Current File : //lib64/python3.6/lib2to3/fixes/fix_metaclass.py
"""Fixer for __metaclass__ = X -> (metaclass=X) methods.
The various forms of classef (inherits nothing, inherits once, inherints
many) don't parse the same in the CST so we look at ALL classes for
a __metaclass__ and if we find one normalize the inherits to all be
an arglist.
For one-liner classes ('class X: pass') there is no indent/dedent so
we normalize those into having a suite.
Moving the __metaclass__ into the classdef can also cause the class
body to be empty so there is some special casing for that as well.
This fixer also tries very hard to keep original indenting and spacing
in all those corner cases.
"""
# Author: Jack Diederich
# Local imports
from .. import fixer_base
from ..pygram import token
from ..fixer_util import syms, Node, Leaf
def has_metaclass(parent):
""" we have to check the cls_node without changing it.
There are two possibilities:
1) clsdef => suite => simple_stmt => expr_stmt => Leaf('__meta')
2) clsdef => simple_stmt => expr_stmt => Leaf('__meta')
"""
for node in parent.children:
if node.type == syms.suite:
return has_metaclass(node)
elif node.type == syms.simple_stmt and node.children:
expr_node = node.children[0]
if expr_node.type == syms.expr_stmt and expr_node.children:
left_side = expr_node.children[0]
if isinstance(left_side, Leaf) and \
left_side.value == '__metaclass__':
return True
return False
def fixup_parse_tree(cls_node):
""" one-line classes don't get a suite in the parse tree so we add
one to normalize the tree
"""
for node in cls_node.children:
if node.type == syms.suite:
# already in the preferred format, do nothing
return
# !%@#! oneliners have no suite node, we have to fake one up
for i, node in enumerate(cls_node.children):
if node.type == token.COLON:
break
else:
raise ValueError("No class suite and no ':'!")
# move everything into a suite node
suite = Node(syms.suite, [])
while cls_node.children[i+1:]:
move_node = cls_node.children[i+1]
suite.append_child(move_node.clone())
move_node.remove()
cls_node.append_child(suite)
node = suite
def fixup_simple_stmt(parent, i, stmt_node):
""" if there is a semi-colon all the parts count as part of the same
simple_stmt. We just want the __metaclass__ part so we move
everything after the semi-colon into its own simple_stmt node
"""
for semi_ind, node in enumerate(stmt_node.children):
if node.type == token.SEMI: # *sigh*
break
else:
return
node.remove() # kill the semicolon
new_expr = Node(syms.expr_stmt, [])
new_stmt = Node(syms.simple_stmt, [new_expr])
while stmt_node.children[semi_ind:]:
move_node = stmt_node.children[semi_ind]
new_expr.append_child(move_node.clone())
move_node.remove()
parent.insert_child(i, new_stmt)
new_leaf1 = new_stmt.children[0].children[0]
old_leaf1 = stmt_node.children[0].children[0]
new_leaf1.prefix = old_leaf1.prefix
def remove_trailing_newline(node):
if node.children and node.children[-1].type == token.NEWLINE:
node.children[-1].remove()
def find_metas(cls_node):
# find the suite node (Mmm, sweet nodes)
for node in cls_node.children:
if node.type == syms.suite:
break
else:
raise ValueError("No class suite!")
# look for simple_stmt[ expr_stmt[ Leaf('__metaclass__') ] ]
for i, simple_node in list(enumerate(node.children)):
if simple_node.type == syms.simple_stmt and simple_node.children:
expr_node = simple_node.children[0]
if expr_node.type == syms.expr_stmt and expr_node.children:
# Check if the expr_node is a simple assignment.
left_node = expr_node.children[0]
if isinstance(left_node, Leaf) and \
left_node.value == '__metaclass__':
# We found an assignment to __metaclass__.
fixup_simple_stmt(node, i, simple_node)
remove_trailing_newline(simple_node)
yield (node, i, simple_node)
def fixup_indent(suite):
""" If an INDENT is followed by a thing with a prefix then nuke the prefix
Otherwise we get in trouble when removing __metaclass__ at suite start
"""
kids = suite.children[::-1]
# find the first indent
while kids:
node = kids.pop()
if node.type == token.INDENT:
break
# find the first Leaf
while kids:
node = kids.pop()
if isinstance(node, Leaf) and node.type != token.DEDENT:
if node.prefix:
node.prefix = ''
return
else:
kids.extend(node.children[::-1])
class FixMetaclass(fixer_base.BaseFix):
BM_compatible = True
PATTERN = """
classdef<any*>
"""
def transform(self, node, results):
if not has_metaclass(node):
return
fixup_parse_tree(node)
# find metaclasses, keep the last one
last_metaclass = None
for suite, i, stmt in find_metas(node):
last_metaclass = stmt
stmt.remove()
text_type = node.children[0].type # always Leaf(nnn, 'class')
# figure out what kind of classdef we have
if len(node.children) == 7:
# Node(classdef, ['class', 'name', '(', arglist, ')', ':', suite])
# 0 1 2 3 4 5 6
if node.children[3].type == syms.arglist:
arglist = node.children[3]
# Node(classdef, ['class', 'name', '(', 'Parent', ')', ':', suite])
else:
parent = node.children[3].clone()
arglist = Node(syms.arglist, [parent])
node.set_child(3, arglist)
elif len(node.children) == 6:
# Node(classdef, ['class', 'name', '(', ')', ':', suite])
# 0 1 2 3 4 5
arglist = Node(syms.arglist, [])
node.insert_child(3, arglist)
elif len(node.children) == 4:
# Node(classdef, ['class', 'name', ':', suite])
# 0 1 2 3
arglist = Node(syms.arglist, [])
node.insert_child(2, Leaf(token.RPAR, ')'))
node.insert_child(2, arglist)
node.insert_child(2, Leaf(token.LPAR, '('))
else:
raise ValueError("Unexpected class definition")
# now stick the metaclass in the arglist
meta_txt = last_metaclass.children[0].children[0]
meta_txt.value = 'metaclass'
orig_meta_prefix = meta_txt.prefix
if arglist.children:
arglist.append_child(Leaf(token.COMMA, ','))
meta_txt.prefix = ' '
else:
meta_txt.prefix = ''
# compact the expression "metaclass = Meta" -> "metaclass=Meta"
expr_stmt = last_metaclass.children[0]
assert expr_stmt.type == syms.expr_stmt
expr_stmt.children[1].prefix = ''
expr_stmt.children[2].prefix = ''
arglist.append_child(last_metaclass)
fixup_indent(suite)
# check for empty suite
if not suite.children:
# one-liner that was just __metaclass_
suite.remove()
pass_leaf = Leaf(text_type, 'pass')
pass_leaf.prefix = orig_meta_prefix
node.append_child(pass_leaf)
node.append_child(Leaf(token.NEWLINE, '\n'))
elif len(suite.children) > 1 and \
(suite.children[-2].type == token.INDENT and
suite.children[-1].type == token.DEDENT):
# there was only one line in the class body and it was __metaclass__
pass_leaf = Leaf(text_type, 'pass')
suite.insert_child(-1, pass_leaf)
suite.insert_child(-1, Leaf(token.NEWLINE, '\n'))
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