Changes in R

We give a selection of the most important changes in R 4.2.0 and of subsequent bug fixes for the Windows port of R. We also provide statistics on source code commits.

1 R 4.2.0 selected changes

R 4.2.0 (codename “Vigorous Calisthenics”) was released on 2022-04-22. The December 2021 (13/2) issue of the R Journal provided a selection of the most important changes in that release that were already settled at that time, including:

• R on Windows uses UTF-8 as the native encoding, uses the new Universal C Runtime (UCRT) and a new toolchain (Rtools42).
• R on Windows changed the default library location and the default installation location for user-only installation to match current Windows conventions.
• Support for isolated groups, compositing operators, affine transformations, and stroking and filling paths has been added to the R graphics engine.
• R now provides an R-level interface for hash tables.

A selection of the remaining important R 4.2.0 changes is provided here.

• The HTML help system has several new features: LaTeX-like math can be typeset using either KaTeX or MathJax, usage and example code is highlighted using Prism, and for dynamic help the output of examples and demos can be shown within the browser if the knitr package is installed. (These features can be disabled by setting the environment variable _R_HELP_ENABLE_ENHANCED_HTML_ to a false value.) The HTML help system now uses HTML5, the current HTML standard, which in particular helps to facilitate some of the enhancements described above. Considerable effort was put into ensuring valid HTML5 output. The old validation toolchain could not handle HTML5, so a new one was created based on HTML Tidy and integrated into the tools package. R CMD check can now optionally (but included in –as-cran) validate the package HTML help files.

  See https://blog.r-project.org/2022/04/08/enhancements-to-html-documentation/ for more information.

• Calling if() or while() with a condition of length greater than one now gives an error rather than a warning. Consequently, environment variable _R_CHECK_LENGTH_1_CONDITION_ no longer has any effect. Similarly, calling && or || with either argument of length greater than one now gives a warning. In R 4.3.0, it will give an error, and environment variable _R_CHECK_LENGTH_1_LOGIC2_ will no longer have any effect.

• The grid package now allows the user to specify a vector of pattern fills. The fill argument to gpar() accepts a list of gradients and/or patterns and the functions linearGradient(), radialGradient(), and pattern() have a new group argument. Finally, points grobs (data symbols) can now also have a pattern fill. See https://blog.r-project.org/2022/06/09/vectorised-patterns-in-r-graphics/ for more information.

• In lhs |> rhs expressions using the native pipe operator it is now possible to use a named argument with the placeholder _ in the rhs call to specify where the lhs is to be inserted. The placeholder can only appear once on the rhs.

• On Windows, download.file(method = "auto") and url(method = "default") now follow Unix in using "libcurl" for all except file:// URIs. This impacts, for example, updating of R packages (HTTPS downloads). Most users should not notice, but an additional proxy setup may be required (see help("download.file")). Also, "libcurl" is by the decision of the library authors stricter in checking certificate revocation than the previous "wininet" method. This brings more security, but also may cause trouble with some corporate HTTPS MITM proxies, which filter HTTPS traffic. R-patched (to become R 4.2.2) has a work-around via environment variable R_LIBCURL_SSL_REVOKE_BEST_EFFORT.

2 R 4.2.1 and R-patched changes on Windows

R 4.2.0 on Windows switched to UTF-8 as the native encoding and to UCRT as the Windows runtime. R is an early adopter of UCRT in the open-source community of projects compiled using free and open-source compilers, and particularly an early adopter of UTF-8 as the native encoding on Windows, hence this came with considerable effort and risk of bugs. Hence, testing using CRAN package checks has been in place for over a year before the release (and 9 months of that time in parallel to the usual CRAN checks when R-devel still used MSVCRT as the C runtime).

Still, some issues not covered by such tests, mostly in interactive use and Rgui, have been reported by users after the 4.2 release and have been fixed in R-patched. R users on Windows should update to the latest available patch version.

