Fix `Partition()` w/ `size` greater than the length of the input

[LebedevRI]

complete() only worked correctly if at least a single full partition has been produced already, otherwise the buf would be smaller than the xform(rf).size, and we get buffer overflow, etc.

I've added sufficient test coverage for the issue, that now passes.

I have stumbled into this while trying to write a reduction tree, not sure if this is something that might be interesting here?

Fixes https://github.com/JuliaFolds/Transducers.jl/issues/528

[codecov[bot]]

Codecov Report

Merging #529 (2bf2e55) into master (c8fa4f2) will increase coverage by 0.09%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #529      +/-   ##
==========================================
+ Coverage   95.33%   95.43%   +0.09%     
==========================================
  Files          32       32              
  Lines        2230     2232       +2     
==========================================
+ Hits         2126     2130       +4     
+ Misses        104      102       -2     

Flag	Coverage Δ
Pkg.test	94.55% <100.00%> (+0.09%)	:arrow_up:
Run.test	95.20% <100.00%> (+<0.01%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/library.jl	98.44% <100.00%> (+<0.01%)	:arrow_up:
src/nondeterministic_threading.jl	90.81% <0.00%> (+2.04%)	:arrow_up:

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[MasonProtter]

Hey @LebedevRI I’ve finally got the test suite working. Could you rebase on Master? That should get all tests passing and then I can merge.

[LebedevRI]

I've rebased, but did nothing other than that. I don't know if this still works, or needs further changes.

[MasonProtter]

Great, thanks @LebedevRI!

[LebedevRI]

Thank you!