Create a renv environment from a crated function

[lorenzwalthert]

The R package https://github.com/r-lib/carrier can be used to create standalone functions. However, it does not manage package dependencies. For this reason, deployment of R functions in arbitrary environments (e.g. deployment of crate functions in mlflow) is not that straight-forward because the user has to manage dependencies manually. I think it would be a great addition to connect renv and carrier, creating a renv.lockfile from a crated function:

fn <- carrier::crate(function(x) styler::style_text(x))
renv::init(bare = TRUE)
renv::snapshot(fn) # make snapshot an S3 generic to handle project (directories) / single files and crated functions

(The API change is just a suggestion, maybe there are better ways to implement this)

Then, to execute the function anywhere, one could just

renv::restore()
renv::activate()
fn <- readRDS('path/to/crated/function.Rds')
fn(...)

I assume most of the functionality to do this already exists in renv, but I could not find them in the exposed API.

This is similar to two existing renv issues that aim at using renv for low(er) level dependency management than an average user:

• files option to renv::snaphsot() to indicate which files to scan for dependencies.  #443
• create lockfile from subset of package requirements #507

I also filed an issue in r-lib/carrier at some point: r-lib/carrier#5

[kevinushey]

I've made some changes on master that should make this kind of workflow possible -- let me know if this captures what you need.

> deps <- renv::dependencies(function() { styler::style_text() })
> pkgs <- unique(deps$Package)
> renv::snapshot(packages = pkgs)
The following package(s) will be updated in the lockfile:

# CRAN ===============================
- R.cache       [* -> 0.14.0]
- R.methodsS3   [* -> 1.8.1]
- R.oo          [* -> 1.24.0]
- R.utils       [* -> 2.10.1]
- assertthat    [* -> 0.2.1]
- backports     [* -> 1.1.10]
- cli           [* -> 2.1.0]
- crayon        [* -> 1.3.4]
- digest        [* -> 0.6.25]
- ellipsis      [* -> 0.3.1]
- fansi         [* -> 0.4.1]
- glue          [* -> 1.4.2]
- lifecycle     [* -> 0.2.0]
- magrittr      [* -> 1.5]
- pillar        [* -> 1.4.6]
- pkgconfig     [* -> 2.0.3]
- purrr         [* -> 0.3.4]
- rematch2      [* -> 2.1.2]
- rprojroot     [* -> 1.3-2]
- styler        [* -> 1.3.2]
- tibble        [* -> 3.0.4]
- utf8          [* -> 1.1.4]
- vctrs         [* -> 0.3.4]
- withr         [* -> 2.3.0]
- xfun          [* -> 0.18]

Do you want to proceed? [y/N]: y
* Lockfile written to '~/scratch/test/renv.lock'.

[lorenzwalthert]

Thanks @kevinushey. It looks like now, with any object that inherits from function (so crate), we can do the following:

fun <- carrier::crate(~styler::style_text(.x))
deps <- renv::dependencies(fun)
renv::snapshot(packages = unique(deps$Package))

Hence, I can achieve what I was after.