gh-133390: Support basic completion for sqlite3 command-line interface

[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?

[bedevere-app]

Thanks for making the requested changes!

@picnixz: please review the changes made to this pull request.

[picnixz]

The SQLITE_KEYWORDS is moved from C back to Python.

If you want it in C, you need to combine int sqlite3_keyword_count(void) and int sqlite3_keyword_name(int,const char**,int*);. Stated otherwise, you need to first count the number of keywords, then loop over this number and get the n-th keyword using sqlite3_keyword_name. But for now, let's simply keep them in Python. We'll do it in a follow-up PR (or I'll do it as the task is a bit harder)

[picnixz]

You can yourself to ACKS if it's not already done.

Changes were made.

[picnixz]

On my side it looks great but I'll also want @erlend-aasland to have a look as he's the main maintainer. Maybe he'l ask for some stylistic changes (in which case I'm sorry if I suggested something wrong).

[StanFromIreland]

This is no longer freely customizable by users via sys.ps1 ?

[tanloong]

On my side it looks great but I'll also want @erlend-aasland to have a look as he's the main maintainer. Maybe he'l ask for some stylistic changes (in which case I'm sorry if I suggested something wrong).

Thank you so much for your review. Really appreciate your guidance!

[tanloong]

The test_completion_order() fails. The SQLITE_KEYWORDS given by sqlite3_keyword_name() and sqlite3_keyword_count() is not in alphabetical order, but GNU Readline always sorts completions before displaying them.

Unfortunately I didn't find a disable-completion-sorting-like option in GNU Readline's document. There is an rl_sort_completion_matches in Readline's source code but it's not exposed as a config flag.

Can we remove this test_completion_order(), as the order of displayed candidates is controlled by GNU Readline.

[picnixz]

Let's just check that the completion of nothing returns all keywords. You can sort the SQLITE_KEYWORDS list before checking for the equality (I think it's better not to sort it at the C level as it could be helpful in the future for someone interacting with python and C)