gh-133390: Support SQL keyword completion for sqlite3 CLI

[tanloong]

This adds tab-completion for the 147 SQLite Keywords. A whitespace is appended to completion candidates for users' convenience and to mimic the behavior of sqlite3 tool.

• Issue: Support completion for sqlite3 command-line interface #133390

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[StanFromIreland]

This needs a whatsnew entry, (maybe a note in the docs?), a NEWS entry and tests.

This is quite limited completion so I guess it could work.

[picnixz]

I think we need a separate nodule for this because if we want to have a smarter completion later the code is better to be isolated, so something like sqlite3._completer.

If possible, can we have an autogenerated list of keywords? and those keywords could also be stored in a (private) module-level list.

[picnixz]

Please add tests

[tanloong]

Yes, tests is coming. I will try to find a way to autogenerate list of keywords.

[StanFromIreland]

You can mark the pr as a draft.

[tanloong]

Added tests and moved keyword list to module level.

Keywords seems not easy to auto-generate, the SQLite document says they can be accessed by sqlite3_keyword_count() and sqlite3_keyword_name() using C, but I am bad at C and didn't figure out how to call these two at Python level. I think these two functions are not exposed to Python?

[StanFromIreland]

With #133447 in mind the keywords list would be quite handy (I think hardcoding is fine, it doesn't change often anyway). Maybe it could be moved elsewhere, what do you think Benedikt?

[tanloong]

Hi @picnixz, as Stan mentioned, beta freeze is around the corner, but I really hope this can be shipped in 3.14, do you think there is a chance to merge it before beta freeze?

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🤖 New build scheduled with the buildbot fleet by @encukou for commit d681425 🤖

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[erlend-aasland]

For the record:
We could just assert that the result is SQLITE_OK. This is just an out-of-bounds check, and we know that we are within bounds here. OTOH, we don't know how the SQLite internals may change, so let's keep it like it is.

[erlend-aasland]

FTR, CI fails bco. #134077. Let's await a revert or a fix for that.

Otherwise, this looks great. Thank you so much for improving the sqlite3 module, @tanloong. Highly appreciated!

[erlend-aasland]

FTR, I've tested this with new SQLite variants, as well as SQLite 3.23.0 and 3.24.0. Everything works as expected for all versions. I should really get to setting up a build-bot with a SQLite library matrix.

[erlend-aasland]

I only get the "Display all 147 possibilities? (y or n)" prompt with editline, and never on readline. Probably a bug in readline? Or are we missing a configuration option in order to get this to work?

[tanloong]

Readline has a completion-query-items (default value 100) option to determine whether or when this prompt should be shown. https://www.gnu.org/software/bash/manual/html_node/Readline-Init-File-Syntax.html#index-completion_002dquery_002ditems

With a default readline config the prompt should have be shown, I suspect there is a config that sets the option to 0 on the testing machine?

[erlend-aasland]

With a default readline config the prompt should have be shown, I suspect there is a config that sets the option to 0 on the testing machine?

Nope. I was a little bit vague in my previous comment: I see the text "Display all 147 possibilities? (y or n)", but it is not shown as a prompt after the first tab. It is only displayed together with the resulting completion list, after the second tab.

IOW: For editline, I get the prompt on the first tab; for readline, I get no prompt, but I see the prompt text after the second tab.

FTR, I already experimented with the completion-query-items option, and it has no impact.

[tanloong]

Try set show-all-if-unmodified on in readline and see if it make the prompt shown on just the first tab? https://www.gnu.org/software/bash/manual/html_node/Readline-Init-File-Syntax.html#index-show_002dall_002dif_002dunmodified

[tanloong]

Thank you very much for the careful review and thorough test! There are so many corners and difficulties that I would have never considered let alone solved, thanks for everyone's help!