Add position metadata to alias AST type

@gvanrossum

BPO	43798
Nosy	@gvanrossum, @blueyed, @The-Compiler, @lysnikolaou, @pablogsal, @isidentical, @hauntsaninja, @msuozzo
PRs	bpo-43798: Add source location attributes to alias. #25324

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

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GitHub fields:

assignee = None
closed_at = <Date 2021-04-10.20:57:20.714>
created_at = <Date 2021-04-09.20:28:56.470>
labels = ['interpreter-core', 'type-feature', '3.10']
title = 'Add position metadata to alias AST type'
updated_at = <Date 2021-04-14.15:03:48.078>
user = 'https://github.com/msuozzo'

bugs.python.org fields:

activity = <Date 2021-04-14.15:03:48.078>
actor = 'The Compiler'
assignee = 'none'
closed = True
closed_date = <Date 2021-04-10.20:57:20.714>
closer = 'lys.nikolaou'
components = ['Interpreter Core']
creation = <Date 2021-04-09.20:28:56.470>
creator = 'matthew.suozzo'
dependencies = []
files = []
hgrepos = []
issue_num = 43798
keywords = ['patch']
message_count = 9.0
messages = ['390663', '390673', '390675', '390677', '390740', '390800', '390807', '390901', '390902']
nosy_count = 8.0
nosy_names = ['gvanrossum', 'blueyed', 'The Compiler', 'lys.nikolaou', 'pablogsal', 'BTaskaya', 'hauntsaninja', 'matthew.suozzo']
pr_nums = ['25324']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43798'
versions = ['Python 3.10']

Given the increasing use of long from typing import foo, bar, ... import sequences, it's becoming more desirable to address individual components of the import node. Unfortunately, the ast.alias node doesn't contain source location metadata (e.g. lineno, col_offset).

This metadata would be comparatively easy to add, backwards compatible, and would enable more precise diagnostics e.g. lints.

Ah and one other question: Is this normally the sort of thing that would get backported? It should be very straightforward to do so, at least for 3.9 given the support for the new parser.

I'm okay with this, unless someone has any input on why the alias node should not have line/column info (and did not have it in the first place).

Ah and one other question: Is this normally the sort of thing that would get backported? It should be very straightforward to do so, at least for 3.9 given the support for the new parser.

Unfortunately no, is technically a new feature.

New changeset 75a06f0 by Matthew Suozzo in branch 'master':
bpo-43798: Add source location attributes to alias (GH-25324)
75a06f0

FYI, probably unavoidable, but this appears to have broken pytest pytest-dev/pytest#8539

FYI, probably unavoidable, but this appears to have broken pytest pytest-dev/pytest#8539

What's the problem? alias objects *have* lineno argument:

>>> print(ast.dump(ast.parse("from x import y"), include_attributes=True, indent=4))
Module(
    body=[
        ImportFrom(
            module='x',
            names=[
                alias(
                    name='y',
                    lineno=1,
                    col_offset=14,
                    end_lineno=1,
                    end_col_offset=15)],
            level=0,
            lineno=1,
            col_offset=0,
            end_lineno=1,
            end_col_offset=15)],
    type_ignores=[])

@pablo

@pablo: the problem (referenced in the pytest issue) is that ast.alias has new required arguments now (see also the adjusted test in
75a06f0#diff-3f516b60719dd445d33225e4f316b36e85c9c51a843a0147349d11a005c55937R1060-R1061). That's expected/wanted though (assuming that it should not have "defaults" for B/C), and there's a patch for the issue at pytest-dev/pytest#8540.

Ah, it was not clear from the issue that pytest was constructing nodes by hand. It makes sense now. Thanks!

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Add position metadata to alias AST type #87964

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Add position metadata to alias AST type #87964

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msuozzo commented on Apr 9, 2021

msuozzo commented on Apr 9, 2021

lysnikolaou commented on Apr 9, 2021

pablogsal commented on Apr 9, 2021

lysnikolaou commented on Apr 10, 2021

hauntsaninja commented on Apr 11, 2021

pablogsal commented on Apr 11, 2021

blueyed commented on Apr 12, 2021

pablogsal commented on Apr 12, 2021

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