How to debug TypeError: required field "lineno" missing from expr?

[Mark Lawrence]

On 29/06/2015 21:59, Terry Reedy wrote:
> 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.
>

FTR there is no call to copy_location in Grant's existing code.  Whether 
or not one is actually needed in 3.4 when compared to 2.7 is another 
question.

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence