bpo-40956: Use Argument Clinic in sqlite3 module

[erlend-aasland]

https://bugs.python.org/issue40956

[erlend-aasland]

There's a couple more ref leaks in this PR that I haven't been able to fix yet, @berkerpeksag. (I should have checked this before pushing, sorry 'bout that.) At least one of the ref leaks are related to isolation_level (connection.c). I'll let you know when I've pinned those down.

[erlend-aasland]

I've updated the PR and fixed the following:

• Only apply Argument Clinic (don't change parameter names, variable names, any other code)
• Apply AC to all methods and function (even prepare_protocol.c)
• Fixed all ref. leaks (Checked with ./python.exe -m test -F -r -j1 -R 3:10 test_sqlite)

Note 1: I've used _PyObject_CallMethodId* iso. pysqlite_cache_get() (fc89d4c853c498b8e51edd6787bdb8bcacd7279c) and pysqlite_connection_commit() (f646fdebfc810b30fc122922f0230e1b8b0d78c0), and iso. the cursor.execute* calls in connection.c (f646fdebfc810b30fc122922f0230e1b8b0d78c0). AFAICS, that should be an acceptable and clean solution.

Note 2: Converting _sqlite3.connect and _sqlite3.Connection.__init__ is not trivial. The "best" solution I could come up with (without recreating args and kwargs) was to use PyObject_CallFunctionObjArgs. However, then I need to ensure that none of the arguments are NULL, so I had to copy parts of the isolation_level code from connection.c. Very ugly. I'm sure there's a better way to do this, but I don't know the C API good enough to come up with a better solution right now. (One solution is of course to revert commit 0b456f1c08d879833be6c9d5b161bbc688defe60 ...)

PS. Sorry for force-pushing again. I'll try to avoid it.

[erlend-aasland]

FYI: Rebased against master to resolve conflicts. Tests still pass without reference leaks.

[erlend-aasland]

Here, @vstinner. I'll rebase onto master and force push.

[vstinner]

Sorry, I cannot review a PR which changes 19 files. Also, the PR has many conflicts.

[erlend-aasland]

Sorry, I cannot review a PR which changes 19 files. Also, the PR has many conflicts.

Understandable! Let's repeat the previous exercise; I'll close this PR and split it up in manageable parts.