Improve / Clear ASDL generator

[isidentical]

BPO	40528
Nosy	@serhiy-storchaka, @pablogsal, @isidentical
PRs	bpo-40528: Improve & clear a bunch of internal asdl thing #19952 bpo-40528: Improve AST generation script to do builds simultaneously #19968 bpo-40528: Implement a metadata system for ASDL Generator #20193 bpo-40528: move asdl identifier collection to the new metadata system #26858 bpo-40528: fix is_simple(sum)s behavior for attributes #26918

^{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 2021-06-27.14:59:34.107>
created_at = <Date 2020-05-06.11:17:00.247>
labels = ['interpreter-core', '3.9']
title = 'Improve / Clear ASDL generator'
updated_at = <Date 2021-06-27.14:59:34.107>
user = 'https://github.com/isidentical'

bugs.python.org fields:

activity = <Date 2021-06-27.14:59:34.107>
actor = 'BTaskaya'
assignee = 'none'
closed = True
closed_date = <Date 2021-06-27.14:59:34.107>
closer = 'BTaskaya'
components = ['Interpreter Core']
creation = <Date 2020-05-06.11:17:00.247>
creator = 'BTaskaya'
dependencies = []
files = []
hgrepos = []
issue_num = 40528
keywords = ['patch']
message_count = 17.0
messages = ['368235', '368238', '368239', '368240', '368245', '368247', '368248', '368250', '368251', '368252', '368257', '368365', '369281', '396353', '396477', '396583', '396584']
nosy_count = 3.0
nosy_names = ['serhiy.storchaka', 'pablogsal', 'BTaskaya']
pr_nums = ['19952', '19968', '20193', '26858', '26918']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue40528'
versions = ['Python 3.9']

[isidentical]

• Better error messages with punctuation
• Py_UNREACHABLE() for unreachable states
• Removal of several 'unused' and 'undocumented (in Zephyr ASDL spec) built-in types.

[serhiy-storchaka]

You just read my thoughts. That's what I was going to do tonight. ;)

[isidentical]

You just read my thoughts. That's what I was going to do tonight. ;)

:) Awesome. Well I'll plan to continue this; @pablogsal and I was discussing the idea of extracting _ast.AST subclasses to python level (which would save a lot of time for new additions). So my primary goal is clearing bunch of old stuff / making it extendable and clean.

[isidentical]

Currently working on implementing some items from this TODO https://github.com/eliben/asdl_parser/blob/master/TODO

[pablogsal]

I was also thinking about getting rid of "string" nodes and just use Constant for those. Having the strings raw make the AST inconsistent because nodes that are 'strings' do not have line numbers and other metadata, making tools that need the source to report stuff more complex than it should.

What are your opinions on this @serhiy.storchaka and @BTaskaya?

[isidentical]

I was also thinking about getting rid of "string" nodes and just use Constant for those. Having the strings raw make the AST inconsistent because nodes that are 'strings' do not have line numbers and other metadata, making tools that need the source to report stuff more complex than it should.

I'm +1 on that (especially for finding import aliases, as we discussed earlier), if necessary precautions happen to ensure minimum breakage (from what I understand, it is something that will break everyone's code. Maybe we can implement custom Constant.__str__? and other different things to ensure it breaks small).

[serhiy-storchaka]

"string" is only used for

• type_comment in a number of statements
• kind in Constant
• tag in type_ignore

For which of them a line number is meaningful and useful?

[pablogsal]

For which of them a line number is meaningful and useful?

Apologies, I was thinking of 'identifier', which is basically a PyObject representing a string. For instance, when parsing function calls like

x = ast.parse("f(x=435)")

the 'arg' attribute of the keyword is just the string 'x', without any metadata about it (like column offset and such).

[isidentical]

Oh, I confuse with it identifier. IMHO replacing identifier with Constant would infer position in some cases.

[isidentical]

A real world example would be tools like unimport, that try to remove a certain part of import by looking start/end column offsets. Before (lib2to3), it was using tokens to manipulate source, and what I can tell is that having position information on multi line from imports would be a life saver for tool authors.

[pablogsal]

New changeset 091951a by Batuhan Taskaya in branch 'master':
bpo-40528: Improve and clear several aspects of the ASDL definition code for the AST (GH-19952)
091951a