symbian-qemu-0.9.1-12/python-2.6.1/Lib/lib2to3/fixes/fix_except.py
author MattD <mattd@symbian.org>
Wed, 10 Mar 2010 16:08:53 +0000
changeset 48 34cd6bf038ac
parent 1 2fb8b9db1c86
permissions -rw-r--r--
Very rough additions to get baseport building after the header reorganisation. Original hardcoded systeminclude paths still left in.

"""Fixer for except statements with named exceptions.

The following cases will be converted:

- "except E, T:" where T is a name:

    except E as T:

- "except E, T:" where T is not a name, tuple or list:

        except E as t:
            T = t

    This is done because the target of an "except" clause must be a
    name.

- "except E, T:" where T is a tuple or list literal:

        except E as t:
            T = t.args
"""
# Author: Collin Winter

# Local imports
from .. import pytree
from ..pgen2 import token
from .. import fixer_base
from ..fixer_util import Assign, Attr, Name, is_tuple, is_list

def find_excepts(nodes):
    for i, n in enumerate(nodes):
        if isinstance(n, pytree.Node):
            if n.children[0].value == 'except':
                yield (n, nodes[i+2])

class FixExcept(fixer_base.BaseFix):

    PATTERN = """
    try_stmt< 'try' ':' suite
                  cleanup=(except_clause ':' suite)+
                  tail=(['except' ':' suite]
                        ['else' ':' suite]
                        ['finally' ':' suite]) >
    """

    def transform(self, node, results):
        syms = self.syms

        tail = [n.clone() for n in results["tail"]]

        try_cleanup = [ch.clone() for ch in results["cleanup"]]
        for except_clause, e_suite in find_excepts(try_cleanup):
            if len(except_clause.children) == 4:
                (E, comma, N) = except_clause.children[1:4]
                comma.replace(Name("as", prefix=" "))

                if N.type != token.NAME:
                    # Generate a new N for the except clause
                    new_N = Name(self.new_name(), prefix=" ")
                    target = N.clone()
                    target.set_prefix("")
                    N.replace(new_N)
                    new_N = new_N.clone()

                    # Insert "old_N = new_N" as the first statement in
                    #  the except body. This loop skips leading whitespace
                    #  and indents
                    #TODO(cwinter) suite-cleanup
                    suite_stmts = e_suite.children
                    for i, stmt in enumerate(suite_stmts):
                        if isinstance(stmt, pytree.Node):
                            break

                    # The assignment is different if old_N is a tuple or list
                    # In that case, the assignment is old_N = new_N.args
                    if is_tuple(N) or is_list(N):
                        assign = Assign(target, Attr(new_N, Name('args')))
                    else:
                        assign = Assign(target, new_N)

                    #TODO(cwinter) stopgap until children becomes a smart list
                    for child in reversed(suite_stmts[:i]):
                        e_suite.insert_child(0, child)
                    e_suite.insert_child(i, assign)
                elif N.get_prefix() == "":
                    # No space after a comma is legal; no space after "as",
                    # not so much.
                    N.set_prefix(" ")

        #TODO(cwinter) fix this when children becomes a smart list
        children = [c.clone() for c in node.children[:3]] + try_cleanup + tail
        return pytree.Node(node.type, children)