Firebase.readEvent() returns "type" instead "put" while getting data from Firebase

[kptdobe]

PR for #364

Silly memory issue.

Running:

FirebaseObject event = Firebase.readEvent();
String var = event.getString("xyz");
String type = event.getString("type");

will always assign xyz to type even though the type in the JsonVariant is correct at the end of the readEvent method!
I am not a cpp expert but certainly something related with using pointers and memory allocation.
I do not know if this is the correct fix but at least it fixes the streaming issues...

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[kptdobe]

I signed it!

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[kptdobe]

@proppy Any chance you could review / merge this PR ?

[proppy]

@kptdobe sorry for the late reply, it seems that this change break the continuous integration (see the red cross near the travis logo).

Maybe using https://arduinojson.org/v5/api/jsonobject/set/ with the arduino String as an argument would be clearer?

[kptdobe]

I tried multiple versions of the code but no way to make the test pass.

set and = operator are calling the same internal methods which fail. Something is wrong with adding the type property to the JsonObject.

I really do not get why it runs fine with my local Arduino env and it does not in Travis. There is one thing different I cannot identify.

I also tried to update the Travis tests to ArduinoJson v5.13.2 (latest v5 - current runs v5.11.2) but not better.

[kotl]

Problem with Travis is that test environment uses different String definition and uses std::string underneath:
https://github.com/firebase/firebase-arduino/blob/master/contrib/test/WString.h

[kptdobe]

@kotl Thanks, this helped me to fix the tests!

Nasty issue. It seems that JsonObject#setdoes not like the std::string from the test environment. Copying the String into a char[] fixes the test issue without breaking the fix I made.

This repairs the Streaming and is test compliant! ;)

[kotl]

• Why not use type.c_str() directly?
• Please revert your changes to the test environment DEFS file -> we want to use ArduinoJson that was specified there before.

[kptdobe]

• type.c_str() is the source of the issue and causes the type to always be equal to "type": it returns a pointer while the set method does not copy internally the string and use the pointer as is. And later, the memory at this location does not change anymore, type never get updated anymore. That's why the streaming does not work. I am not a cpp expert, there might be a better explanation though...
• if you talk about the changes I made to the .travis.yml file, I reverted them already, the PR is only about one file.

[kotl]

• needs: delete [] cstr;
• change strcpy to strncpy

[kotl]

thank you very much for doing this.

[proppy]

wouldn't that leak?

[proppy]

ah missed the delete, I was thinking it might not be safe to delete if JsonVariant keep a ref on it.
But set() documentation seems to imply that it make a copy if you pass a char* https://arduinojson.org/v5/api/jsonobject/set/.