File: as_string.py

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# copyright 2003-2013 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of logilab-astng.
#
# logilab-astng is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation, either version 2.1 of the License, or (at your
# option) any later version.
#
# logilab-astng is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
# for more details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with logilab-astng. If not, see <http://www.gnu.org/licenses/>.
"""This module renders ASTNG nodes as string:

* :func:`to_code` function return equivalent (hopefuly valid) python string

* :func:`dump` function return an internal representation of nodes found
  in the tree, useful for debugging or understanding the tree structure
"""

import sys

INDENT = '    ' # 4 spaces ; keep indentation variable


def dump(node, ids=False):
    """print a nice astng tree representation.

    :param ids: if true, we also print the ids (usefull for debugging)
    """
    result = []
    _repr_tree(node, result, ids=ids)
    return "\n".join(result)

def _repr_tree(node, result, indent='', _done=None, ids=False):
    """built a tree representation of a node as a list of lines"""
    if _done is None:
        _done = set()
    if not hasattr(node, '_astng_fields'): # not a astng node
        return
    if node in _done:
        result.append( indent + 'loop in tree: %s' % node )
        return
    _done.add(node)
    node_str = str(node)
    if ids:
        node_str += '  . \t%x' % id(node)
    result.append( indent + node_str )
    indent += INDENT
    for field in node._astng_fields:
        value = getattr(node, field)
        if isinstance(value, (list, tuple) ):
            result.append(  indent + field + " = [" )
            for child in value:
                if isinstance(child, (list, tuple) ):
                    # special case for Dict # FIXME
                    _repr_tree(child[0], result, indent, _done, ids)
                    _repr_tree(child[1], result, indent, _done, ids)
                    result.append(indent + ',')
                else:
                    _repr_tree(child, result, indent, _done, ids)
            result.append(  indent + "]" )
        else:
            result.append(  indent + field + " = " )
            _repr_tree(value, result, indent, _done, ids)


class AsStringVisitor(object):
    """Visitor to render an ASTNG node as a valid python code string"""

    def __call__(self, node):
        """Makes this visitor behave as a simple function"""
        return node.accept(self)

    def _stmt_list(self, stmts):
        """return a list of nodes to string"""
        stmts = '\n'.join([nstr for nstr in [n.accept(self) for n in stmts] if nstr])
        return INDENT + stmts.replace('\n', '\n'+INDENT)


    ## visit_<node> methods ###########################################

    def visit_arguments(self, node):
        """return an astng.Function node as string"""
        return node.format_args()

    def visit_assattr(self, node):
        """return an astng.AssAttr node as string"""
        return self.visit_getattr(node)

    def visit_assert(self, node):
        """return an astng.Assert node as string"""
        if node.fail:
            return 'assert %s, %s' % (node.test.accept(self),
                                        node.fail.accept(self))
        return 'assert %s' % node.test.accept(self)

    def visit_assname(self, node):
        """return an astng.AssName node as string"""
        return node.name

    def visit_assign(self, node):
        """return an astng.Assign node as string"""
        lhs = ' = '.join([n.accept(self) for n in node.targets])
        return '%s = %s' % (lhs, node.value.accept(self))

    def visit_augassign(self, node):
        """return an astng.AugAssign node as string"""
        return '%s %s %s' % (node.target.accept(self), node.op, node.value.accept(self))

    def visit_backquote(self, node):
        """return an astng.Backquote node as string"""
        return '`%s`' % node.value.accept(self)

    def visit_binop(self, node):
        """return an astng.BinOp node as string"""
        return '(%s) %s (%s)' % (node.left.accept(self), node.op, node.right.accept(self))

    def visit_boolop(self, node):
        """return an astng.BoolOp node as string"""
        return (' %s ' % node.op).join(['(%s)' % n.accept(self)
                                            for n in node.values])

    def visit_break(self, node):
        """return an astng.Break node as string"""
        return 'break'

