Class Dispatcher

pythonwhat/State.py:276–315

class Dispatcher(DispatcherInterface):
    _context_cache = dict()

    def __init__(self, context_code=""):
        self._parser_cache = dict()
        context_ast = getattr(self._context_cache, context_code, None)
        if context_ast is None:
            context_ast = self._context_cache[context_code] = self.parse(context_code)[
                1
            ]
        self.context_mappings = self._getx(FunctionParser, "mappings", context_ast)

    def find(self, name, node, *args, **kwargs):
        return getattr(self, name)(node)

    def parse(self, code):
        res = asttokens.ASTTokens(code, parse=True)
        return res, res.tree

    # add methods for retrieving parser outputs --------------------------
    def _getx(self, Parser, ext_attr, tree):
        """getter for Parser outputs"""
        # return cached output if possible
        cache_key = Parser.__name__ + str(hash(tree))
        if self._parser_cache.get(cache_key):
            p = self._parser_cache[cache_key]
        else:
            # otherwise, run parser over tree
            p = Parser()
            # set mappings for parsers that inspect attribute access
            if ext_attr != "mappings" and Parser in [
                FunctionParser,
                ObjectAccessParser,
            ]:
                p.mappings = self.context_mappings.copy()
            # run parser
            p.visit(tree)
            # cache
            self._parser_cache[cache_key] = p
        return getattr(p, ext_attr)


# put a function on the dispatcher