| 4710c53d |
1 | """Fixer for except statements with named exceptions.\r |
| 2 | \r |
| 3 | The following cases will be converted:\r |
| 4 | \r |
| 5 | - "except E, T:" where T is a name:\r |
| 6 | \r |
| 7 | except E as T:\r |
| 8 | \r |
| 9 | - "except E, T:" where T is not a name, tuple or list:\r |
| 10 | \r |
| 11 | except E as t:\r |
| 12 | T = t\r |
| 13 | \r |
| 14 | This is done because the target of an "except" clause must be a\r |
| 15 | name.\r |
| 16 | \r |
| 17 | - "except E, T:" where T is a tuple or list literal:\r |
| 18 | \r |
| 19 | except E as t:\r |
| 20 | T = t.args\r |
| 21 | """\r |
| 22 | # Author: Collin Winter\r |
| 23 | \r |
| 24 | # Local imports\r |
| 25 | from .. import pytree\r |
| 26 | from ..pgen2 import token\r |
| 27 | from .. import fixer_base\r |
| 28 | from ..fixer_util import Assign, Attr, Name, is_tuple, is_list, syms\r |
| 29 | \r |
| 30 | def find_excepts(nodes):\r |
| 31 | for i, n in enumerate(nodes):\r |
| 32 | if n.type == syms.except_clause:\r |
| 33 | if n.children[0].value == u'except':\r |
| 34 | yield (n, nodes[i+2])\r |
| 35 | \r |
| 36 | class FixExcept(fixer_base.BaseFix):\r |
| 37 | BM_compatible = True\r |
| 38 | \r |
| 39 | PATTERN = """\r |
| 40 | try_stmt< 'try' ':' (simple_stmt | suite)\r |
| 41 | cleanup=(except_clause ':' (simple_stmt | suite))+\r |
| 42 | tail=(['except' ':' (simple_stmt | suite)]\r |
| 43 | ['else' ':' (simple_stmt | suite)]\r |
| 44 | ['finally' ':' (simple_stmt | suite)]) >\r |
| 45 | """\r |
| 46 | \r |
| 47 | def transform(self, node, results):\r |
| 48 | syms = self.syms\r |
| 49 | \r |
| 50 | tail = [n.clone() for n in results["tail"]]\r |
| 51 | \r |
| 52 | try_cleanup = [ch.clone() for ch in results["cleanup"]]\r |
| 53 | for except_clause, e_suite in find_excepts(try_cleanup):\r |
| 54 | if len(except_clause.children) == 4:\r |
| 55 | (E, comma, N) = except_clause.children[1:4]\r |
| 56 | comma.replace(Name(u"as", prefix=u" "))\r |
| 57 | \r |
| 58 | if N.type != token.NAME:\r |
| 59 | # Generate a new N for the except clause\r |
| 60 | new_N = Name(self.new_name(), prefix=u" ")\r |
| 61 | target = N.clone()\r |
| 62 | target.prefix = u""\r |
| 63 | N.replace(new_N)\r |
| 64 | new_N = new_N.clone()\r |
| 65 | \r |
| 66 | # Insert "old_N = new_N" as the first statement in\r |
| 67 | # the except body. This loop skips leading whitespace\r |
| 68 | # and indents\r |
| 69 | #TODO(cwinter) suite-cleanup\r |
| 70 | suite_stmts = e_suite.children\r |
| 71 | for i, stmt in enumerate(suite_stmts):\r |
| 72 | if isinstance(stmt, pytree.Node):\r |
| 73 | break\r |
| 74 | \r |
| 75 | # The assignment is different if old_N is a tuple or list\r |
| 76 | # In that case, the assignment is old_N = new_N.args\r |
| 77 | if is_tuple(N) or is_list(N):\r |
| 78 | assign = Assign(target, Attr(new_N, Name(u'args')))\r |
| 79 | else:\r |
| 80 | assign = Assign(target, new_N)\r |
| 81 | \r |
| 82 | #TODO(cwinter) stopgap until children becomes a smart list\r |
| 83 | for child in reversed(suite_stmts[:i]):\r |
| 84 | e_suite.insert_child(0, child)\r |
| 85 | e_suite.insert_child(i, assign)\r |
| 86 | elif N.prefix == u"":\r |
| 87 | # No space after a comma is legal; no space after "as",\r |
| 88 | # not so much.\r |
| 89 | N.prefix = u" "\r |
| 90 | \r |
| 91 | #TODO(cwinter) fix this when children becomes a smart list\r |
| 92 | children = [c.clone() for c in node.children[:3]] + try_cleanup + tail\r |
| 93 | return pytree.Node(node.type, children)\r |
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