packageDescription Package Description

Description

Parses and returns the ‘DESCRIPTION’ file of a package as a "packageDescription".

Utility functions return (transformed) parts of that.

Usage

packageDescription(pkg, lib.loc = NULL, fields = NULL,
                   drop = TRUE, encoding = "")
packageVersion(pkg, lib.loc = NULL)
packageDate(pkg, lib.loc = NULL,
            date.fields = c("Date", "Packaged", "Date/Publication", "Built"),
            tryFormats = c("%Y-%m-%d", "%Y/%m/%d", "%D", "%m/%d/%y"),
            desc = packageDescription(pkg, lib.loc=lib.loc, fields=date.fields))
asDateBuilt(built)

Arguments

pkg	a character string with the package name.
lib.loc	a character vector of directory names of R libraries, or NULL. The default value of NULL corresponds to all libraries currently known. If the default is used, the loaded packages and namespaces are searched before the libraries.
fields	a character vector giving the tags of fields to return (if other fields occur in the file they are ignored).
drop	If TRUE and the length of fields is 1, then a single character string with the value of the respective field is returned instead of an object of class "packageDescription".
encoding	If there is an Encoding field, to what encoding should re-encoding be attempted? If NA, no re-encoding. The other values are as used by iconv, so the default "" indicates the encoding of the current locale.
date.fields	character vector of field tags to be tried. The first for which as.Date(.) is not NA will be returned. (Partly experimental, see Note.)
tryFormats	date formats to try, see as.Date.character().
desc	optionally, a named list with components named from date.fields; where the default is fine, a complete packageDescription() maybe specified as well.
built	for asDateBuilt(), a character string as from packageDescription(*, fields="Built").

Details

A package will not be ‘found’ unless it has a ‘DESCRIPTION’ file which contains a valid Version field. Different warnings are given when no package directory is found and when there is a suitable directory but no valid ‘DESCRIPTION’ file.

An attached environment named to look like a package (e.g., package:utils2) will be ignored.

packageVersion() is a convenience shortcut, allowing things like if (packageVersion("MASS") < "7.3") { do.things } .

For packageDate(), if desc is valid, both pkg and lib.loc are not made use of.

Value

If a ‘DESCRIPTION’ file for the given package is found and can successfully be read, packageDescription returns an object of class "packageDescription", which is a named list with the values of the (given) fields as elements and the tags as names, unless drop = TRUE.

If parsing the ‘DESCRIPTION’ file was not successful, it returns a named list of NAs with the field tags as names if fields is not null, and NA otherwise.

packageVersion() returns a (length-one) object of class "package_version".

packageDate() will return a "Date" object from as.Date() or NA.

asDateBuilt(built) returns a "Date" object or signals an error if built is invalid.

Note

The default behavior of packageDate(), notably for date.fields, is somewhat experimental and may change. Using date.fields = <string> single

See Also

read.dcf

Examples

packageDescription("stats")
packageDescription("stats", fields = c("Package", "Version"))

packageDescription("stats", fields = "Version")
packageDescription("stats", fields = "Version", drop = FALSE)

if(packageVersion("MASS") < "7.3.29")
  message("you need to update 'MASS'")

pu <- packageDate("utils")
str(pu)
stopifnot(identical(pu, packageDate(desc = packageDescription("utils"))),
          identical(pu, packageDate("stats"))) # as "utils" and "stats" are
                                   # both 'base R' and "Built" at same time