description: Read, write, update, validate DESCRIPTION files

Description Format Constructors Setting and Querying fields Normalizing Writing it to file Version numbers Dependencies Collate fields Authors URLs Remotes Built Encodings Examples

Description

Read, write, update, validate DESCRIPTION files

Format

An R6 class.

Constructors

There are two ways of creating a description object. The first is reading an already existing DESCRIPTION file; simply give the name of the file as an argument. The default is DESCRIPTION:

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  x <- description$new()
  x2 <- description$new("path/to/DESCRIPTION")

The second way is creating a description object from scratch, supply "!new" as an argument to do this.

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  x3 <- description$new("!new")

The complete API reference:

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description$new(cmd = NULL, file = NULL, text = NULL,
    package = NULL)
cmd:

A command to create a description from scratch. Currently only "!new" is implemented. If it does not start with an exclamation mark, it will be interpreted as a ‘file’ argument.

file:

Name of the DESCRIPTION file to load. If it is a directory, then we assume that it is inside an R package and conduct a search for the package root directory, i.e. the first directory up the tree that contains a DESCRIPTION file. If ‘cmd’, ‘file’, ‘text’ and ‘package’ are all NULL (the default), then the search is started from the working directory. The file can also be an R package (source, or binary), in which case the DESCRIPTION file is extracted from it, but note that in this case $write() cannot write the file back in the package archive.

text:

A character scalar containing the full DESCRIPTION. Character vectors are collapsed into a character scalar, with newline as the separator.

package

If not NULL, then the name of an installed package and the DESCRIPTION file of this package will be loaded.

Setting and Querying fields

Set a field with $set and query it with $get:

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  x <- description$new("!new")
  x$get("Package)
  x$set("Package", "foobar")
  x$set(Title = "Example Package for 'description'")
  x$get("Package")

Note that $set has two forms. You can either give the field name and new value as two arguments; or you can use a single named argument, the argument name is the field name, the argument value is the field value.

The $fields method simply lists the fields in the object:

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  x$fields()

The $has_fields method checks if one or multiple fields are present in a description object:

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  x$has_fields("Package")
  x$has_fields(c("Title", "foobar"))

The $del method removes the specified fields:

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  x$set(foo = "bar")
  x$del("foo")

$get_field is similar to $get, but it queries a single field, it returns an unnamed vector if found, and returns the specified default value if not. By default it throws an error if the field is not found.

The complete API reference:

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  description$get(keys)
  description$get_field(key, default, trim_ws = TRUE)
  description$set(...)
  description$fields()
  description$has_fields(keys)
  description$del(keys)
key:

A character string (length one), the key to query.

default:

If specified and key is missing, this value is returned. If not specified, an error is thrown.

trim_ws:

Whether to trim leading and trailing whitespace from the returned value.

keys:

A character vector of keys to query, check or delete.

...:

This must be either two unnamed arguments, the key and and the value to set; or an arbitrary number of named arguments, names are used as keys, values as values to set.

Normalizing

Format DESCRIPTION in a standard way. $str formats each field in a standard way and returns them (it does not change the object itself), $print is used to print it to the screen. The $normalize function normalizes each field (i.e. it changes the object). Normalization means reformatting the fields, via $reformat_fields() and also reordering them via $reorder_fields(). The format of the various fields is opinionated and you might like it or not. Note that desc only re-formats fields that it updates, and only on demand, so if your formatting preferences differ, you can still manually edit DESCRIPTION and desc will respect your edits.

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  description$str(by_field = FALSE, normalize = TRUE,
    mode = c("file", "screen"))
  description$normalize()
  description$reformat_fields()
  description$reorder_fields()
  description$print()
by_field:

Whether to return the normalized format by field, or collapsed into a character scalar.

normalize:

Whether to reorder and reformat the fields.

mode:

‘file’ mode formats the fields as they are written to a file with the write method. ‘screen’ mode adds extra markup to some fields, e.g. formats the Authors@R field in a readable way.

Writing it to file

The $write method writes the description to a file. By default it writes it to the file it was created from, if it was created from a file. Otherwise giving a file name is compulsory:

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  x$write(file = "DESCRIPTION")

The normalize argument controls whether the fields are reformatted according to a standard style. By default they are not.

The API:

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  description$write(file = NULL, normalize = NULL)
file:

Path to write the description to. If it was created from a file in the first place, then it is written to the same file. Otherwise this argument must be specified.

normalize:

Whether to reformat the fields in a standard way.

Version numbers

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  description$get_version()
  description$set_version(version)
  description$bump_version(which = c("patch", "minor", "major", "dev"))
version:

A string or a package_version object.

which:

Which component of the version number to increase. See details just below.

These functions are simple helpers to make it easier to query, set and increase the version number of a package.

$get_version() returns the version number as a package_version object. It throws an error if the package does not have a ‘Version’ field.

$set_version() takes a string or a package_version object and sets the ‘Version’ field to it.

$bump_version() increases the version number. The which parameter specifies which component to increase. It can be a string referring to a component: ‘major’, ‘minor’, ‘patch’ or ‘dev’, or an integer scalar, for the latter components are counted from one, and the beginning. I.e. component one is equivalent to ‘major’.

If a component is bumped, then the ones after it are zeroed out. Trailing zero components are omitted from the new version number, but if the old version number had at least two or three components, then the one will also have two or three.

The bumping of the ‘dev’ version (the fourth component) is special: if the original version number had less than four components, and the ‘dev’ version is bumped, then it is set to 9000 instead of 1. This is a convention often used by R developers, it was originally invented by Winston Chang.

Both $set_version() and $bump_version() use dots to separate the version number components.

Dependencies

These functions handle the fields that define how the R package uses another R packages. See dep_types for the list of fields in this group.

