Add precompile helper

[IanButterworth]

No description provided.

[timholy]

Let's hold off on this for a second; I took a quick look myself, and it seems there are quite a few inference problems that can be fixed. Once you eat dessert it's actually harder to eat your vegetables because the caching masks triggers of inference.

EDIT: xref #36

[codecov-io]

Codecov Report

Merging #35 (4825d21) into master (31191cb) will decrease coverage by 14.35%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           master      #35       +/-   ##
===========================================
- Coverage   88.79%   74.43%   -14.36%     
===========================================
  Files          12       13        +1     
  Lines         562      669      +107     
===========================================
- Hits          499      498        -1     
- Misses         63      171      +108     

Impacted Files	Coverage Δ
src/TiffImages.jl	100.00% <ø> (ø)
src/precompile.jl	0.00% <0.00%> (ø)
src/ifds.jl	97.61% <0.00%> (-0.02%)	⬇️

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[IanButterworth]

@timholy Small thought.. The timings in the precompile directives file are nice, but frustratingly break git diffs, so it's harder to tell what changes. Any way to have the best of both worlds..? 🤔

[timholy]

One point: you could conceivably just use precomp_gen.jl as the precompiler. Yes, you'd be creating actual objects when the package gets compiled, but that's not the worst thing in the world, and it is shorter. Check out the precompile file in JuliaImages/ImageCore.jl#157. You would have to return something so that the compiler doesn't decide to elide all the precompilation code, but that shouldn't be too hard.

Another one: if you do keep the explicit precompile directives, I almost always put an @assert in front of them now so I know when they go stale.

[IanButterworth]

I'm a bit confused as to why codecov is reporting a reduction here, but should be good to merge @tlnagy

[IanButterworth]

Oh.. right, codecov is being run on both 1.5 and nightly. So on one the precompiles are being skipped

[tlnagy]

This looks good to me. Why are the precompiles only included for 1.6-dev+?

Also will I need to rerun this on every release?

[IanButterworth]

I was being lazy and hadn't checked that they pass for 1.5. Just updated as it works locally for 1.5.3.
If you want to check that they work for older versions, feel free to update or merge (once the CI re-runs)

[IanButterworth]

Also will I need to rerun this on every release?

That is one of the down-sides of precompile directives over just running some code, which @timholy was advocating for above. I didn't go that way because snooping.jl uses the whole test suite to generate precompile directives, so should have better coverage than that just in precomp_gen.jl, minus the include at the end. If you think that's enough, then we could just run that code during precomp instead.

[timholy]

FYI I've not noticed downsides to precompiling for any version after 1.4.2, as long as they are the same precompiles. But before 1.4.2 you can trigger segfaults by precompiling so it's better to be safe.

[tlnagy]

Also will I need to rerun this on every release?

If you think that's enough, then we could just run that code during precomp instead.

I think I would prefer that. I know myself and I'll struggle to remember to rebuild the precompilation signatures regularly.

Could you also add N0f16 and Float32 to the type list? I think that should cover common use cases.

[IanButterworth]

Great, yeah that simplifies this then. I also added GrayA and RGBA.

This PR should be squash merged. I didn't rebase squash in case anyone wants to review the intermediate snoop scripts in the future.

@timholy looks like FileIO is hitting a precompile directive error on nightly on != ubuntu

ERROR: LoadError: AssertionError: precompile(f, (Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, typeof(load), String))
Stacktrace:
 [1] _precompile_()
   @ FileIO ~/.julia/packages/FileIO/C7O10/src/precompile.jl:52

[timholy]

looks like FileIO is hitting a precompile directive error on nightly on != ubuntu

That will be fixed when JuliaIO/FileIO.jl#295 merges. Should I go ahead and do that or wait longer? From my standpoint it's ready.

[IanButterworth]

I just commented. Sorry, not had time to give the diff a proper review, but from my perspective I see no reason to not go ahead if you consider it ready

[tlnagy]

Can I go ahead and merge this? Little confused by the linked issue.

[IanButterworth]

It should be safe to merge, but you might want to re-run CI to check?

[IanButterworth]

If we can merge this, can we get out a new release and merge the FileIO Tiff update?

(On my phone, hence the lack of PR links)