    def visit_callfunc(self, node):
        """return an astng.CallFunc node as string"""
        expr_str = node.func.accept(self)
        args = [arg.accept(self) for arg in node.args]
        if node.starargs:
            args.append( '*' + node.starargs.accept(self))
        if node.kwargs:
            args.append( '**' + node.kwargs.accept(self))
        return '%s(%s)' % (expr_str, ', '.join(args))

    def visit_class(self, node):
        """return an astng.Class node as string"""
        decorate = node.decorators and node.decorators.accept(self)  or ''
        bases =  ', '.join([n.accept(self) for n in node.bases])
        bases = bases and '(%s)' % bases or ''
        docs = node.doc and '\n%s"""%s"""' % (INDENT, node.doc) or ''
        return '\n\n%sclass %s%s:%s\n%s\n' % (decorate, node.name, bases, docs,
                                            self._stmt_list( node.body))

    def visit_compare(self, node):
        """return an astng.Compare node as string"""
        rhs_str = ' '.join(['%s %s' % (op, expr.accept(self))
                            for op, expr in node.ops])
        return '%s %s' % (node.left.accept(self), rhs_str)

    def visit_comprehension(self, node):
        """return an astng.Comprehension node as string"""
        ifs = ''.join([ ' if %s' % n.accept(self) for n in node.ifs])
        return 'for %s in %s%s' % (node.target.accept(self),
                                    node.iter.accept(self), ifs )

    def visit_const(self, node):
        """return an astng.Const node as string"""
        return repr(node.value)

    def visit_continue(self, node):
        """return an astng.Continue node as string"""
        return 'continue'

    def visit_delete(self, node): # XXX check if correct
        """return an astng.Delete node as string"""
        return 'del %s' % ', '.join([child.accept(self)
                                for child in node.targets])

    def visit_delattr(self, node):
        """return an astng.DelAttr node as string"""
        return self.visit_getattr(node)

    def visit_delname(self, node):
        """return an astng.DelName node as string"""
        return node.name

    def visit_decorators(self, node):
        """return an astng.Decorators node as string"""
        return '@%s\n' % '\n@'.join([item.accept(self) for item in node.nodes])

    def visit_dict(self, node):
        """return an astng.Dict node as string"""
        return '{%s}' % ', '.join(['%s: %s' % (key.accept(self),
                            value.accept(self)) for key, value in node.items])

    def visit_dictcomp(self, node):
        """return an astng.DictComp node as string"""
        return '{%s: %s %s}' % (node.key.accept(self), node.value.accept(self),
                ' '.join([n.accept(self) for n in node.generators]))

    def visit_discard(self, node):
        """return an astng.Discard node as string"""
        return node.value.accept(self)

    def visit_emptynode(self, node):
        """dummy method for visiting an Empty node"""
        return ''

    def visit_excepthandler(self, node):
        if node.type:
            if node.name:
                excs = 'except %s, %s' % (node.type.accept(self),
                                        node.name.accept(self))
            else:
                excs = 'except %s' % node.type.accept(self)
        else:
            excs = 'except'
        return '%s:\n%s' % (excs, self._stmt_list(node.body))

    def visit_ellipsis(self, node):
        """return an astng.Ellipsis node as string"""
        return '...'

    def visit_empty(self, node):
        """return an Empty node as string"""
        return ''

    def visit_exec(self, node):
        """return an astng.Exec node as string"""
        if node.locals:
            return 'exec %s in %s, %s' % (node.expr.accept(self),
                                          node.locals.accept(self),
                                          node.globals.accept(self))
        if node.globals:
            return 'exec %s in %s' % (node.expr.accept(self),
                                      node.globals.accept(self))
        return 'exec %s' % node.expr.accept(self)

    def visit_extslice(self, node):
        """return an astng.ExtSlice node as string"""
        return ','.join( [dim.accept(self) for dim in node.dims] )

    def visit_for(self, node):
        """return an astng.For node as string"""
        fors = 'for %s in %s:\n%s' % (node.target.accept(self),
                                    node.iter.accept(self),
                                    self._stmt_list( node.body))
        if node.orelse:
            fors = '%s\nelse:\n%s' % (fors, self._stmt_list(node.orelse))
        return fors

