ARROW-13768: [R] Allow JSON to be an optional component

[karldw]

I templated from ARROW-11735. Let's see how all the tests go!

[github-actions]

https://issues.apache.org/jira/browse/ARROW-13768

[github-actions]

⚠️ Ticket has not been started in JIRA, please click 'Start Progress'.

[nealrichardson]

I think this looks good, thanks for doing this! @ianmcook since you did the dataset/parquet changes, could you glance over this too?

[karldw]

I should add that I'm more confident in my R than my C++ programming. There are almost certainly mistakes here.

The standard checks all have JSON on. Something like test-r-minimal-build might exercise these changes more.

[nealrichardson]

The minimal build checks ran and look good

[ianmcook]

Thanks for doing this @karldw!

You've waded into a tricky part of the package that has some dependencies on external systems :) When we add new cflags to the arrow R package build scripts, we also need to open PRs add them in two other repositories:

autobrew/scripts

You can template this on autobrew/scripts#10

conda-forge/r-arrow-feedstock

You can template this on conda-forge/r-arrow-feedstock#30

[karldw]

Should there be a change to PKG_LIBS here? I couldn't find a -l.*json flag in use in the code. These other changes include adding e.g. -lparquet or -larrow_dataset

[ianmcook]

Should there be a change to PKG_LIBS here?

I believe not; I don’t think there is any -l flag for that

[nealrichardson]

we also need to open PRs add them in two other repositories

Good catch, I had this feeling that I was forgetting some other place this would break. We can merge this PR now though right? Just need to make sure those other scripts are updated before the October release (though we can do it sooner than that).

[karldw]

The minimal build checks ran and look good

I was looking to test the case where the R side is compiled against a C++ library built with ARROW_JSON=OFF. Did that get run? Sorry if I missed it.

[nealrichardson]

Check the "R package without arrow" build

[ianmcook]

we also need to open PRs add them in two other repositories

Good catch, I had this feeling that I was forgetting some other place this would break. We can merge this PR now though right? Just need to make sure those other scripts are updated before the October release (though we can do it sooner than that).

Yes, the only other thing that I think needs to be done is to apply the same change made in autobrew/scripts#11 to the file r/tools/autobrew in this repo. @karldw could you do that please? Thank you!

[nealrichardson]

Should there be a change to PKG_LIBS here?

I believe not; I don’t think there is any -l flag for that

rapidjson is (I believe) vendored on the fly and pulled into libarrow itself; if it were bundled like other third-party dependencies, it would get zipped up into libarrow_bundled_dependencies. So we're good.

[nealrichardson]

@github-actions crossbow submit test-r-minimal-build

[github-actions]

Revision: 2355196

Submitted crossbow builds: ursacomputing/crossbow @ actions-810

Task	Status
test-r-minimal-build

[nealrichardson]

Also it looks like there is an example in read_json_arrow that needs the @examplesIf clause updated: https://dev.azure.com/ursacomputing/crossbow/_build/results?buildId=10941&view=logs&j=0da5d1d9-276d-5173-c4c4-9d4d4ed14fdb&t=d9b15392-e4ce-5e4c-0c8c-b69645229181&l=370

You will need the dev version of roxygen2 to update the docs because the released version doesn't have @examplesIf.

Looks like there's also a merge conflict now but fortunately it's on a generated file (arrowExports.cpp) so you can rebase and resolve that conflict however you want, then next time you build and install, the codegen script will run and fix it. (Happy to help if that all gets too messy too.)

[karldw]

Also it looks like there is an example in read_json_arrow that needs the @examplesIf clause updated: https://dev.azure.com/ursacomputing/crossbow/_build/results?buildId=10941&view=logs&j=0da5d1d9-276d-5173-c4c4-9d4d4ed14fdb&t=d9b15392-e4ce-5e4c-0c8c-b69645229181&l=370

You will need the dev version of roxygen2 to update the docs because the released version doesn't have @examplesIf.

Ah, thanks! I'm surprised by that, since I thought I had already set @examplesIf arrow_with_json(). Maybe because I hadn't exported arrow_with_json? Let's see how things go now that I'm exporting.

[ianmcook]

@github-actions crossbow submit test-r-minimal-build

[github-actions]

Revision: 88ff084

Submitted crossbow builds: ursacomputing/crossbow @ actions-811

Task	Status
test-r-minimal-build

[ianmcook]

Looks great, thanks @karldw! I will merge.