[pytest-dev] Enabling viewing of rewritten AST trees as Python

[Tom Viner]

One extra note:

`py.test -s` is required to see rewritten AST output, even for failing
tests, because the output comes while
tests are being collected and rewritten, not during the execution of a
test. So pytest's "show output upon
fail" cannot help here.

If anyone knows how to tie the output to particular tests, that would be
great.


On 1 March 2015 at 23:01, Tom Viner <tom at viner.tv> wrote:

> Thanks for your ideas Floris, I've managed to get it working with
> your pytest_configure suggestion.
>
> The only extra bit was having to disable reading the cached pyc files that
> pytest writes, as these skip my monkeypatch.
>
> Take a look, it's simple to use:
> https://gist.github.com/tomviner/c3537c2f2b2b8172f83e
>
> If there's any demand, I could easily make this a pip installable pytest
> plugin.
>
> On 13 November 2014 at 23:34, Floris Bruynooghe <flub at devork.be> wrote:
>
>> Hi Tom,
>>
>> On 9 November 2014 19:18, Tom Viner <tom at viner.tv> wrote:
>> > The four options I can think of to gain access to this variable:
>> > - monkey patch rewrite.rewrite_asserts
>> > - edit rewrite_asserts and paste in the logging code above:
>> >     -- temporarily, by each developer, on each occasion required
>> >     -- permanently, but only running when a certain debug flag is active
>> > - expose the rewritten AST via a new hook
>> >
>> > monkey patch is my preferred option, because if I can make it work, a
>> plugin
>> > could be written. I just need some help to find an appropriate hook to
>> do
>> > the monkey patching before pytest gets going with the
>> AssertionRewritingHook
>> > and calls rewrite_asserts. Without knowledge of an early-running hook, I
>> > could only get this working by patching rewrite_asserts then calling
>> > pytest.main myself, see
>> > https://gist.github.com/tomviner/13c95cdb1e159028fc0b
>>
>> Would this work by using monkeypatching, but using a method on
>> _pytest.pytester.TmpTestDir which wraps around inline_run or
>> inline_runsource?  That would seem like a fairly reasonable approach.
>> It could simply skip with an appropriate message if the meta lib is
>> importable and print the reversed python code to stdout for capsys to
>> collect.
>>
>> If you would like to go the full plugin way I believe you just need to
>> hook in before collection happens.  I imagine pytest_configure would
>> be a reasonable hook for that, but have to admit I haven't tried it.
>>
>>
>> Regards,
>> Floris
>>
>
>
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