3.14 field annotation not covered

[nickdrozd]

The following snippet gets counted as 100% coverage under 3.13 and earlier versions, but under 3.14 it is counted as having a missing line:

class X:
    x: int  # <-- not covered under 3.14

python3.14 -m coverage run asdf.py && python3.14 -m coverage combine --quiet && python3.14 -m coverage report --fail-under 100
Name      Stmts   Miss Branch BrPart  Cover
-------------------------------------------
asdf.py       2      1      0      0    50%
-------------------------------------------
TOTAL         2      1      0      0    50%
Coverage failure: total of 50 is less than fail-under=100

Adding from __future__ import annotations causes everything to be counted:

from __future__ import annotations

class X:
    x: int  # <-- covered

Could have something to do with https://docs.python.org/3.14/whatsnew/3.14.html#whatsnew314-pep649?

[nedbat]

This definitely is because of deferred annotations. I'm not sure what to do here. The fact is there is code that has not been run. But also, it is likely never to be run, and it's fine that it isn't run.

But it can have errors. This will be an error if you run it in 3.13:

class X:
    x: inttttt
    y = 1

% python3.13 att.py
Traceback (most recent call last):
  File "/Users/ned/coverage/trunk/att.py", line 1, in <module>
    class X:
        x: inttttt
        y = 1
  File "/Users/ned/coverage/trunk/att.py", line 2, in X
    x: inttttt
       ^^^^^^^
NameError: name 'inttttt' is not defined

In 3.14, it won't error, but it will if you try to get the annotation:

class X:
    x: inttttt
    y = 1

from annotationlib import get_annotations, Format
get_annotations(X, format=Format.VALUE)

% python3.14 att.py
Traceback (most recent call last):
  File "/Users/ned/coverage/trunk/att.py", line 7, in <module>
    get_annotations(X, format=Format.VALUE)
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/pyenv/pyenv/versions/3.14.0a3/lib/python3.14/annotationlib.py", line 707, in get_annotations
    ann = _get_dunder_annotations(obj)
  File "/usr/local/pyenv/pyenv/versions/3.14.0a3/lib/python3.14/annotationlib.py", line 842, in _get_dunder_annotations
    ann = _BASE_GET_ANNOTATIONS(obj)
  File "/Users/ned/coverage/trunk/att.py", line 2, in __annotate__
    x: inttttt
       ^^^^^^^
NameError: name 'inttttt' is not defined

[nedbat]

btw, I also opened a discussion thread about this: https://discuss.python.org/t/how-should-coverage-py-treat-deferred-annotations/74990

[nickdrozd]

As a user, my feeling is that if the field annotation is considered covered in 3.13 with from __future__ import annotations, then it should also be considered covered under 3.14 without the import.

Here is a naive suggestion. I assume there is a line somewhere to the effect of:

if has_future_annotations_import():
    field_annotation.count_as_covered()

Maybe that could be changed to:

if has_future_annotations_import() or PY_VER_314_PLUS:
    field_annotation.count_as_covered()

[nedbat]

All of the annotations are put into code objects called __annotate__, so I can ignore those when looking for executable lines, and the problem is fixed in commit 2d04835.

[nickdrozd]

Tested; works. Thanks!

[nedbat]

This is now released as part of coverage 7.6.10.