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