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##### Hannah Frick, Data Scientist

We are excited to annouce that the goodpractice package is now available on CRAN. The package gives advice about good practices when building R packages. Advice includes functions and syntax to avoid, package structure, code complexity, code formatting, etc.

You can install the CRAN version via

install.packages("goodpractice")

## Building R packages

Building an R package is a great way of encapsulating code, documentation and data in a single testable and easily distributable unit.

For a package to be distributed via CRAN, it needs to pass a set of checks implemented in R CMD check, such as: Is there minimal documentation, e.g., are all arguments of exported functions documented? Are all dependencies declared?

These checks are helpful in developing a solid R package but they don’t check for several other good practices. For example, a package does not need to contain any tests but is it good practice to include some. Following a coding standard helps readability. Avoiding overly complex functions reduces the risk of bugs. Including an URL for bug reports lets people more easily report bugs if they find any.

### What the goodpractice package does

Tools for automatically checking several of the above mentioned aspects already exist and the goodpractice package bundles the checks from rcmdcheck with code coverage through the covr package, source code linting via the lintr package and cyclompatic complexity via the cyclocomp package and augments it with some further checks on good practice for R package development such as avoiding T and F in favour of TRUE and FALSE. It provides advice on which practices to follow and which to avoid.

You can use goodpractice checks as a reminder for you and your collegues – and if you have custom checks to run, you can make goodpractice run those as well!

## How to use goodpractice

The main fuction goodpractice() (and its alias gp()) takes the path to the source code of a package as its first argument. The goodpractice package contains the source for a simple package which violates some good practices. We’ll use this for the examples.

library(goodpractice)

# get path to example package
pkg_path <- system.file("bad1", package = "goodpractice")

# run gp() on it
g <- gp(pkg_path)
#> Preparing: covr
#> Warning in MYPREPS[[prep]](state, quiet = quiet): Prep step for test
#> coverage failed.
#> Preparing: cyclocomp
#> Skipping 2 packages ahead of CRAN: callr, remotes
#> Installing 1 packages: stringr
#>
#>   There is a binary version available but the source version is
#>   later:
#>         binary source needs_compilation
#> stringr  1.3.0  1.3.1             FALSE
#> installing the source package 'stringr'
#> Preparing: description
#> Preparing: lintr
#> Preparing: namespace
#> Preparing: rcmdcheck

# show the result
g
#> ── GP badpackage ──────────────────────────────────────────────────────────
#>
#> It is good practice to
#>
#>   ✖ not use "Depends" in DESCRIPTION, as it can cause name
#>     clashes, and poor interaction with other packages. Use
#>   ✖ omit "Date" in DESCRIPTION. It is not required and it gets
#>     invalid quite often. A build date will be added to the package
#>     when you perform R CMD build on it.
#>   ✖ add a "URL" field to DESCRIPTION. It helps users find
#>     information about your package online. If your package does
#>     not have a homepage, add an URL to GitHub, or the CRAN package
#>     package page.
#>   ✖ add a "BugReports" field to DESCRIPTION, and point it to a bug
#>     tracker. Many online code hosting services provide bug
#>     etc.
#>   ✖ omit trailing semicolons from code lines. They are not needed
#>     and most R coding standards forbid them
#>
#>     R/semicolons.R:4:30
#>     R/semicolons.R:5:29
#>     R/semicolons.R:9:38
#>
#>   ✖ not import packages as a whole, as this can cause name clashes
#>     between the imported packages. Instead, import only the
#>     specific functions you need.
#>   ✖ fix this R CMD check ERROR: VignetteBuilder package not
#>     declared: ‘knitr’ See section ‘The DESCRIPTION file’ in the
#>     ‘Writing R Extensions’ manual.
#>   ✖ avoid 'T' and 'F', as they are just variables which are set to
#>     the logicals 'TRUE' and 'FALSE' by default, but are not
#>     reserved words and hence can be overwritten by the user.
#>     Hence, one should always use 'TRUE' and 'FALSE' for the
#>     logicals.
#>
#>     R/tf.R:NA:NA
#>     R/tf.R:NA:NA
#>     R/tf.R:NA:NA
#>     R/tf.R:NA:NA
#>     R/tf.R:NA:NA
#>     ... and 4 more lines
#>
#> ───────────────────────────────────────────────────────────────────────────

So with this package, we’ve done a few things in the DESCRIPTION file for which there are reasons not to do them, have unnecessary trailing semicolons in the code and used T and F for TRUE and FALSE. The output of gp() will tell you what isn’t considered good practice out of what you have already written. If that is in the R code itself, it will also point you to the location of your faux-pas. In general, the messages are supposed to not only point out to you what you might want to avoid but also why.

### Custom checks

The above example tries to run all 230 checks available, to see the full list use all_checks(). You can customise the set of checks run by selecting only those default checks you are intersted in and by adding your own checks.

If you only want to run a subset of the checks, e.g., just the check on the URL field in the DESCRIPTION, you can specify the checks by name:

# what is the name of the check?
grep("url", all_checks(), value = TRUE)
#> [1] "description_url"

# run only this check
gp(pkg_path, checks = "description_url")
#> Preparing: description
#> ── GP badpackage ──────────────────────────────────────────────────────────
#>
#> It is good practice to
#>
#>   ✖ add a "URL" field to DESCRIPTION. It helps users find
#>     information about your package online. If your package does
#>     not have a homepage, add an URL to GitHub, or the CRAN package
#>     package page.
#> ───────────────────────────────────────────────────────────────────────────

Additional checks can be used in gp() via the extra_checks argument. This should be a named list of check objects as returned by the make_check() function.

# make a simple version of the T/F check
check_simple_tf <- make_check(

description = "TRUE and FALSE is used, not T and F",
gp = "avoid 'T' and 'F', use 'TRUE' and 'FALSE' instead.",
check = function(state) {
length(tools::checkTnF(dir = state\$path)) == 0
}
)

gp(pkg_path, checks = c("description_url", "simple_tf"),
extra_checks = list(simple_tf = check_simple_tf))
#> Preparing: description
#> ── GP badpackage ──────────────────────────────────────────────────────────
#>
#> It is good practice to
#>
#>   ✖ add a "URL" field to DESCRIPTION. It helps users find
#>     information about your package online. If your package does
#>     not have a homepage, add an URL to GitHub, or the CRAN package
#>     package page.
#>   ✖ avoid 'T' and 'F', use 'TRUE' and 'FALSE' instead.
#> ───────────────────────────────────────────────────────────────────────────

For more details on creating custom checks, please see the vignette Custom Checks.

## Acknowledgements

This package was written by Gábor Csárdi with contributions by Noam Ross, Neal Fultz, Douglas Ashton, Marcel Ramos, Joseph Stachelek, and myself. Special thanks for the input and feedback to the rOpenSci leadership team and community as well as everybody who opened issues!

## Feedback

If you have any feedback, please consider opening an issue on GitHub.