Deprecate default converters in sqlite3

[iafisher]

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

^{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 = 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 = []
hgrepos = []
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'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45858'
versions = []

[iafisher]

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.

[iafisher]

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.

[erlend-aasland]

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

Footnotes

1. I'm currently -1 on this ↩