Convert documentation examples into testsuite tests

[lgritz]

The documentation contains lots of code examples embedded in the text. Some of them have bugs or are incorrect in various ways, either because they were never correct (having been typed in for the docs themselves and never directly tested), or were once correct but now the APIs have changed and the example was never updated to match.

To combat this, we would like to go through all the documentation, and to the greatest extent possible, convert every significant code example in the docs into a test -- that is, into actual code that will compile and run every time we run the testsuite -- and then the documentation will merely include the test code by reference, so they can never get out of sync again.

Explanation: https://github.com/OpenImageIO/oiio/wiki/Converting-documentation-examples-to-tests

There are dozens and dozens of code examples in the docs that we could do this with. Small steps -- do this for one or two at a time, that's fine.

[lgritz]

I'm not going to formally assign the issue to anyone, because no one's piece of it is going to close the issue (until there are literally no more examples left to convert in the docs). This will take probably dozens of PRs (and people, maybe) before it's truly complete.

Please feel free to work on it. Maybe leave a comment here saying which particular example(s) you want to do, so that others who also want to contribute to the task won't pick the same specific bit that you did.

[lgritz]

I would recommend that anybody wanting to leave a note here declaring that they want to work on an example pick ONE specific code example to start with, and drive that to a complete accepted PR, before declaring a whole section or chapter off-limits to others. Get the hang of the process with something small, figure out how rapidly you can do the conversions, and then for round 2, you can reserve a larger section that might be a few days of work for you.

[buddly27]

Hi @lgritz, I'm interested in picking up the conversion for the examples within imagebufalgo.rst as part of Dev Days. As a OIIO newbie, it seems like an excellent opportunity to get to know the API better!

[lgritz]

That's great. It's a big chapter with a lot of example, maybe you want to claim a particular section of that chapter to start with?

[buddly27]

I can start with common principles and move to pattern generation if it goes smoothly. Unless someone else wants to get it :)

[lgritz]

You claimed it first, it's yours!

I think that for examples where in the docs we show images, what we'll want to do is also have the docs switch to actually using the reference images from the examples. If that seems like too much to do all at once, you don't have to do it all in one step. We can move the code first, then change the location of the images.

[MichaelRCarroll-Intel]

Hi @buddly27 and @lgritz... I'm on for dev days as well and new to the source. I'll take ImageBuf: Image Buffers to start. It has 3 (and a half) examples. After that, I could grab a section of imagebufalgo or perhaps another doc area that has an example1() template stub...

@lgritz On the half example... The last "example" has an elipsis section by design ("same as above") ... It is used to illustrate an option for code abstraction... Should I assume this should best be positioned in the repository with the full example?

@lgritz On reference images, do you mean the hrefs in the documentation rst markdown that point to generated images that live in this folder or this folder

Thanks

[lgritz]

Sounds great. Start with that chapter, see how it goes. (Sometimes fooling around with the docs and the testsuite can take longer than expected.)

The ellipsis is just to make the code example not be too long by mostly repeating what is directly above it. I suppose that in that final example, it didn't need to show make_black_impl at all. Looking at the examples I did in the other chapter, you should be able to see how to use the :start-after: and :end-before: to clip particular regions to appear in the docs. So the testsuite code can be a full working example, with only the key section actually appearing in the docs.

Yeah, by reference images, I mean in the ref/ directory of each test are the sample output that is the standard for the test (i.e., "if we run the test and it matches the reference output, the test passes; if it differs, the test fails"). If the docs are clarified by showing the image, than we may also reference the image in the docs themselves, but not all code examples are clarified by also showing specific image output.

[CheeksTheGeek]

Hi @lgritz @MichaelRCarroll-Intel @buddly27 and everyone else planning to take/already working on a slice of this mega task or just wanting to browse the examples! I prepared a GitHub Project to track who's taking which example on OIIO docs examples to tests syncing for #3992 | Github Project and the overall progress. Since people will have different times and different sizes for this contribution, I made one for each example I could find. Will try to keep it updated with what you guys are doing.

If possible, when someone is picking up a task or made progress on one or there's an example not in this list and you want to add it, ping me to add it to this project, and I'll update it asap.

[CheeksTheGeek]

For Dev Days, I'll start working on ImageOutput! Since the first two, Simple Write and Writing Scanline were covered in the Prototype PR, I'll continue from Write Individual Tiles

[buddly27]

Good morning everyone! I started a draft PR with one converted example to ensure we are all on the same page. I will update it and rebase my commit with the remaining examples from the "imagebufalgo" section throughout the day. Please let me know if you spot any issues!

@lgritz Would you prefer the PR to target an intermediate branch to ease collaborative work, or is it fine to target master?