| 1 | """Fixer for except statements with named exceptions.
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| 2 |
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| 3 | The following cases will be converted:
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| 4 |
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| 5 | - "except E, T:" where T is a name:
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| 6 |
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| 7 | except E as T:
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| 8 |
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| 9 | - "except E, T:" where T is not a name, tuple or list:
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| 10 |
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| 11 | except E as t:
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| 12 | T = t
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| 13 |
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| 14 | This is done because the target of an "except" clause must be a
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| 15 | name.
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| 16 |
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| 17 | - "except E, T:" where T is a tuple or list literal:
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| 18 |
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| 19 | except E as t:
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| 20 | T = t.args
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| 21 | """
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| 22 | # Author: Collin Winter
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| 23 |
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| 24 | # Local imports
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| 25 | from .. import pytree
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| 26 | from ..pgen2 import token
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| 27 | from .. import fixer_base
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| 28 | from ..fixer_util import Assign, Attr, Name, is_tuple, is_list, syms
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| 29 |
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| 30 | def find_excepts(nodes):
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| 31 | for i, n in enumerate(nodes):
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| 32 | if n.type == syms.except_clause:
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| 33 | if n.children[0].value == u'except':
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| 34 | yield (n, nodes[i+2])
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| 35 |
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| 36 | class FixExcept(fixer_base.BaseFix):
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| 37 | BM_compatible = True
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| 38 |
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| 39 | PATTERN = """
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| 40 | try_stmt< 'try' ':' (simple_stmt | suite)
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| 41 | cleanup=(except_clause ':' (simple_stmt | suite))+
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| 42 | tail=(['except' ':' (simple_stmt | suite)]
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| 43 | ['else' ':' (simple_stmt | suite)]
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| 44 | ['finally' ':' (simple_stmt | suite)]) >
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| 45 | """
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| 46 |
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| 47 | def transform(self, node, results):
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| 48 | syms = self.syms
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| 49 |
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| 50 | tail = [n.clone() for n in results["tail"]]
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| 51 |
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| 52 | try_cleanup = [ch.clone() for ch in results["cleanup"]]
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| 53 | for except_clause, e_suite in find_excepts(try_cleanup):
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| 54 | if len(except_clause.children) == 4:
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| 55 | (E, comma, N) = except_clause.children[1:4]
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| 56 | comma.replace(Name(u"as", prefix=u" "))
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| 57 |
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| 58 | if N.type != token.NAME:
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| 59 | # Generate a new N for the except clause
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| 60 | new_N = Name(self.new_name(), prefix=u" ")
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| 61 | target = N.clone()
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| 62 | target.prefix = u""
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| 63 | N.replace(new_N)
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| 64 | new_N = new_N.clone()
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| 65 |
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| 66 | # Insert "old_N = new_N" as the first statement in
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| 67 | # the except body. This loop skips leading whitespace
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| 68 | # and indents
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| 69 | #TODO(cwinter) suite-cleanup
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| 70 | suite_stmts = e_suite.children
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| 71 | for i, stmt in enumerate(suite_stmts):
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| 72 | if isinstance(stmt, pytree.Node):
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| 73 | break
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| 74 |
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| 75 | # The assignment is different if old_N is a tuple or list
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| 76 | # In that case, the assignment is old_N = new_N.args
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| 77 | if is_tuple(N) or is_list(N):
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| 78 | assign = Assign(target, Attr(new_N, Name(u'args')))
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| 79 | else:
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| 80 | assign = Assign(target, new_N)
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| 81 |
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| 82 | #TODO(cwinter) stopgap until children becomes a smart list
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| 83 | for child in reversed(suite_stmts[:i]):
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| 84 | e_suite.insert_child(0, child)
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| 85 | e_suite.insert_child(i, assign)
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| 86 | elif N.prefix == u"":
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| 87 | # No space after a comma is legal; no space after "as",
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| 88 | # not so much.
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| 89 | N.prefix = u" "
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| 90 |
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| 91 | #TODO(cwinter) fix this when children becomes a smart list
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| 92 | children = [c.clone() for c in node.children[:3]] + try_cleanup + tail
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| 93 | return pytree.Node(node.type, children)
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