    def visit_from(self, node):
        """return an astng.From node as string"""
        return 'from %s import %s' % ('.' * (node.level or 0) + node.modname,
                                      _import_string(node.names))

    def visit_function(self, node):
        """return an astng.Function node as string"""
        decorate = node.decorators and node.decorators.accept(self)  or ''
        docs = node.doc and '\n%s"""%s"""' % (INDENT, node.doc) or ''
        return '\n%sdef %s(%s):%s\n%s' % (decorate, node.name, node.args.accept(self),
                                        docs, self._stmt_list(node.body))

    def visit_genexpr(self, node):
        """return an astng.GenExpr node as string"""
        return '(%s %s)' % (node.elt.accept(self), ' '.join([n.accept(self)
                                                    for n in node.generators]))

    def visit_getattr(self, node):
        """return an astng.Getattr node as string"""
        return '%s.%s' % (node.expr.accept(self), node.attrname)

    def visit_global(self, node):
        """return an astng.Global node as string"""
        return 'global %s' % ', '.join(node.names)

    def visit_if(self, node):
        """return an astng.If node as string"""
        ifs = ['if %s:\n%s' % (node.test.accept(self), self._stmt_list(node.body))]
        if node.orelse:# XXX use elif ???
            ifs.append('else:\n%s' % self._stmt_list(node.orelse))
        return '\n'.join(ifs)

    def visit_ifexp(self, node):
        """return an astng.IfExp node as string"""
        return '%s if %s else %s' % (node.body.accept(self),
                node.test.accept(self), node.orelse.accept(self))

    def visit_import(self, node):
        """return an astng.Import node as string"""
        return 'import %s' % _import_string(node.names)

    def visit_keyword(self, node):
        """return an astng.Keyword node as string"""
        return '%s=%s' % (node.arg, node.value.accept(self))

    def visit_lambda(self, node):
        """return an astng.Lambda node as string"""
        return 'lambda %s: %s' % (node.args.accept(self), node.body.accept(self))

    def visit_list(self, node):
        """return an astng.List node as string"""
        return '[%s]' % ', '.join([child.accept(self) for child in node.elts])

    def visit_listcomp(self, node):
        """return an astng.ListComp node as string"""
        return '[%s %s]' % (node.elt.accept(self), ' '.join([n.accept(self)
                                                for n in node.generators]))

    def visit_module(self, node):
        """return an astng.Module node as string"""
        docs = node.doc and '"""%s"""\n\n' % node.doc or ''
        return docs + '\n'.join([n.accept(self) for n in node.body]) + '\n\n'

    def visit_name(self, node):
        """return an astng.Name node as string"""
        return node.name

    def visit_pass(self, node):
        """return an astng.Pass node as string"""
        return 'pass'

    def visit_print(self, node):
        """return an astng.Print node as string"""
        nodes = ', '.join([n.accept(self) for n in node.values])
        if not node.nl:
            nodes = '%s,' % nodes
        if node.dest:
            return 'print >> %s, %s' % (node.dest.accept(self), nodes)
        return 'print %s' % nodes

    def visit_raise(self, node):
        """return an astng.Raise node as string"""
        if node.exc:
            if node.inst:
                if node.tback:
                    return 'raise %s, %s, %s' % (node.exc.accept(self),
                                                node.inst.accept(self),
                                                node.tback.accept(self))
                return 'raise %s, %s' % (node.exc.accept(self),
                                        node.inst.accept(self))
            return 'raise %s' % node.exc.accept(self)
        return 'raise'

    def visit_return(self, node):
        """return an astng.Return node as string"""
        if node.value:
            return 'return %s' % node.value.accept(self)
        else:
            return 'return'

    def visit_index(self, node):
        """return a astng.Index node as string"""
        return node.value.accept(self)

    def visit_set(self, node):
        """return an astng.Set node as string"""
        return '{%s}' % ', '.join([child.accept(self) for child in node.elts])

