How to debug TypeError: required field "lineno" missing from expr?
Terry Reedy
tjreedy at udel.edu
Mon Jun 29 16:59:23 EDT 2015
On 6/29/2015 7:17 AM, Terry Reedy wrote:
> On 6/29/2015 3:08 AM, Laura Creighton wrote:
>> In a message of Mon, 29 Jun 2015 02:14:43 +0100, Mark Lawrence writes:
>>> Purely as an exercise I've been converting Grant Jenks' pypatt[1] from
>>> 2.7 to 3.4. I've managed to sort out most of the required changes by
>>> checking on what I can see with an AST pretty printer[2]. So it's
>>> rather frustrating to have the compile stage throw the error given in
>>> the subject line.
>>
>> Are you trying to use ast.copy_location recursively somewhere?
>> http://bugs.python.org/issue3530 Maybe you have found something else
>> that doesn't work recursively?
The issue is that copy_location is not recursive and does not fix
children of the node being fixed, whereas the example method, copied
from the NodeTransformer doc, creates 3 new nodes, not just 1, that need
fixing. I reopened the issue as a doc issue to fix the example and
recommend the use of recursive fix_missing_locations() instead of the
non-recursive copy_location.
The only other location-related function in ast is increment_lineno,
which also works on multiple nodes. I would not be surprised is Mark's
issue results from Mark or someone else copying the bad doc example.
> I do not understand the closing of this issue given that a) the failing
> part of the code is copied from the doc (3.4 has the same in the
> docstring) and b) that there is no recursion for a single node ast,
> which the example should be.
The original ast is actually an Expression with a Name. But the issue
is that the Name is replaced with a Subscript with Name and Str children
and all three need locations added.
> The error message comes from
> F:\Python\dev\34\Python\Python-ast.c: 3752:
> PyErr_SetString(PyExc_TypeError, "required field \"lineno\" missing from
> stmt");
--
Terry Jan Reedy
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