• Stars
    star
    173
  • Rank 219,479 (Top 5 %)
  • Language
    R
  • License
    Other
  • Created over 9 years ago
  • Updated 2 months ago

Reviews

There are no reviews yet. Be the first to send feedback to the community and the maintainers!

Repository Details

Methods For Temporarily Modifying Global State

withr - run code ‘with’ modified state

Codecov test coverage CRAN Version R-CMD-check

Overview

A set of functions to run code with safely and temporarily modified global state, withr makes working with the global state, i.e. side effects, less error-prone.

Pure functions, such as the sum() function, are easy to understand and reason about: they always map the same input to the same output and have no other impact on the workspace. In other words, pure functions have no side effects: they are not affected by, nor do they affect, the global state in any way apart from the value they return.

The behavior of some functions is affected by the global state. Consider the read.csv() function: it takes a filename as an input and returns the contents as an output. In this case, the output depends on the contents of the file; i.e. the output is affected by the global state. Functions like this deal with side effects.

The purpose of the withr package is to help you manage side effects in your code. You may want to run code with secret information, such as an API key, that you store as an environment variable. You may also want to run code with certain options, with a given random-seed, or with a particular working-directory.

The withr package helps you manage these situations, and more, by providing functions to modify the global state temporarily, and safely. These functions modify one of the global settings for duration of a block of code, then automatically reset it after the block is completed.

Installation

#Install the latest version with:
install.packages("withr")

Many of these functions were originally a part of the devtools package, this provides a simple package with limited dependencies to provide access to these functions.

  • with_collate() / local_collate() - collation order
  • with_dir() / local_dir() - working directory
  • with_envvar() / local_envvar() - environment variables
  • with_libpaths() / local_libpaths() - library paths
  • with_locale() / local_locale() - any locale setting
  • with_makevars() / local_makevars() / set_makevars() - makevars variables
  • with_options() / local_options() - options
  • with_par() / local_par() - graphics parameters
  • with_path() / local_path() - PATH environment variable
  • with_*() and local_*() functions for the built in R devices, bmp, cairo_pdf, cairo_ps, pdf, postscript, svg, tiff, xfig, png, jpeg.
  • with_connection() / local_connection() - R file connections
  • with_db_connection() / local_db_connection() - DB connections
  • with_package() / local_package(), with_namespace() / local_namespace() and with_environment() / local_environment() - to run code with modified object search paths.
  • with_tempfile() / local_tempfile() - create and clean up a temp file.
  • with_file() / local_file() - create and clean up a normal file.
  • with_message_sink() / local_message_sink() - divert message
  • with_output_sink() / local_output_sink() - divert output
  • with_preserve_seed() / with_seed()- specify seeds
  • with_temp_libpaths() / local_temp_libpaths() - library paths
  • defer() / defer_parent() - defer
  • with_timezone() / local_timezone() - timezones
  • with_rng_version() / local_rng_version() - random number generation version

Usage

There are two sets of functions, those prefixed with with_ and those with local_. The former reset their state as soon as the code argument has been evaluated. The latter reset when they reach the end of their scope, usually at the end of a function body.

par("col" = "black")
my_plot <- function(new) {
  with_par(list(col = "red", pch = 19),
    plot(mtcars$hp, mtcars$wt)
  )
  par("col")
}
my_plot()

#> [1] "black"
par("col")
#> [1] "black"

f <- function(x) {
  local_envvar(c("WITHR" = 2))
  Sys.getenv("WITHR")
}

f()
#> [1] "2"
Sys.getenv("WITHR")
#> [1] ""

There are also with_() and local_() functions to construct new with_* and local_* functions if needed.

Sys.getenv("WITHR")
#> [1] ""
with_envvar(c("WITHR" = 2), Sys.getenv("WITHR"))
#> [1] "2"
Sys.getenv("WITHR")
#> [1] ""

with_envvar(c("A" = 1),
  with_envvar(c("A" = 2), action = "suffix", Sys.getenv("A"))
)
#> [1] "1 2"

See Also

More Repositories

1

devtools

Tools to make an R developer's life easier
R
2,392
star
2

lintr

Static Code Analysis for R
R
1,189
star
3

httr

httr: a friendly http package for R
R
984
star
4

actions

GitHub Actions for the R community
TypeScript
948
star
5

testthat

An R 📦 to make testing 😀
R
875
star
6

usethis

Set up commonly used 📦 components
R
842
star
7

pkgdown

Generate static html documentation for an R package
R
714
star
8

styler

Non-invasive pretty printing of R code
R
706
star
9

pak

A fresh approach to package installation
C
652
star
10

cli

Tools for making beautiful & useful command line interfaces
R
635
star
11

rig

The R Installation Manager
Rust
609
star
12

roxygen2

Generate R package documentation from inline R comments
R
590
star
13

rlang

Low-level API for programming with R
R
498
star
14

progress

Progress bar in your R terminal
R
463
star
15

here

A simpler way to find your files
R
410
star
16

R6

Encapsulated object-oriented programming for R
R
405
star
17

scales

Tools for ggplot2 scales
R
392
star
18

fs

Provide cross platform file operations based on libuv.
C
362
star
19

rex

Friendly regular expressions for R.
R
331
star
20

covr

Test coverage reports for R
R
331
star
21

crayon

🖍️ R package for colored terminal output — now superseded by cli
R
325
star
22

remotes

Install R packages from GitHub, GitLab, Bitbucket, git, svn repositories, URLs
R
325
star
23

