---
title: "Using renv with Continuous Integration"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Using renv with Continuous Integration}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

When building, deploying, or testing with continuous integration (CI) systems
(e.g. [GitHub Actions][github-actions], [Travis CI][travis-ci],
[AppVeyor][appveyor], and others), one often needs to download and install a set
of R packages before the service can be run. Normally, one will have to download
and reinstall these packages on each build, which can often be slow --
especially in environments where binary packages are not available from your R
package repositories.

`renv` can often be helpful in these situations. The general idea is:

1. Call `renv::snapshot()` on your local machine, to generate `renv.lock`;

2. Call `renv::restore()` on your CI service, to restore the project library
   from `renv.lock`;

3. Ensure that the project library, as well as the global `renv` cache, are
   cached by the CI service.

Normally, `renv` will use the R package repositories as encoded in `renv.lock`
during restore, and this will override any repositories set in other locations
(e.g. in `.Rprofile` or `.Rprofile.site`). We'll discuss some strategies for
providing an alternate R package repository to use during restore below.


## GitHub Actions

When using GitHub Actions, you typically need two steps:

1. Cache any packages installed by `renv`,
2. Use `renv::restore()` to restore packages.

As an example, these steps might look like:

```
env:
  RENV_PATHS_ROOT: ~/.local/share/renv

steps:

- name: Cache packages
  uses: actions/cache@v1
  with:
    path: ${{ env.RENV_PATHS_ROOT }}
    key: ${{ runner.os }}-renv-${{ hashFiles('**/renv.lock') }}
    restore-keys: |
      ${{ runner.os }}-renv-

- name: Restore packages
  shell: Rscript {0}
  run: |
    if (!requireNamespace("renv", quietly = TRUE)) install.packages("renv")
    renv::restore()
```

See also the [example][github-actions-renv] on GitHub actions.


## Travis CI

On Travis CI, one can add the following entries to `.travis.yml` to accomplish
the above:

```
cache:
  directories:
  - $HOME/.local/share/renv
  - $TRAVIS_BUILD_DIR/renv/library

install:
  - Rscript -e "if (!requireNamespace('renv', quietly = TRUE)) install.packages('renv')"
  - Rscript -e "renv::restore()"
  
script:
  - Rscript -e '<your-build-action>'
```

Note that we provide both `install` and `script` steps, as we want to
override the default behaviors provided by Travis for R (which might
attempt to install different version of R packages than what is currently
encoded in `renv.lock`). See
https://docs.travis-ci.com/user/languages/r/#customizing-the-travis-build-steps
for more details.

It's also possible to override the package repository used during restore by
setting the `RENV_CONFIG_REPOS_OVERRIDE` environment variable. For example:

```
env:
  global:
    - RENV_CONFIG_REPOS_OVERRIDE=<cran>
```

replacing `<cran>` with your desired R package repository. This can also be
accomplished in a similar way by setting:

```
options(renv.config.repos.override = <...>)
```

but it is generally more ergonomic to set the associated environment variable.
(See `?config` for more details.) This can be useful if you'd like to, for
example, enforce the usage of a [MRAN](https://mran.microsoft.com) checkpoint
during restore, or another similarly-equipped repository.

See <https://docs.travis-ci.com/user/caching> for more details on how Travis
manages caching.


## GitLab CI

The following template can be used as a base when using `renv` with
[GitLab CI][gitlab-ci]:

```
variables:
  RENV_CONFIG_REPOS_OVERRIDE: "http://cran.r-project.org"
  RENV_PATHS_CACHE: ${CI_PROJECT_DIR}/cache
  RENV_PATHS_LIBRARY: ${CI_PROJECT_DIR}/renv/library

cache:
  key: ${CI_JOB_NAME}
  paths:
    - ${RENV_PATHS_CACHE}
    - ${RENV_PATHS_LIBRARY}

before_script:
  - < ... other pre-deploy steps ... >
  - Rscript -e "if (!requireNamespace('renv', quietly = TRUE)) install.packages('renv')"
  - Rscript -e "renv::restore()"
  
```


[appveyor]: https://www.appveyor.com/
[gitlab-ci]: https://about.gitlab.com/features/continuous-integration/
[github-actions]: https://github.com/features/actions
[github-actions-renv]: https://github.com/actions/cache/blob/main/examples.md#r---renv
[travis-ci]: https://www.travis-ci.com/
