R Debugger installs statistics

R Debugger

This extension adds debugging capabilities for the R programming language to Visual Studio Code and depends on the R package vscDebugger (documentation). For further R support in VS Code see vscode-R.

Features

The debugger includes the following features: 1. Run and debug R Code by launching a new R process or attaching to a running one. 2. View scopes and variables of the currently selected stack frame. For many variables it is also possible to assign a new value to the variable or individual entries/attributes in this view. 3. Add watch expressions that are evaluated in the selected stack frame on each breakpoint/step. 4. View and browse through the call stack when execution is paused. 5. Set breakpoints and break on errors. 6. Control the program flow using *step*, *step in*, *step out*, *continue*. 7. Output generated by the program is printed to the debug console (filtering out text printed by the browser itself). 8. The debugger adds a modified version of print, cat, message, and str that also print a link to the file and line where the text was printed. 9. The debug console allows the execution of arbitrary R code in the currently selected stack frame.

Installation

The latest version of the VS Code extension can be installed from the marketplace. After installing the extension, the R package can be installed or updated using the command r.debugger.installOrUpdateRPackage. If your R path is neither in the Windows registry nor the PATH environment variable, make sure to provide a valid path to the R executable in the setting r.rpath.xxx.

If the package installation does not work, the command r.debugger.installRPackage will attempt to install from a release on r-universe.dev, the source code on GitHub, and a GitHub Release (in that order). You can also install the package manually using

or from artifacts on the releases site.

If you want to install a development version of the extension, it can be installed from the .vsix-files found in the artifacts of the GitHub Actions Workflows.

Using the Debugger

Launch Mode

• Press F5 and select R Debugger as debugger. With the default launch configuration, the debugger will start a new R session. • To run a file, focus the file in the editor and press F5 (or the continue button in the debug controls) • Output will be printed to the debug console, expressions entered into the debug console are evaluated in the currently active frame • During debugging in the global workspace it is often necessary to click the dummy frame in the callstack labelled 'Global Workspace' to see the variables in .GlobalEnv.

Attach Mode

• Start R in a terminal • Load library(vscDebugger) • Call .vsc.listen() • Start the debugger with launch configuration including "request":"attach", e.g.:

Configuration

For a detailed explanation of possible launch config entries and other settings, see Configuration.

Encoding issues on windows

Due to some changes in v0.5.0 concerning the communication between this extension and the R package vscDebugger, combined with the way non-utf-8 encodings are handled in R, there might be some problems with this extension on Windows. However, as of R-version 4.2.2, R can handle UTF-8 encoded communication on Windows much better. To avoid these issues, it is recommended to update R to at least v4.2.2 and use the latest version of this extension and the related R package.

How it works

The debugger works as follows:

• An R process is started inside a child process • The R package vscDebugger is loaded. • The Debugger starts and controls R programs by sending input to stdin of the child process • After each step, function call etc., the debugger calls functions from the package vscDebugger to get info about the stack/variables

The output of the R process is read and parsed as follows:

• Information sent by functions from vscDebugger is encoded as json and sent via a TCP socket. These lines are parsed by the VS Code extension and not shown to the user. • Information printed by the browser() function is parsed and used to update the source file/line highlighted inside VS Code. These lines are also hidden from the user. • Everything else is printed to the debug console

Debugging R Packages

Packages can now be debugged using load_all from pkgload. To do so, it is required to install pkgload (part of devtools). By default, load_all will be masked by a modified version that automatically sets breakpoints in the loaded package and attaches the modified versions of print, cat, message. To always load a package when launching a debug session, you can specify an array of paths in the launch config entry "loadPackages". This is done (for the currently opened package) in the example debug config "Debug R-Package".

Packages with a more complicated installation that might not be compatible with load_all can also be debugged. For this to work, the proper source information must be retained during the installation of the package (check attr(attr(FUNCTION_NAME, 'srcref'), 'srcfile') for some function from the package):

• The package must be installed from source code (not CRAN or .tar.gz) • The flag --with-keep.source should be set • Extensions containing C code might cause problems. Sometimes it helps to install the package using devtools::install(quick=FALSE, ...) to compile the binaries and again with devtools::install(quick=TRUE, ...) to retain the source information.

The packages that are being debugged then need to be specified in the launch config as follows:

To overwrite the print/cat/message functions for an individual package, they need to be explicitly assigned somewhere in the package:

This assignment can be overwritten by the debugger with .vsc.print/.vsc.cat/.vsc.message, but has no effect when not using the debugger.

Troubleshooting

For troubleshooting info, see Troubleshooting

Contributing…

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