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

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


## Development

Often, R packages will have other R packages as dependencies. For this, one must
declare their R package dependencies within the package `DESCRIPTION` file. If
you want to prepare your environment for package development, you can use:

```
renv::install()
```

to install the packages as declared in the package's `DESCRIPTION` file. This
action is roughly analogous to `remotes::install_deps()`.

If you're developing a package that you intend to release to CRAN, then you
likely want to build and test your package against the latest versions of your
dependencies as available on CRAN. For this, you should consider using:

```
renv::update()
```

to ensure your package dependencies are up-to-date, as appropriate.


## Isolation

Normally, a package under development should be tested against the
latest-available versions of its dependencies on CRAN. However, in some cases,
you may need to ensure your package is compatible with other packages also
currently under development.

In these cases, the `renv` project library can be useful -- you can install the
development version(s) of your dependencies into the project library, without
worrying about clobbering any packages already installed in your user library.

In these cases, you can declare your development dependencies using the
`Remotes` field of the `DESCRIPTION` file; e.g.

```
Remotes:
  r-lib/ggplot2
```

and `renv::install()` will parse that remotes declaration and retrieve the
requested package. See the `remotes` vignette,
[Dependency resolution for R package development][dependencies],
for more details.


## Testing

While developing your package, you may want to use a continuous integration
service (such as [Travis CI](https://www.travis-ci.org/)) to build and test
your package remotely. You can use `renv` to help facilitate this testing --
see the [Continuous Integration][ci] vignette for more information. In
particular, clever use of the `renv` cache can help save time that might
normally be spent on package installation.


## R CMD build and the Project Library

By default, when building a package tarball, R will copy all files within the
package directory to a temporary build directory before building the package.
Unfortunately, this also implies copying the `renv` library. When that library
is large, this can dramatically increase the amount of time it takes to build
your package.

One way to resolve this issue is to force `renv` to use a library path that
lives outside of your project. For example, you might set the following in
a start-up `.Renviron` file:

```
RENV_PATHS_LIBRARY_ROOT = ~/.renv/library
```

`renv` will then form library paths within this directory.

By default, library paths will be formed using the project name, alongside a
unique identifier generated from the full project path. These paths are of
the form:

```
<name>-<id>
```

If you'd prefer to omit the `<id>`, then you can set the environment variable:

```
RENV_PATHS_LIBRARY_ROOT_ASIS = TRUE
```

to instruct `renv` to forego the use of an identifier.




[ci]: https://CRAN.R-project.org/package=renv/vignettes/ci.html
[dependencies]: https://CRAN.R-project.org/package=remotes/vignettes/dependencies.html

