src/library/base/R/autoload.R

#  File src/library/base/R/autoload.R
#  Part of the R package, https://www.R-project.org
#
#  Copyright (C) 1995-2012 The R Core Team
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  A copy of the GNU General Public License is available at
#  https://www.R-project.org/Licenses/

autoload <- function(name, package, reset=FALSE, ...)
{
    if (!reset && exists(name, envir = .GlobalEnv, inherits = FALSE))
	stop("an object with that name already exists")
    m <- match.call()
    m[[1L]] <- as.name("list")
    newcall <- eval(m, parent.frame())
    newcall <- as.call(c(as.name("autoloader"), newcall))
    newcall$reset <- NULL
    if (is.na(match(package, .Autoloaded)))
	assign(".Autoloaded", c(package, .Autoloaded), envir =.AutoloadEnv)
    do.call("delayedAssign", list(name, newcall, .GlobalEnv, .AutoloadEnv))
    ## no longer return the result, which is a promise
    invisible()
}

autoloader <- function (name, package, ...)
{
    name <- paste0(name, "")
    rm(list = name, envir = .AutoloadEnv, inherits = FALSE)
    m <- match.call()
    m$name <- NULL
    m[[1L]] <- as.name("library")
    ## load the package
    eval(m, .GlobalEnv)
    ## reset the autoloader
    autoload(name, package, reset = TRUE, ...)
    ## reevaluate the object
    where <- match(paste0("package:", package), search())
    if (exists(name, where = where, inherits = FALSE))
	eval(as.name(name), as.environment(where))
    else
	stop(gettextf("autoloader did not find '%s' in '%s'", name, package),
             domain = NA)
}