#!/usr/bin/env python

# -*- coding: utf-8 -*-

# java2python.mod.transform -> input AST transformer functions and constants.

#

# This module provides several transformation functions which are

# simple callables that modify AST nodes. These functions are not

# responsible for selecting nodes, only changing the node content.

# This gives us AST generation decoupled from AST traversal and

# modification.

#

# See the java2python.config.default and java2python.lang.selector modules to

# understand how and when selectors are associated with these callables.

import keyword

import types

from java2python.lang import tokens

def invalidPythonNames():

""" Creates a list of valid Java identifiers that are invalid in Python. """

ts = [getattr(types, n) for n in dir(types) if not n.startswith('_')]

ns = [t.__name__ for t in ts if isinstance(t, type)]

return ['None', 'True', 'False', ] + ns + keyword.kwlist

def keywordSafeIdent(node, config, invalid=invalidPythonNames()):

""" Validates and possibly renames a Java identifier. """

ident = node.token.text

if ident in invalid:

node.token.text = '%s_' % ident

def makeConst(v):

""" Returns a closure that indiscriminately changes node text to a value. """

def xform(node, config):

node.token.text = v

return xform

# Create transformers for mapping well-known Java idents into their

# Python counterparts:

null2None = makeConst('None')

false2False = makeConst('False')

true2True = makeConst('True')

def syntaxSafeFloatLiteral(node, config):

""" Ensures a Java float literal is a valid Python float literal. """

value = node.token.text

if value.startswith('.'):

value = '0' + value

if value.lower().endswith(('f', 'd')):

value = value[:-1]

elif value.endswith(('l', 'L')):

value = value[:-1] + 'L'

node.token.text = value

def lengthToLen(node, config):

""" Transforms expressions like 'value.length()' to 'len(value)'.

This method changes AST branches like this:

METHOD_CALL [start=45, stop=49]

DOT . [line=4, start=45, stop=47]

IDENT foo [line=4, start=45]

IDENT length [line=4, start=47]

ARGUMENT_LIST [line=4, start=48, stop=49]

Into branches like this:

IDENT len(foo) [line=4, start=45]

Notice that the resulting IDENT node text is invalid. We can't use a

METHOD_CALL token because those are always bound to a class or instance.

It would be best to add a new token type, and that option will be explored

if we run into this problem again.

"""

dot = node.parent

method = dot.parent

ident = dot.firstChildOfType(tokens.IDENT)

ident.token.text = 'len({})'.format(ident.text)

expr = method.parent

expr.children.remove(method)

expr.addChild(ident)

def typeSub(node, config):

""" Maps specific, well-known Java types to their Python counterparts.

See the `java2python.config.default` module for the default type

mapping and further discussion.

"""

ident = node.token.text

subs = config.last('typeSubs')

if ident in subs:

node.token.text = subs[ident]