C++ AVRO-3601 broke custom non-string attributes

[John Dickson]

AVRO-3601 fixed the install issue, but any schema with non-string custom
attributes now fails to compile with an exception.
For example the following IDL generates a schema that cannot be used in C++
1.11.2, while it worked in earlier versions:

protocol A {
record Test {
  string @extra({"custom1":"value", "custom2": true}) f1;
}
}

schema:
{
  "type": "record",
  "name": "Test",
  "fields": [ {
    "name": "f1",
    "type": "string",
    "extra": {
      "custom1": "value",
      "custom2": true
    }
  } ]
}

The following patch allows the schema to compile while maintaining the
current behavior for string attributes, but leaves it ambiguous if the
content of the string is also a valid JSON value.


~/projects/libraries/avro$ git diff lang/c++/impl/Compiler.cc
lang/c++/test/SchemaTests.cc
diff --git a/lang/c++/impl/Compiler.cc b/lang/c++/impl/Compiler.cc
index 383798c4d..e5990e6e2 100644
--- a/lang/c++/impl/Compiler.cc
+++ b/lang/c++/impl/Compiler.cc
@@ -275,7 +275,11 @@ static void getCustomAttributes(const Object& m,
CustomAttributes &customAttribu
   const std::unordered_set<std::string>& kKnownFields = getKnownFields();
   for (const auto &entry : m) {
     if (kKnownFields.find(entry.first) == kKnownFields.end()) {
-      customAttributes.addAttribute(entry.first,
entry.second.stringValue());
+      if (entry.second.type() == json::EntityType::String) {
+        customAttributes.addAttribute(entry.first,
entry.second.stringValue());
+      } else {
+        customAttributes.addAttribute(entry.first,
entry.second.toString());
+      }
     }
   }
 }
diff --git a/lang/c++/test/SchemaTests.cc b/lang/c++/test/SchemaTests.cc
index d73b759cf..ee1014510 100755
--- a/lang/c++/test/SchemaTests.cc
+++ b/lang/c++/test/SchemaTests.cc
@@ -112,6 +112,8 @@ const char *basicSchemas[] = {
     "{\"type\": \"record\",\"name\": \"Test\",\"fields\": "
         "[{\"name\": \"f1\",\"type\": \"long\","
         "\"extra field1\": \"1\",\"extra field2\": \"2\"}]}"
+    ,R"({"type": "record","name": "Test","fields":
+        [{"name": "f1","type": "string", "extra": {"custom1":
"value","custom2": true }}]})"
 };

 const char *basicSchemaErrors[] = {


To get rid of the ambiguity at the cost of altering the existing behavior,
you could just change Compiler.cc line 278 from:
customAttributes.addAttribute(entry.first, entry.second.stringValue());
to:
customAttributes.addAttribute(entry.first, entry.second.toString());

Thanks,
John