#!/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]