *str) {
 static inline flatbuffers::string_view GetStringView(const String *str) {
   return str ? str->string_view() : flatbuffers::string_view();
 }
-#endif  // FLATBUFFERS_HAS_STRING_VIEW
+#endif // FLATBUFFERS_HAS_STRING_VIEW
 
 // Allocator interface. This is flatbuffers-specific and meant only for
 // `vector_downward` usage.
diff --git a/src/idl_parser.cpp b/src/idl_parser.cpp
index cd81d822d..566482d21 100644
--- a/src/idl_parser.cpp
+++ b/src/idl_parser.cpp
@@ -1559,7 +1559,7 @@ CheckedError Parser::ParseMetaData(SymbolTable<Value> *attributes) {
                      name);
       NEXT();
       auto e = new Value();
-      attributes->Add(name, e);
+      if (attributes->Add(name, e)) Warning("attribute already found: " + name);
       if (Is(':')) {
         NEXT();
         ECHECK(ParseSingleValue(&name, *e, true));