split assert - avoid split if message, handle comments

[jakkdl]

Not triggering on messages was easy, but handling comments was ... hilariously stupid. Turns out the relevant comments can be put in like ... six or seven places? So the code is absolutely stupid and unreadable, but it at least works for all test cases currently written.

TODO:

• clean up code, can surely deduplicate code handling the left and right side (even though they, of course, differ slightly)
• add comments (good luck understanding anything atm)
• write/generate weird tests (some weird combo of lines/comments/statements might put comments in some even more obscure location).

[jakkdl]

@Zac-HD I think I'm hitting a bug somewhere that's making it impossible to differentiate

assert(
  a # first
  and b # second
)

with

assert(a # first  # second
  and b
)

(which is a pretty common issue, since having multiple #'s on the same line is common with noqa etc. Though one could ship the feature knowing that some comments will be in weird places sometimes)

When running the tests, they both show up with identical SimpleLineStatements in my visitor - but when I parse those strings in my interpreter into either cst.parse_statement or cst.parse_module they are different, as they should be. So something somewhere collapses the two comments in the first one to both be added to updated_node.trailing_whitespace.comment, but they "should" be in updated_node.body[0].operator.whitespace_before.first_line.comment and updated_node[0].rpar[0].whitespace_before.first_line.comment.

I'll try digging into the testing infrastructure to see if the file is read in some janky way or what's going on, but thought I'd raise it since you might have a better idea of what's going on.

[jakkdl]

Oh derp, it's because shed runs black on it first which reformats it into

assert a and b  # first  # second

[Zac-HD]

Ah, right. I'm disinclined to care more about comments than Black itself does, so if you can't reproduce the pattern by using longer variable names I would just skip this case.

[jakkdl]

once I figured out that Black's been messing with my test cases everything makes a lot more sense, so will have a finished implementation soon. Can't 100% guarantee that comments are in the right places, but I don't wanna throw away any comments at least.

[jakkdl]

Done!
Only improvements would be running the refactor before black (which doesn't seem worth it unless other refactors also starts wanting to run before black), and could make it handle

assert a and b; assert c and d

but black will split those up anyway and then they're handled.

[jakkdl]

The PR did end up madly complicated, and I'm somewhat tempted to want to throw it in the bin - the former implementation straight up eating comments is probably the only thing that makes it worth it. Though if I'd redone it from scratch I'd write a wayy simpler implementation and not give a crap on where the comments go.

[Zac-HD]

Whew, yeah, that certainly is an implementation. Agree that "not eating comments" is important and also that it's not so ugly as to be worth refactoring at this stage. Thanks for the feature; splitting assertions should make it easier to understand what's going on in logs when things fail!