`packages` file or `packages` text

[schloerke]

For build-wasm-packages's packages input parameter, I am wondering what the underlying motivation for using a new/unfamiliar file format.

I'm not against it, just want to understand it.

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• packages ('packages') - A file path to a text file containing a list of R package references.

---

Currently, r-lib/actions's setup-r-dependencies has three locations to where it will look for packages to install.

• needs - Config/Needs fields to install from the DESCRIPTION, the Config/Needs/ prefix will be automatically included.
• packages: - default deps::., any::sessioninfo. Which package(s) to install. The default installs the dependencies of the package in the working directory and the sessioninfo package. Separate multiple packages by newlines or commas.
• extra-packages - One or more extra package references to install. Separate each reference by newlines or commas for more than one package.

1. It will look for Config/Needs/<NEEDS> via the needs parameter.

2. packages is a default that hardly anyone sets manually because in the context of checking an R package, this field should not be changed. (You will typically always want to install deps::., any::sessioninfo

3. extra-packages is used by authors who do not want to clutter their DESCRIPTION file or for one-off changes.

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If possible, I'd like to leverage r-lib/actions existing approach.

If r-wasm/actions is to be used within R packages, then I'd like to utilize the DESCRIPTION's Config/Needs/wasm field as the typical entrypoint, with a backup of packages or extra-packages.

If r-wasm/actions is to be used within a localized wasm-friendly CRAN repo, then packages file is a great choice for providing information.

If using a packages file, should it ever contain more fields such as description or R version or any other meta data? If so, should we upgrade the file to a yaml (to support comments) or DCF file (similar to the DESCRIPTION file)?

[schloerke]

After typing all this out, I am understanding it as it should be an easy way for devs to declare what packages are being used. While using packages as a string in the GHA workflow, those values are hidden away from the repo. Therefore, we should keep packages as a filename whose file contents contain the packages being used.

It still leaves the questions

• Will there ever be any more information?"
• If so, should we upgrade it to a yaml file? (This would allow for comments and or key/value pairs in the future, such as R version or any other meta info)

[georgestagg]

For build-wasm-packages's packages input parameter, I am wondering what the underlying motivation for using a new/unfamiliar file format.

The current one-line-per-entry text format for the packages file is simply legacy from when we first started experimenting with building R packages for Wasm. Originally the process was powered by shell scripts, where using that kind of file as input makes a lot of sense.

I am not opposed to changing the format. In fact, I really like the idea to match setup-r-dependencies, where the relevant data is in the GHA workflow file and DESCRIPTION. Consistency is good and enables knowledge transfer for current users of r-lib/actions. So, my vote would be to indeed move towards that model.

The only issue I see is that I'd still like to be able to use this workflow in a kind of meta-repo, one without an R package or DESCRIPTION file in it. Under that use case, I still see the benefit of a flat text file. I think a yaml file would be fine. Another format I considered was renv lock files. However, I believe it should be possible to specify packages easily when writing such files by hand, and so I steered away from the lock file format.

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Will there ever be any more information?

I am unsure, perhaps the intended webR version or R version would be useful? In the future we could use tagged r-wasm/webr Docker containers to build packages for a specific version of webR.

Note that, currently, package list entries are passed to rwasm::add_list(). This supports pkgdepnds style package references, which are already fairly expressive so extra information such as specific package source and versioning can be encoded. I think things like deps::. should also work.

Either way, switching to yaml would future-proof these files in a nice way for if/when we do want to track [web]R versions or other information. I would be OK with that.

---

Right, so what do you think about the following plan?

First, we switch around build-wasm-packages so as to match setup-r-dependencies behaviour:

• Add the needs parameter and automatically search for Config/Needs/[needs] in the DESCRIPTION file for packages.

• Change packages to take in text. Default to something like deps::. or file::. so that "this" package is installed by default. Ensure such references work with rwasm::add_pkg() as expected.

• Add an extra-packages text field.

The above three package lists should be combined into an character R vector and passed to rwasm::add_pkg(), rather than using add_list() like currently.

In addition, we handle the case where there is no DESCRIPTION file in the repo and it's more like a meta-package:

• Tweak rwasm::add_list() to work by taking in a yaml file and parsing it for a list of packages. Otherwise, it works as before. Perhaps we also rename it to rwasm::add_yaml() or something similar.

• Ensure that the action still works when there is no DESCRIPTION file to be read for Config/Needs/wasm.

• If packages is a single line and ends in .yml, change behaviour so as to pass the given filename to rwasm::add_list(). This will match current behaviour, and the special case should be documented clearly.