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