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load_all() loads a package. It roughly simulates what happens when a package is installed and loaded with library(), without having to first install the package. It:

  • Loads all data files in data/. See load_data() for more details.

  • Sources all R files in the R directory, storing results in environment that behaves like a regular package namespace. See load_code() for more details.

  • Adds a shim from system.file() to shim_system.file() in the imports environment of the package. This ensures that system.file() works with both development and installed packages despite their differing directory structures.

  • Adds shims from help() and ? to shim_help() and shim_question() to make it easier to preview development documentation.

  • Compiles any C, C++, or Fortran code in the src/ directory and connects the generated DLL into R. See pkgbuild::compile_dll() for more details.

  • Loads any compiled translations in inst/po.

  • Runs .onAttach(), .onLoad() and .onUnload() functions at the correct times.

  • If you use testthat, will load all test helpers so you can access them interactively. devtools sets the DEVTOOLS_LOAD environment variable to "true" to let you check whether the helpers are run during package loading.

is_loading() returns TRUE when it is called while load_all() is running. This may be useful e.g. in .onLoad hooks.


  path = ".",
  reset = TRUE,
  compile = NA,
  attach = TRUE,
  export_all = TRUE,
  export_imports = export_all,
  helpers = TRUE,
  attach_testthat = uses_testthat(path),
  quiet = NULL,
  recompile = FALSE,
  warn_conflicts = TRUE

is_loading(pkg = NULL)



Path to a package, or within a package.


clear package environment and reset file cache before loading any pieces of the package. This largely equivalent to running unload(), however the old namespaces are not completely removed and no .onUnload() hooks are called. Use reset = FALSE may be faster for large code bases, but is a significantly less accurate approximation.


If TRUE always recompiles the package; if NA recompiles if needed (as determined by pkgbuild::needs_compile()); if FALSE, never recompiles.


Whether to attach a package environment to the search path. If FALSE load_all() behaves like loadNamespace(). If TRUE (the default), it behaves like library(). If FALSE, the export_all, export_imports, and helpers arguments have no effect.


If TRUE (the default), export all objects. If FALSE, export only the objects that are listed as exports in the NAMESPACE file.


If TRUE (the default), export all objects that are imported by the package. If FALSE export only objects defined in the package.


if TRUE loads testthat test helpers.


If TRUE, attach testthat to the search path, which more closely mimics the environment within test files.


if TRUE suppresses output from this function.


DEPRECATED. force a recompile of DLL from source code, if present. This is equivalent to running pkgbuild::clean_dll() before load_all()


If TRUE, issues a warning if a function in the global environment masks a function in the package. This can happen when you accidentally source a .R file, rather than using load_all(), or if you define a function directly in the R console. This is frustrating to debug, as it feels like the changes you make to the package source aren't having the expected effect.


If supplied, is_loading() only returns TRUE if the package being loaded is pkg.

Differences to regular loading

load_all() tries its best to reproduce the behaviour of loadNamespace() and library(). However it deviates from normal package loading in several ways.

  • load_all() doesn't install the package to a library, so system.file() doesn't work. pkgload fixes this for the package itself installing a shim, shim_system.file(). However, this shim is not visible to third party packages, so they will fail if they attempt to find files within your package. One potential workaround is to use fs::path_package() instead of system.file(), since that understands the mechanisms that devtools uses to load packages.

  • load_all() loads all packages referenced in Imports at load time, but loadNamespace() and library() only load package dependencies as they are needed.

  • load_all() copies all objects (not just the ones listed as exports) into the package environment. This is useful during development because it makes internal objects easy to access. To export only the objects listed as exports, use export_all = FALSE. This more closely simulates behavior when loading an installed package with library(), and can be useful for checking for missing exports.


if (FALSE) {
# Load the package in the current directory

# Running again loads changed files

# With reset=TRUE, unload and reload the package for a clean start
load_all("./", TRUE)

# With export_all=FALSE, only objects listed as exports in NAMESPACE
# are exported
load_all("./", export_all = FALSE)