Use inspect.signature to enable Python 3 only features when defining tasks

[rsxm]

Fix #372

[rsxm]

Locally all tests have passed when running "invoke test":

Ran 596 tests in 2.798 seconds
OK (10 skipped)

[bitprophet]

Linking this to #357.

@jr-minnaar: a) thanks! b) if you can, please check the assertion made in #357 about how there might be even more to this than simple getargspec/getfullargspec - it'd be nice for this to degrade gracefully as much as possible, so if there's things even newer/"better" than getfullargspec, it'd be rad to use them if it makes sense. (So e.g. inspect.signature -> not there? getfullargspec -> also not there? getargspec)

[rsxm]

Thanks, I'll have a look at #357. Do I leave this pull request open while investigating or what is the protocol?

[codecov-io]

Codecov Report

Merging #373 into master will decrease coverage by 0.02%.
The diff coverage is 90.9%.

@@            Coverage Diff             @@
##           master     #373      +/-   ##
==========================================
- Coverage   92.83%   92.81%   -0.03%     
==========================================
  Files          21       21              
  Lines        2149     2156       +7     
  Branches      379      382       +3     
==========================================
+ Hits         1995     2001       +6     
  Misses        113      113              
- Partials       41       42       +1

Impacted Files	Coverage Δ
invoke/tasks.py	95.48% <90.9%> (-0.41%)	❌

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6e21055...a50329a. Read the comment docs.

[bitprophet]

Leaving this open is fine, I assume you'd just push more commits once you finish looking into that stuff. Thanks!

[rsxm]

I've updated the pull request to now use inspect.signature instead of inspect.getargspec.

I've also addressed one of the TODO's that related to the argspec method. Let me know if I should rather take that out of this pull request.

[bitprophet]

If you have a sec can you write out a list of which Python versions have which of getargspec, getfullargspec, signature, etc? I'd like to make sure we're not leaving e.g. Python 3.3 or 2.6 or whatever, out in the cold here.

If "just" both of getargspec and signature covers all of 2.6, 2.7, 3.3, 3.4, 3.5+...that'd be fine :) (We no longer bother with 3.2 so maybe that's where some of the earlier confusion came in.)

[rsxm]

If "just" both of getargspec and signature covers all of 2.6, 2.7, 3.3, 3.4, 3.5+...that'd be fine :) (We no longer bother with 3.2 so maybe that's where some of the earlier confusion came in.)

That indeed seems to be the case:

Python 2	getargspec	getfullargspec	signature
2.6	✅ Changed	❌ No	❌ No
2.7	✅ Yes	❌ No	❌ No

Python 3	getargspec	getfullargspec	signature
3.2	⚠️ Deprecated	✅ Yes	❌ No
3.3	⚠️ Deprecated	✅ Yes	✅ New
3.4	⚠️ Deprecated	✅ Changed	✅ Yes
3.5	⚠️ Deprecated	⚠️ Deprecated	✅ Yes
3.6	⚠️ Deprecated	⚠️ Deprecated	✅ Yes

[bitprophet]

Awesomesauce, thanks! Also excellent use of emoji ❤️

[rsxm]

Hi @bitprophet

I see you've moved this pull request to the 0.16 milestone. I've rebased and rerun tests. Also removed some extra changes not related to this issue.

Looking forward to the next release :-)

[FranklinChen]

I'm sad to see this wasn't fixed for the 1.0.0 release that just came out.

[haydenflinner]

There's actually an easier way than the PR for this commit gives, since decorator includes a similar thing to what this PR implements

commit 14c88f9b3bc7525df66a3d4ec2ad13a733e08bf1
Author: Hayden Flinner <[email protected]>
Date:   Mon Nov 5 20:19:02 2018 -0500

    Fixed getfullargspec on Py2.

diff --git a/invoke/tasks.py b/invoke/tasks.py
index 7fa67025..79833b8f 100644
--- a/invoke/tasks.py
+++ b/invoke/tasks.py
@@ -8,7 +8,7 @@ from copy import deepcopy
 import inspect
 import types
 
-from .util import six
+from .util import six, getfullargspec
 
 if six.PY3:
     from itertools import zip_longest
@@ -156,7 +156,7 @@ class Task(object):
         # TODO: __call__ exhibits the 'self' arg; do we manually nix 1st result
         # in argspec, or is there a way to get the "really callable" spec?
         func = body if isinstance(body, types.FunctionType) else body.__call__
-        spec = inspect.getfullargspec(func)
+        spec = getfullargspec(func)
         arg_names = spec.args[:]
 
         # Collect into for regular args
diff --git a/invoke/util.py b/invoke/util.py
index a574580a..c70251c3 100644
--- a/invoke/util.py
+++ b/invoke/util.py
@@ -22,6 +22,7 @@ try:
     from .vendor.lexicon import Lexicon  # noqa
     from .vendor import six
     from .vendor.six.moves import reduce  # noqa
+    from .vendor.decorator import getfullargspec
 
     if six.PY3:
         from .vendor import yaml3 as yaml  # noqa

You can see it working here, I did it to use type-annotations for an invoke extension I worked on.

[dperetti]

Please 🙏

[bryzgaloff]

@bitprophet does anything stop this PR from being merged? @rsxm are you using some other workaround for that issue?

[jrabbit]

This is a priority for me, I can review or advocate or whatever we need to do to finish this?

[rsxm]

@bryzgaloff hi, I still use my patched branch with this fix. I don't update this dependency much, so haven't looked at this in a long time.

[offbyone]

I can attest to this patch fixing my encounter with #357, at least.

[paambaati]

@bitprophet I noticed that you've been committing again recently. Would you mind reviewing this PR once again and merging?