memoise

Easy memoisation for R
R
315
star
24

lobstr

Understanding complex R objects with tools similar to str()
R
301
star
25

profvis

Visualize R profiling data
JavaScript
297
star
26

callr

Call R from R
R
295
star
27

slider

Sliding Window Functions
R
295
star
28

vctrs

Generic programming with typed R vectors
C
284
star
29

waldo

Find differences between R objects
R
275
star
30

zeallot

Variable assignment with zeal! (or multiple, unpacking, and destructuring assignment in R)
R
253
star
31

conflicted

An alternative conflict resolution strategy for R
R
244
star
32

bench

High Precision Timing of R Expressions
R
241
star
33

httr2

Make HTTP requests and process their responses. A modern reimagining of httr.
R
232
star
34

gmailr

Access the Gmail RESTful API from R.
R
229
star
35

processx

Execute and Control Subprocesses from R
R
229
star
36

asciicast

Turn R scripts into terminal screencasts
R
224
star
37

xml2

Bindings to libxml2
R
218
star
38

gh

Minimalistic GitHub API client in R
R
218
star
39

cpp11

cpp11 helps you to interact with R objects using C++ code.
C++
199
star
40

keyring

🔐 Access the system credential store from R
R
191
star
41

vdiffr

Visual regression testing and graphical diffing with testthat
C++
182
star
42

pillar

Format columns with colour
R
179
star
43

svglite

A lightweight svg graphics device for R
C++
179
star
44

ragg

Graphic Devices Based on AGG
C++
172
star
45

hugodown

Make websites with hugo and RMarkdown
R
166
star
46

ymlthis

write YAML for R Markdown, bookdown, blogdown, and more
R
163
star
47

coro

Coroutines for R
R
153
star
48

rprojroot

Finding files in project subdirectories
R
148
star
49

debugme

Easy and efficient debugging for R packages
R
146
star
50

available

Check if a package name is available to use
R
142
star
51

gert

Simple git client for R
C
142
star
52

archive

R bindings to libarchive, supporting a large variety of archive formats
C++
142
star
53

ellipsis

Tools for Working with ...
R
141
star
54

later

Schedule an R function or formula to run after a specified period of time.
C++
136
star
55

itdepends

R
133
star
56

fastmap

Fast map implementation for R
C++
132
star
57

prettyunits

Pretty, human readable formatting of quantities
JavaScript
131
star
58

rray

Simple Arrays
R
130
star
59

isoband

isoband: An R package to generate contour lines and polygons.
C++
130
star
60

tidyselect

A backend for functions taking tidyverse selections
R
123
star
61

desc

Manipulate DESCRIPTION files
R
121
star
62

evaluate

A version of eval for R that returns more information about what happened
R
118
star
63

gargle

Infrastructure for calling Google APIs from R, including auth
R
114
star
64

rcmdcheck

Run R CMD check from R and collect the results
R
113
star
65

tree-sitter-r

R
106
star
66

prettycode

Syntax highlight R code in the terminal
R
101
star
67

sloop

S language OOP ⛵️
R
101
star
68

clock

A Date-Time Library for R
R
100
star
69

mockery

A mocking library for R.
R
99
star
70

revdepcheck

R package reverse dependency checking
R
99
star
71

pkgdepends

R Package Dependency Resolution
R
94
star
72

lifecycle

Manage the life cycle of your exported functions and arguments
R
92
star
73

systemfonts

System Native Font Handling in R
C++
91
star
74

commonmark

High Performance CommonMark and Github Markdown Rendering in R
C
88
star
75

downlit

Syntax Highlighting and Automatic Linking
R
86
star
76

gtable

The layout packages that powers ggplot2
R
86
star
77

askpass

Password Entry for R, Git, and SSH
R
84
star
78

zip

Platform independent zip compression via miniz
C
83
star
79

rappdirs

Find OS-specific directories to store data, caches, and logs. A port of python's AppDirs
R
82
star
80

clisymbols

Unicode symbols for CLI applications, with fallbacks
R
79
star
81

marquee

Markdown Parser and Renderer for R Graphics
C
77
star
82

ps

R package to query, list, manipulate system processes
C
73
star
83

credentials

Tools for Managing SSH and Git Credentials
R
72
star
84

sessioninfo

Print Session Information
R
72
star
85

pkgapi

Create a map of functions for an R package - WORK IN PROGRESS!
R
70
star
86

sodium

R bindings to libsodium
R
69
star
87

roxygen2md

Convert elements of roxygen documentation to markdown
R
67
star
88

backports

Reimplementations of Functions Introduced Since R-3.0.0
R
66
star
89

pkgbuild

Find tools needed to build R packages
R
65
star
90

webfakes

Fake web apps for HTTP testing R packages
C
63
star
91

generics

Common generic methods
R
61
star
92

cliapp

Rich Command Line Applications
R
61
star
93

diffviewer

HTML widget to visually compare files
JavaScript
58
star
94

pkgload

Simulate installing and loading a package
R
58
star
95

cachem

Key-value caches for R
R
57
star
96

liteq

Serverless R message queue using SQLite
R
56
star
97

brio

Basic R Input Output
R
53
star
98

carrier

Create standalone functions for remote execution
R
50
star
99

jose

Javascript Object Signing and Encryption for R
R
48
star
100

urlchecker

Run CRAN URL checks from older versions of R
R
45
star