`setup-renv` isn't caching R packages when `RENV_CONFIG_PAK_ENABLED: true`

[gadenbuie]

Describe the bug

I'm using the setup-renv action with RENV_CONFIG_PAK_ENABLED set to true. Unless I'm missing something, the package library isn't included in the cache and packages are always installed fresh with each run.

- name: 📦 Install dependencies with renv
  uses: r-lib/actions/setup-renv@v2
  env:
    RENV_CONFIG_PAK_ENABLED: true
  with:
    cache-version: 2

To Reproduce

Here are two subsequent runs of the same workflow, both spend ~10 minutes installing packages despite the cache hit.

1. https://github.com/posit-conf-2024/level-up-shiny/actions/runs/10239407197/job/28324954289 (13m 49s)
2. https://github.com/posit-conf-2024/level-up-shiny/actions/runs/10239778904/job/28325757466 (14m 46s)

Expected behavior

I was expecting the package library to be included in the cache.

Additional context

Here are a few relevant log lines:

echo "RENV_PATHS_ROOT=/home/runner/work/_temp/renv" >> $GITHUB_ENV
  shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}
  env:
    GITHUB_TOKEN: ***
    GH_TOKEN: ***
    GITHUB_PAT: ***
    BUNDLE_EXT: linux-amd64.deb
    R_LIBS_USER: /home/runner/work/_temp/Library
    TZ: UTC
    _R_CHECK_SYSTEM_CLOCK_: FALSE
    NOT_CRAN: true
    RENV_CONFIG_PAK_ENABLED: true
# ... snip ...
Cache Size: ~15 MB (15681114 B)
/usr/bin/tar -xf /home/runner/work/_temp/3beeaa8e-c7bd-4e38-a6f4-337568925cab/cache.tzst -P -C /home/runner/work/level-up-shiny/level-up-shiny --use-compress-program unzstd
Cache restored successfully
Cache restored from key: Ubuntu 22.04.4 LTS-R version 4.4.1 (2024-06-14)-2-fdd42af88e931ce1a46f09[91](https://github.com/posit-conf-2024/level-up-shiny/actions/runs/10239778904/job/28325757466#step:5:96)e3efb3f513b4abae58b410ca640958cac33f917e
# ... snip ....
- One or more packages recorded in the lockfile are not installed.
- Use `renv::status()` for more details.
i Loaded project root .Rprofile.
The following package(s) will be installed:
- pak [0.7.2]
These packages will be installed into "~/work/level-up-shiny/level-up-shiny/renv/library/linux-ubuntu-jammy/R-4.4/x86_64-pc-linux-gnu".

# Installing packages --------------------------------------------------------
- Installing pak ...                            OK [linked from cache]
Successfully installed 1 package in 8.3 milliseconds.

✔ Updated metadata database: 2.95 MB in 9 files.

ℹ Updating metadata database
✔ Updating metadata database ... done

 
→ Will install 124 packages.
→ Will download [118](https://github.com/posit-conf-2024/level-up-shiny/actions/runs/10239778904/job/28325757466#step:5:124) CRAN packages (83.69 MB).
→ Will download 6 packages with unknown size.

[gaborcsardi]

Where is the package library in this case?

[gadenbuie]

I'm guessing it's in

~/work/level-up-shiny/level-up-shiny/renv/library/linux-ubuntu-jammy/R-4.4/x86_64-pc-linux-gnu

from the log messages, although I don't know exactly. I can say I'm using a standard renv::init() and the only change I made to r-lib/actions/setup-renv@v2 was to add the RENV_CONFIG_PAK_ENABLED: true.

[gadenbuie]

Yeah, caching renv/library is enough, e.g.

- name: Restore package cache
  uses: actions/cache@v4
  with:
    key: ${{ runner.os }}-1-${{ hashFiles('renv.lock') }}
    restore-keys: ${{ runner.os }}-1-
    path: renv/library

(I realized afterwards that runner.os isn't the best choice, maybe runner.name would be better. Actually, runner.os is probably fine for my use case and is definitely better than runner.name.)

• First run (14m 41s)
• Next run (3m 1s, no packages installed)

[github-actions]

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