Source code for jasy.script.optimize.LocalVariables

#
# Jasy - Web Tooling Framework
# Copyright 2010-2012 Zynga Inc.
# Copyright 2013-2014 Sebastian Werner
#

import string
import jasy.script.tokenize.Lang



#
# Public API
#


class Error(Exception):
    def __init__(self, name, line):
        self.__name = name
        self.__line = line

    def __str__(self):
        return "Unallowed private field access to %s at line %s!" % (self.__name, self.__line)


def optimize(node):
    """
    Node to optimize with the global variables to ignore as names
    """

    blocked = set(node.scope.shared.keys())
    blocked.update(node.scope.modified)

    __patch(node, blocked)



#
# Implementation
#

def __baseEncode(num, alphabet=string.ascii_letters):
    if (num == 0):
        return alphabet[0]
    arr = []
    base = len(alphabet)
    while num:
        rem = num % base
        num = num // base
        arr.append(alphabet[rem])
    arr.reverse()
    return "".join(arr)


def __patch(node, blocked=None, enable=False, translate=None):
    # Start with first level scopes (global scope should not be affected)
    if node.type == "script" and hasattr(node, "parent"):
        enable = True


    #
    # GENERATE TRANSLATION TABLE
    #
    if enable:
        scope = getattr(node, "scope", None)

        if scope:
            declared = scope.declared
            params = scope.params

            if declared or params:
                usedRepl = set()

                if not translate:
                    translate = {}
                else:
                    # copy only the interesting ones from the shared set
                    newTranslate = {}

                    for name in scope.shared:
                        if name in translate:
                            newTranslate[name] = translate[name]
                            usedRepl.add(translate[name])
                    translate = newTranslate

                # Merge in usage data into declaration map to have
                # the possibilities to sort translation priority to
                # the usage number. Pretty cool.

                names = set()
                if params:
                    names.update(params)
                if declared:
                    names.update(declared)

                # We have to sort the set() before to support both Python 3.2 and
                # Python 3.3 with identical results.
                namesSorted = list(reversed(sorted(sorted(names), key=lambda x: scope.accessed[x] if x in scope.accessed else 0)))

                # Extend translation map by new replacements for locally
                # declared variables. Automatically ignores keywords. Only
                # blocks usage of replacements where the original variable from
                # outer scope is used. This way variable names may be re-used more
                # often than in the original code.
                pos = 0
                for name in namesSorted:
                    while True:
                        repl = __baseEncode(pos)
                        pos += 1
                        if not repl in usedRepl and not repl in jasy.script.tokenize.Lang.keywords and not repl in blocked:
                            break

                    # print("Translate: %s => %s" % (name, repl))
                    translate[name] = repl


    #
    # APPLY TRANSLATION
    #
    if translate:
        # Update param names in outer function block
        if node.type == "script" and hasattr(node, "parent"):
            function = node.parent
            if function.type == "function" and hasattr(function, "params"):
                for identifier in function.params:
                    if identifier.value in translate:
                        identifier.value = translate[identifier.value]

        # Update names of exception objects
        elif node.type == "exception" and node.value in translate:
            node.value = translate[node.value]

        # Update function name
        elif node.type == "function" and hasattr(node, "name") and node.name in translate:
            node.name = translate[node.name]

        # Update identifiers
        elif node.type == "identifier":
            # Ignore param blocks from inner functions
            if node.parent.type == "list" and getattr(node.parent, "rel", None) == "params":
                pass

            # Ignore keyword in property initialization names
            elif node.parent.type == "property_init" and node.parent[0] == node:
                pass

            # Update all identifiers which are
            # a) not part of a dot operator
            # b) first in a dot operator
            elif node.parent.type != "dot" or node.parent.index(node) == 0:
                if node.value in translate:
                    node.value = translate[node.value]

        # Update declarations (as part of a var statement)
        elif node.type == "declaration":
            varName = getattr(node, "name", None)
            if varName != None:
                if varName in translate:
                    node.name = varName = translate[varName]
            else:
                # JS 1.7 Destructing Expression
                for identifier in node.names:
                    if identifier.value in translate:
                        identifier.value = translate[identifier.value]


    #
    # PROCESS CHILDREN
    #
    for child in node:
        # None children are allowed sometimes e.g. during array_init like [1,2,,,7,8]
        if child != None:
            __patch(child, blocked, enable, translate)