[code-quality] Minimal example

[Claudiu Popa]

On Wed, Aug 17, 2016 at 10:37 PM, Patrik Iselind <patrik.mrx at gmail.com>
wrote:

> Thanks, i got it to work now.
>
> I have some feedback on the page you referred to.
>
> I was missing the implements line as well. This was not highlighted at
> all.
>
> Bullet two concerning priority. How checkers are ordered (internally?)
> doesn't help me to decide if i should set a negative priority close to zero
> or very far from zero in order for the checker to be first or at least
> among the first.
>
> I interpret this page as a resource you'd give programmers new to pylint
> checkers to get them started, awesome start! I think it would be really
> helpful if the page gave a overview of how the AST is buid and how i'm
> meant to access for example function variables in a function or the
> identifiers defined in a module. Where can i find a list of all the visit_*
> methods that i can use? I cannot find any class defining them all, are they
> dynamically called somehow?
>
> In examples directory referred to, looking at custom_raw.py. It implements
> process_module() instead of visit_*. What is the difference? When should i
> choose one over the other?
>
> Thanks a lot for your assistance in getting my first checker running.
>
> // Patrik
>
>
Hi Patrik,

These are all really good questions!

Would you mind adding your feedback over this issue
(https://github.com/PyCQA/pylint/issues/1071),
where I am tracking the documentation effort for writing a new checker?

In the mean time, some answers for your questions:

 - probably you shouldn't care that much about the priority,
   I don't know what its initial purpose was, so I presume it could
   be removed at some point. For what I care, each checker should
   not care about its order of execution, especially when considering
   calling them in a parallel environment.

- sure, we need to document these as well. Basically, any node
  from the builtin ast module should be available in pylint as well,
  under a visit_<node name> method.

- the process_module method is called whenever the checker is also
  a raw checker. The checkers can be AST checkers, operating on trees,
  token checkers, operating on tokens and raw checkers, operating on the
  file content itself. A checker can be all of these at the same
  time, if you declare the right __implements__. process_module is usually
  used when you need the entire content of the file for some reason.
  Of course, this can also be implemented with a visit_module()
   and getting the string representation of the module node, although
  we have some problems now with that, since we can't respect the
  invariant that ast.to_string() == file content.
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