Hi, I want to contribute in Ruby on Rails. Could someone point me to a beginner bug?
Do you mean you want to contribute to the development of Rails itself? If so then I suggest you first register with the rubyonrails-core list  and hang around there for a while to get a feel for things. Also (and perhaps easier) you could have a look at the open issues on any of the gems that you regularly use (devise perhaps, whatever gems you use) and try and fix them. Rails core code is not the easiest code to get to grips with.
Colin writes: “Rails core code is not the easiest code to get to grips with.”
What an understatement! I am actually an advanced mathematician with that training in precedence and exception and for years I have worked with ROR – in its history of versions. I’ll write with considerable confidence that it is extremely difficult to learn the nuance of ROR. (Watch Railscasts, and you want to abandon your profession. How/where does Ryan Bates learn this nuance?) I see 'authoritative" code examples here and I have no idea from whence they originated. As a starting point the documentation needs to be improved. Just as an obvious example, such frequent questions here are related to table/model associations.
The reason why Rails is so easy to work with (in practice), is because the framework’s source code is so complicated and intense. Or else the end-programmer would be required to a lot more themselves.
Hunter: Seriously you are joking…
Sorry, I meant it is easy in theory. In practice it is still difficult with, like you said, so many little nuances.