diff options
Diffstat (limited to 'lib/python2.7/lib2to3/fixes/fix_metaclass.py')
| -rw-r--r-- | lib/python2.7/lib2to3/fixes/fix_metaclass.py | 228 |
1 files changed, 228 insertions, 0 deletions
diff --git a/lib/python2.7/lib2to3/fixes/fix_metaclass.py b/lib/python2.7/lib2to3/fixes/fix_metaclass.py new file mode 100644 index 0000000..45f9937 --- /dev/null +++ b/lib/python2.7/lib2to3/fixes/fix_metaclass.py @@ -0,0 +1,228 @@ +"""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 Name, 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 == u'__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 = u'' + 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, u')')) + node.insert_child(2, arglist) + node.insert_child(2, Leaf(token.LPAR, u'(')) + 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, u',')) + meta_txt.prefix = u' ' + else: + meta_txt.prefix = u'' + + # 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 = u'' + expr_stmt.children[2].prefix = u'' + + 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, u'pass') + pass_leaf.prefix = orig_meta_prefix + node.append_child(pass_leaf) + node.append_child(Leaf(token.NEWLINE, u'\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, u'pass') + suite.insert_child(-1, pass_leaf) + suite.insert_child(-1, Leaf(token.NEWLINE, u'\n')) |