Import lib2to3.

1 files changed, 82 insertions, 0 deletions

diff --git a/Lib/lib2to3/fixes/fix_raise.py b/Lib/lib2to3/fixes/fix_raise.py
new file mode 100644
index 0000000..2e9ffbc
--- /dev/null
+++ b/Lib/lib2to3/fixes/fix_raise.py
@@ -0,0 +1,82 @@
+"""Fixer for 'raise E, V, T'
+
+raise         -> raise
+raise E       -> raise E
+raise E, V    -> raise E(V)
+raise E, V, T -> raise E(V).with_traceback(T)
+
+raise (((E, E'), E''), E'''), V -> raise E(V)
+raise "foo", V, T               -> warns about string exceptions
+
+
+CAVEATS:
+1) "raise E, V" will be incorrectly translated if V is an exception
+   instance. The correct Python 3 idiom is
+   
+        raise E from V
+        
+   but since we can't detect instance-hood by syntax alone and since
+   any client code would have to be changed as well, we don't automate
+   this.
+"""
+# Author: Collin Winter
+
+# Local imports
+from .. import pytree
+from ..pgen2 import token
+from .import basefix
+from .util import Name, Call, Attr, ArgList, is_tuple
+
+class FixRaise(basefix.BaseFix):
+
+    PATTERN = """
+    raise_stmt< 'raise' exc=any [',' val=any [',' tb=any]] >
+    """
+
+    def transform(self, node, results):
+        syms = self.syms
+
+        exc = results["exc"].clone()
+        if exc.type is token.STRING:
+            self.cannot_convert(node, "Python 3 does not support string exceptions")
+            return
+
+        # Python 2 supports
+        #  raise ((((E1, E2), E3), E4), E5), V
+        # as a synonym for
+        #  raise E1, V
+        # Since Python 3 will not support this, we recurse down any tuple
+        # literals, always taking the first element.
+        if is_tuple(exc):
+          while is_tuple(exc):
+              # exc.children[1:-1] is the unparenthesized tuple
+              # exc.children[1].children[0] is the first element of the tuple
+              exc = exc.children[1].children[0].clone()
+          exc.set_prefix(" ")
+
+        if "val" not in results:
+            # One-argument raise
+            new = pytree.Node(syms.raise_stmt, [Name("raise"), exc])
+            new.set_prefix(node.get_prefix())
+            return new
+
+        val = results["val"].clone()
+        if is_tuple(val):
+            args = [c.clone() for c in val.children[1:-1]]
+        else:
+            val.set_prefix("")
+            args = [val]
+
+        if "tb" in results:
+            tb = results["tb"].clone()
+            tb.set_prefix("")
+
+            e = Call(exc, args)
+            with_tb = Attr(e, Name('with_traceback')) + [ArgList([tb])]
+            new = pytree.Node(syms.simple_stmt, [Name("raise")] + with_tb)
+            new.set_prefix(node.get_prefix())
+            return new
+        else:
+            return pytree.Node(syms.raise_stmt,
+                               [Name("raise"), Call(exc, args)],
+                               prefix=node.get_prefix())