chore(hogql): Full error & NULL handling in C++ parser (1.0.0)

[Twixes]

Changes

This is the final stage of making the C++ parser production-ready: to prevent any and all segfaults, we must check for NULL pointers in all Python/C API call returning PyObject*, and for -1 in all calls returning an integer (e.g. PyList_Size(), but also PyObject_SetAttrString()).

I had to do a bunch more reading of CPython docs and code to get all of this right, which is why this is not the way I initially wrote the converter… even though that would have made for much more readable PRs than this one.

The way I went about making sure nothing is missed is basically just checking every match for this regex:

(Py(Object_|Unicode_|Dict_|List_|Long_|Float_|Tuple_|Import_|_(Va)?Build))|build_ast_node\(|is_ast_node_instance\(|get_ast_enum_member\(

I had to rewrite nearly each of the 200+ call sites to handle every situation where a NULL might pop up. This means throwing an error after decrementing refcounts for all PyObject*s in scope.

Additionally, I made sure we similarly clean up refcounts if any visit() call throws (which can be due to a Python exception, but also a syntax exception).

There's some new info on all of the above in hogql_parser/CONTRIBUTING.md.

How did you test this code?

All parser tests succeed.

[mariusandra]

Looks great, though I'm definitely unable to verify all these changes.