    def visit_setcomp(self, node):
        """return an astng.SetComp node as string"""
        return '{%s %s}' % (node.elt.accept(self), ' '.join([n.accept(self)
                                                for n in node.generators]))

    def visit_slice(self, node):
        """return a astng.Slice node as string"""
        lower = node.lower and node.lower.accept(self) or ''
        upper = node.upper and node.upper.accept(self) or ''
        step = node.step and node.step.accept(self) or ''
        if step:
            return '%s:%s:%s' % (lower, upper, step)
        return  '%s:%s' % (lower, upper)

    def visit_subscript(self, node):
        """return an astng.Subscript node as string"""
        return '%s[%s]' % (node.value.accept(self), node.slice.accept(self))

    def visit_tryexcept(self, node):
        """return an astng.TryExcept node as string"""
        trys = ['try:\n%s' % self._stmt_list( node.body)]
        for handler in node.handlers:
            trys.append(handler.accept(self))
        if node.orelse:
            trys.append('else:\n%s' % self._stmt_list(node.orelse))
        return '\n'.join(trys)

    def visit_tryfinally(self, node):
        """return an astng.TryFinally node as string"""
        return 'try:\n%s\nfinally:\n%s' % (self._stmt_list( node.body),
                                        self._stmt_list(node.finalbody))

    def visit_tuple(self, node):
        """return an astng.Tuple node as string"""
        return '(%s)' % ', '.join([child.accept(self) for child in node.elts])

    def visit_unaryop(self, node):
        """return an astng.UnaryOp node as string"""
        if node.op == 'not':
            operator = 'not '
        else:
            operator = node.op
        return '%s%s' % (operator, node.operand.accept(self))

    def visit_while(self, node):
        """return an astng.While node as string"""
        whiles = 'while %s:\n%s' % (node.test.accept(self),
                                    self._stmt_list(node.body))
        if node.orelse:
            whiles = '%s\nelse:\n%s' % (whiles, self._stmt_list(node.orelse))
        return whiles

    def visit_with(self, node): # 'with' without 'as' is possible
        """return an astng.With node as string"""
        as_var = node.vars and " as (%s)" % (node.vars.accept(self)) or ""
        withs = 'with (%s)%s:\n%s' % (node.expr.accept(self), as_var,
                                        self._stmt_list( node.body))
        return withs

    def visit_yield(self, node):
        """yield an ast.Yield node as string"""
        yi_val = node.value and (" " + node.value.accept(self)) or ""
        expr = 'yield' + yi_val
        if node.parent.is_statement:
            return expr
        else:
            return "(%s)" % (expr,)


class AsStringVisitor3k(AsStringVisitor):
    """AsStringVisitor3k overwrites some AsStringVisitor methods"""

    def visit_excepthandler(self, node):
        if node.type:
            if node.name:
                excs = 'except %s as %s' % (node.type.accept(self),
                                        node.name.accept(self))
            else:
                excs = 'except %s' % node.type.accept(self)
        else:
            excs = 'except'
        return '%s:\n%s' % (excs, self._stmt_list(node.body))

    def visit_nonlocal(self, node):
        """return an astng.Nonlocal node as string"""
        return 'nonlocal %s' % ', '.join(node.names)

    def visit_raise(self, node):
        """return an astng.Raise node as string"""
        if node.exc:
            if node.cause:
                return 'raise %s from %s' % (node.exc.accept(self),
                                             node.cause.accept(self))
            return 'raise %s' % node.exc.accept(self)
        return 'raise'

    def visit_starred(self, node):
        """return Starred node as string"""
        return "*" + node.value.accept(self)


def _import_string(names):
    """return a list of (name, asname) formatted as a string"""
    _names = []
    for name, asname in names:
        if asname is not None:
            _names.append('%s as %s' % (name, asname))
        else:
            _names.append(name)
    return  ', '.join(_names)


if sys.version_info >= (3, 0):
    AsStringVisitor = AsStringVisitor3k

# this visitor is stateless, thus it can be reused
to_code = AsStringVisitor()