Selected fixes in R 4.2.1:

• Accent keys now work in GraphApp Unicode windows, which are used by Rgui whenever running in a multi-byte locale (so also in UTF-8), hence fixing a regression for users of systems where R 4.1 used a single-byte locale. This was one of the bugs already present in GraphApp, but never reported before, e.g., by users of other multi-byte locales.
• Text injection from external applications via SendInput now works in GraphApp Unicode windows, fixing a regression in R 4.2.0 for Rgui users of systems where R 4.1 used a single-byte locale but R 4.2.0 uses UTF-8. Text injection is used via applications such as Dasher, which helps people with hand impairment to enter text, and by general GUIs that prefer to use a standalone Rgui window over embedding R. This was another old bug in GraphApp impacting multi-byte locales. Some other applications injecting text via sending Windows window messages such as WM_CHAR directly to Rgui should switch to injection via SendInput, which is the proper injection method on Windows and the switch should not be difficult. Allowing injection via WM_CHAR even in a multi-byte locale would require too big changes in GraphApp.
• A regression in writing to the clipboard connection has been fixed. That code had to be rewritten for the UTF-8 transition, but the new version had a bug which prevented writing text in consecutive operations.
• getlocale has been fixed to also work with strict checking of invalid arguments to the C runtime. These are normally disabled in applications built using Rtools, but it impacted embedded use in RStudio with the rJava package, causing crashes by default. This issue was related to switching to UCRT, which is stricter in checking the validity of function arguments (it was not directly related to UTF-8 nor the locale).
• The script editor in Rgui has been fixed to work with UTF-8: some operations (such as running a line of code from the editor in the R console) before did not work with non-ASCII characters, with a regression in R 4.2.0 (in earlier versions one could work at least with non-ASCII characters representable in the current locale). These issues are related to at least surprising behavior of the underlying Windows component used for the editor with UTF-8 as the native (ANSI) encoding: one would think that no change would be needed for the transition from a non-UTF-8 native encoding to UTF-8 here. Users of the script editor have to convert their scripts with non-ASCII characters to UTF-8 before reading them in R 4.2.1 or newer (on recent Windows where UTF-8 is used), and they should upgrade to R 4.2.2 when it is available.

Selected fixes in R-patched, to become R 4.2.2:

• Rterm support for Alt+xxx sequences has been fixed to produce the corresponding character (only) once. This fixes pasting text that includes tilde on Italian keyboard; without the fix, tilde may appear twice, depending on the Windows console program used. This was a regression introduced by an earlier rewrite of Rterm for supporting multi-width characters. That change was part of the transition to UTF-8, but already included in R 4.1.
• Find and replace operations work again in the script editor in Rgui.

The bug reports have revealed that Rgui is frequently used, including by users with visual or hand impairments who find Rgui working well with assistive technologies.

The bugs were fixed promptly in R-patched. Impacted users may install a snapshot of R-patched in case waiting for the next release would be too limiting.

3 R 4.2.0 code statistics

From the source code Subversion repository, the overall change between May 18, 2021 and April 22, 2022 (so between R 4.1.0 and R 4.2.0) was: 29,000 added lines, 20,000 deleted lines and 900 changed files. This is rounded to thousands/hundreds and excludes changes to common generated files, bulk re-organizations, etc. (translations, parsers, Autoconf, LAPACK, R Journal bibliography, test outputs, Unicode tables, incorporated M4 macros, BLAS, KaTeX files). This is about 10% fewer additions and changed files and about 43% more deletions than between R 4.0.0 and R 4.1.0, see News and Notes from the June 2021 issue of the R Journal.

Figure 1 shows commits by month and weekday, respectively, counting line-based changes in individual commits, excluding the files as above. The statistics are computed the same way as in the June 2021 issue, hence allowing direct comparisons. However, monthly statistics are impacted by the release date which varies across versions, so the numbers for April and May are somewhat biased. The statistics cover code directly committed to the trunk, plus commits from the merged branches R-groups, R-vecpat. R-ucrt and R-structure. Statistics are based on the dates of the original commits in the branches, which includes commits from April 2021 (R-groups).

Figure 1: Commit statistics by month (left) and weekday (right) during R 4.2.0 development. *Counts for April 2021 represent early work on the R-groups branch. May 2021 and April 2022 are partial months impacted by the release dates.

4 Acknowledgements

Tomas Kalibera’s work on the article and R development has received funding from the Czech Ministry of Education, Youth and Sports from the Czech Operational Programme Research, Development, and Education, under grant agreement No.CZ.02.1.01/0.0/0.0/15_003/0000421, from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme, under grant agreement No. 695412, and from the National Science Foundation award 1925644.

CRAN packages used

knitr, rJava

CRAN Task Views implied by cited packages

HighPerformanceComputing, ReproducibleResearch

Note

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