coverage#CreateReport: move assertions up

[blueyed]

This makes it easier in case of errors to see where it is coming from.

[dbarnett]

Can you give more context, like what the error looks like w/ and w/o? We use this convention widely across all our plugins, and it'd be unfortunate if the errors aren't precise, but also I'm hesitant to start unwinding this kind of thing everywhere it appears and I don't see any special reason we'd do it here and not everywhere else.

[blueyed]

Currently I am seeing:

Error rendering coverage: ERROR(WrongType): Expected a list. Got a null.

(using google/vim-maktaba#213 to fix the type name)

The error will be the same, but it's easier to figure out where it's coming, since you can easily comment the lines. Not very helpful altogether, but I guess that's where this PR comes from.

When throwing a custom exception you see that it is coming via function coverage#Show[5]..<SNR>110_CoverageShow[9]..coverage#ShowCoverage[45]..15[21]..coverage#CreateReport.

Therefore additionally/instead v:throwpoint should get added to caught exceptions to aid debugging in case of errors.
With v:throwpoint and this PR you will have the correct error line (since previously it's a single line).

[blueyed]

The error/issue I was seeing: #30

[dbarnett]

Sounds like you're saying the issue is that there are 3 ensures in the same statement. We should probably change it around to give a more useful error if it's important that the errors are useful. I guess you can proceed w/ splitting these out if it helps.

[blueyed]

Yup, thanks!

[dbarnett]

(I approved. You have a button to merge the changes now, right?)

[blueyed]

@dbarnett

You have a button to merge the changes now, right?

No.
Did I miss an invite?

[dbarnett]

I approved them so I thought you could. Anyway, I merged them for you.