python-3.6.zip added from Github

README.cosmo contains the necessary links.

third_party/python/Lib/lib2to3/fixes/fix_metaclass.py

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+"""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'))