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packageDescription: Package Description

packageDescription

R Documentation

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

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