Attribute node in a decorator has wrong end_col_offset

[lysnikolaou]

BPO	39579
Nosy	@gvanrossum, @lysnikolaou, @pablogsal, @miss-islington
PRs	bpo-39579: Change Attribute end_col_offset to point at the current node #18405 [3.8] bpo-39579: Fix Attribute end_col_offset to point at the current node (GH-18405) #18408

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2020-02-08.00:22:17.066>
created_at = <Date 2020-02-07.14:44:54.322>
labels = ['interpreter-core', '3.8', '3.9']
title = 'Attribute node in a decorator has wrong end_col_offset'
updated_at = <Date 2020-07-02.00:19:06.909>
user = 'https://github.com/lysnikolaou'

bugs.python.org fields:

activity = <Date 2020-07-02.00:19:06.909>
actor = 'flherne'
assignee = 'none'
closed = True
closed_date = <Date 2020-02-08.00:22:17.066>
closer = 'gvanrossum'
components = ['Interpreter Core']
creation = <Date 2020-02-07.14:44:54.322>
creator = 'lys.nikolaou'
dependencies = []
files = []
hgrepos = []
issue_num = 39579
keywords = ['patch']
message_count = 5.0
messages = ['361595', '361614', '361617', '372796', '372799']
nosy_count = 5.0
nosy_names = ['gvanrossum', 'lys.nikolaou', 'pablogsal', 'miss-islington', 'flherne']
pr_nums = ['18405', '18408']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue39579'
versions = ['Python 3.8', 'Python 3.9']

[lysnikolaou]

There is a problem with the end_col_offset of nested Attribute nodes in decorators. For example, parsing

@a.b.c
def f(): pass

produces the following AST tree (part):

decorator_list=[
    Attribute(
        value=Attribute(
            value=Name(
                id="a",
                ctx=Load(),
                lineno=1,
                col_offset=1,
                end_lineno=1,
                end_col_offset=2,
            ),
            attr="b",
            ctx=Load(),
            lineno=1,
            col_offset=1,
            end_lineno=1,
            *end_col_offset=6*,
        ),
        attr="c",
        ctx=Load(),
        lineno=1,
        col_offset=1,
        end_lineno=1,
        end_col_offset=6,
    )
],

Note that the Attribute node with attr="b" has end_col_offset=6, while it should actually be 4.

[gvanrossum]

New changeset d2e1098 by Lysandros Nikolaou in branch 'master':
bpo-39579: Fix Attribute end_col_offset to point at the current node (GH-18405)
d2e1098

[miss-islington]

New changeset 8b9cebc by Lysandros Nikolaou in branch '3.8':
[3.8] bpo-39579: Fix Attribute end_col_offset to point at the current node (GH-18405) (GH-18408)
8b9cebc

[flherne]

Note: this change causes a regression in kdev-python because our code was based on (and worked around) the long-standing previous behaviour; it produces broken results given the 'fixed' offset.

I shall have to write a patch with a version-check before our next stable release.

While the new behaviour is more logical, I'm not convinced that deliberate API breakage in a stable release - for something that's not a recent regression - was a good idea.

[flherne]

Sorry, on further inspection it was the other AST range change https://bugs.python.org/issue39474 , not this one.