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94 lines
3.3 KiB
94 lines
3.3 KiB
6 years ago
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"""Fixer for except statements with named exceptions.
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The following cases will be converted:
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- "except E, T:" where T is a name:
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except E as T:
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- "except E, T:" where T is not a name, tuple or list:
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except E as t:
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T = t
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This is done because the target of an "except" clause must be a
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name.
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- "except E, T:" where T is a tuple or list literal:
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except E as t:
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T = t.args
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"""
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# Author: Collin Winter
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# Local imports
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from .. import pytree
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from ..pgen2 import token
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from .. import fixer_base
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from ..fixer_util import Assign, Attr, Name, is_tuple, is_list, syms
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def find_excepts(nodes):
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for i, n in enumerate(nodes):
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if n.type == syms.except_clause:
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if n.children[0].value == 'except':
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yield (n, nodes[i+2])
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class FixExcept(fixer_base.BaseFix):
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BM_compatible = True
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PATTERN = """
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try_stmt< 'try' ':' (simple_stmt | suite)
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cleanup=(except_clause ':' (simple_stmt | suite))+
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tail=(['except' ':' (simple_stmt | suite)]
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['else' ':' (simple_stmt | suite)]
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['finally' ':' (simple_stmt | suite)]) >
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"""
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def transform(self, node, results):
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syms = self.syms
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tail = [n.clone() for n in results["tail"]]
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try_cleanup = [ch.clone() for ch in results["cleanup"]]
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for except_clause, e_suite in find_excepts(try_cleanup):
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if len(except_clause.children) == 4:
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(E, comma, N) = except_clause.children[1:4]
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comma.replace(Name("as", prefix=" "))
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if N.type != token.NAME:
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# Generate a new N for the except clause
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new_N = Name(self.new_name(), prefix=" ")
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target = N.clone()
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target.prefix = ""
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N.replace(new_N)
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new_N = new_N.clone()
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# Insert "old_N = new_N" as the first statement in
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# the except body. This loop skips leading whitespace
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# and indents
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#TODO(cwinter) suite-cleanup
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suite_stmts = e_suite.children
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for i, stmt in enumerate(suite_stmts):
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if isinstance(stmt, pytree.Node):
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break
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# The assignment is different if old_N is a tuple or list
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# In that case, the assignment is old_N = new_N.args
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if is_tuple(N) or is_list(N):
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assign = Assign(target, Attr(new_N, Name('args')))
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else:
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assign = Assign(target, new_N)
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#TODO(cwinter) stopgap until children becomes a smart list
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for child in reversed(suite_stmts[:i]):
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e_suite.insert_child(0, child)
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e_suite.insert_child(i, assign)
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elif N.prefix == "":
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# No space after a comma is legal; no space after "as",
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# not so much.
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N.prefix = " "
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#TODO(cwinter) fix this when children becomes a smart list
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children = [c.clone() for c in node.children[:3]] + try_cleanup + tail
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return pytree.Node(node.type, children)
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