Deprecate default converters in sqlite3

@ethanfurman

BPO	45858
Nosy	@ethanfurman, @erlend-aasland, @iafisher, @Strongbeard

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assignee = None
closed_at = None
created_at = <Date 2021-11-21.16:46:00.409>
labels = ['type-bug', 'library']
title = 'Deprecate default converters in sqlite3'
updated_at = <Date 2021-11-22.06:16:52.009>
user = 'https://github.com/iafisher'

bugs.python.org fields:

activity = <Date 2021-11-22.06:16:52.009>
actor = 'Strongbeard'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-11-21.16:46:00.409>
creator = 'iafisher'
dependencies = []
files = []
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issue_num = 45858
keywords = []
message_count = 2.0
messages = ['406727', '406728']
nosy_count = 4.0
nosy_names = ['ethan.furman', 'erlendaasland', 'iafisher', 'Strongbeard']
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priority = 'normal'
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status = 'open'
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type = 'behavior'
url = 'https://bugs.python.org/issue45858'
versions = []

Per discussion at https://discuss.python.org/t/fixing-sqlite-timestamp-converter-to-handle-utc-offsets/, the default converters in SQLite3 have several bugs and are probably not worth continuing to maintain, so I propose deprecating them and removing them in a later version of Python.

Since the converters are opt-in, this should not affect most users of SQLite3.

See also bpo-26651 for a related proposal to deprecate the converter/adapter infrastructure entirely.

The proposal in this bug is more limited: remove the default converters (though I think the default adapters should stay), but continue to allow users to define their own converters.

For the record, I created a topic on Discourse, to raise more awareness before starting the deprecation process.

I propose to implement this in two (or possibly three) PRs:

gh-90016: Reword sqlite3 adapter/converter docs #93095
Improve the docs by rewriting the section that deals with custom adapters and converters (reword existing example, add recipes for date/datetime converters). This PR should be backported to 3.11 and 3.10.
[3.11] gh-90016: Reword sqlite3 adapter/converter docs (GH-93095) #94272
[3.10] gh-90016: Reword sqlite3 adapter/converter docs (GH-93095) #94273
gh-90016: Deprecate default sqlite3 adapters and converters #94276
Consider providing a set of date/datetime functions (that work as expected), but don't enable them by default (Serhiy's suggestion)¹

I'm currently -1 on this ↩

pythongh-90016: Reword sqlite3 adapter/converter docs

gh-90016: Reword sqlite3 adapter/converter docs (#93095)

[3.11] pythongh-90016: Reword sqlite3 adapter/converter docs (pythonG…

[3.10] pythongh-90016: Reword sqlite3 adapter/converter docs (pythonG…

Revert 30935 defer bpo45162 to 312 (#94285)

GH-94276 adds deprecation warnings to the default converters/adapters themselves; that is, you'll get a deprecation warning when they're used. However, Ian suggested on the PR to also emit a deprecation warning at connect(), if detect_types is non-zero.

If we are to do this, we should (must) detect if the default adapters and/or converters have been overridden or not.

I believe it may be worth the added complexity to provide a deprecation warning as early as possible. I'll provide a competing PR for this, so it is easier to visualise the added complexity.

OTOH, consider this scenario:

App Developer creates an app that adapts and converts all their custom Python objects. None of them are dates or timestamps, so there is no need for App Developer to override (or even care for) the default adapters. However, as of Python 3.12, they now get deprecation warnings at connect time even if they are not using the default adapters.

gh-90016: Deprecate default sqlite3 adapters and converters (#94276)

Resolved by:

Stopped using default adapters/converters on SQLite backend.

Fix DeprecationWarning on 3.12 with a datetime adapter for sqlite3 (#…

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Deprecate default converters in sqlite3 #90016

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Deprecate default converters in sqlite3 #90016

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iafisher commented on Nov 21, 2021

iafisher commented on Nov 21, 2021

erlend-aasland commented on May 16, 2022

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erlend-aasland commented on Jun 26, 2022

erlend-aasland commented on Jul 20, 2022

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