The $get_deps method returns all declared dependencies, in a data frame with columns: type, package and version. type is the name of the dependency field, package is the name of the R package, and version is the required version. If no specific versions are required, then this is a "\*".

The $set_deps method is the opposite of $get_deps and it sets all dependencies. The input is a data frame, with the same structure as the return value of $get_deps.

The $has_dep method checks if a package is included in the dependencies. It returns a logical scalar. If type is not ‘any’, then it has to match as well.

The $del_deps method removes all declared dependencies.

The $set_dep method adds or updates a single dependency. By default it adds the package to the Imports field.

The API:

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  description$set_dep(package, type = dep_types, version = "\*")
  description$set_deps(deps)
  description$get_deps()
  description$has_dep(package, type = c("any", dep_types))
  description$del_dep(package, type = c("all", dep_types))
  description$del_deps()
package:

Name of the package to add to or remove from the dependencies.

type:

Dependency type, see dep_types. For $del_dep it may also be "all", and then the package will be deleted from all dependency types.

version:

Required version. Defaults to "\*", which means no explicit version requirements.

deps:

A data frame with columns type, package and version. $get_deps returns the same format.

Collate fields

Collate fields contain lists of file names with R source code, and the package has a separate API for them. In brief, you can use $add_to_collate to add one or more files to the main or other collate field. You can use $del_from_collate to remove it from there.

The API:

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  description$set_collate(files, which = c("main", "windows", "unix"))
  description$get_collate(which = c("main", "windows", "unix"))
  description$del_collate(which = c("all", "main", "windows", "unix"))
  description$add_to_collate(files, which = c("default", "all", "main",
    "windows", "unix"))
  description$del_from_collate(files, which = c("all", "main",
    "windows", "unix"))
files:

The files to add or remove, in a character vector.

which:

Which collate field to manipulate. "default" for $add_to_collate means all existing collate fields, or the main one if none exist.

Authors

There is a specialized API for the Authors@R field, to add and remove authors, update their roles, change the maintainer, etc.

The API:

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  description$get_authors()
  description$set_authors(authors)
  description$get_author(role)
  description$get_maintainer()
  description$coerce_authors_at_r()
authors:

A person object, a list of authors.

role:

The role to query. See person for details.

$get_authors returns a person object, the parsed authors. See person for details.

$get_author returns a person object, all authors with the specified role.

$get_maintainer returns the maintainer of the package. It works with Authors@R fields and with traditional Maintainer fields as well.

$coerce_authors_at_r converts an Author field to one with a person object. This coercion may be necessary for other functions such as $get_authors.

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  description$add_author(given = NULL, family = NULL, email = NULL,
    role = NULL, comment = NULL, orcid = NULL)
  description$add_me(role = "ctb", comment = NULL, orcid = NULL)
  description$add_author_gh(username, role = "ctb", comment = NULL, orcid = NULL)

Add a new author. The arguments correspond to the arguments of the person function. add_me is a convenience function, it adds the current user as an author, and it needs the whoami package to be installed. It'll add your ORCID ID if you provide it as argument or save it as ORCID_ID environment variable in .Renviron. The full name is parsed by add_me and add_author_gh using as.person and collapsing the given name and the family name in order to e.g. have the first and middle names together as given name. This approach might be limited to some full name structures.

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  description$del_author(given = NULL, family = NULL, email = NULL,
    role = NULL, comment = NULL, orcid = NULL)

Remove an author, or multiple authors. The author(s) to be removed can be specified via any field(s). All authors matching all specifications will be removed. E.g. if only given = "Joe" is supplied, then all authors whole given name matches Joe will be removed. The specifications can be (PCRE) regular expressions.

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  description$add_role(role, given = NULL, family = NULL, email = NULL,
    comment = NULL, orcid = NULL)
    description$add_orcid(orcid, given = NULL, family = NULL, email = NULL,
    comment = NULL, role = NULL)
  description$del_role(role, given = NULL, family = NULL, email = NULL,
     comment = NULL, orcid = NULL)
  description$change_maintainer(given = NULL, family = NULL,
    email = NULL, comment = NULL, orcid = NULL)

role is the role to add or delete. The other arguments are used to select a subset of the authors, on which the operation is performed, similarly to $del_author.

URLs

We provide helper functions for manipulating URLs in the URL field:

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  description$get_urls()
  description$set_urls(urls)
  description$add_urls(urls)
  description$del_urls(pattern)
  description$clear_urls()
urls:

Character vector of URLs to set or add.

pattern:

Perl compatible regular expression to specify the URLs to be removed.

$get_urls() returns all urls in a character vector. If no URL fields are present, a zero length vector is returned.

$set_urls() sets the URL field to the URLs specified in the character vector argument.

$add_urls() appends the specified URLs to the URL field. It creates the field if it does not exists. Duplicate URLs are removed.

$del_urls() deletes the URLs that match the specified pattern.

$clear_urls() deletes all URLs.

Remotes

devtools, remotes and some other packages support the non-standard Remotes field in DESCRIPTION. This field can be used to specify locations of dependent packages: GitHub or BitBucket repositories, generic git repositories, etc. Please see the ‘Package remotes’ vignette in the devtools package.

desc has helper functions for manipulating the Remotes field:

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  description$get_remotes()
  description$get_remotes()
  description$set_remotes(remotes)
  description$add_remotes(remotes)
  description$del_remotes(pattern)
  description$clear_remotes()
remotes:

Character vector of remote dependency locations to set or add.

pattern:

Perl compatible regular expression to specify the remote dependency locations to remove.

$get_remotes() returns all remotes in a character vector. If no URL fields are present, a zero length vector is returned.

$set_remotes() sets the URL field to the Remotes specified in the character vector argument.

$add_remotes() appends the specified remotes to the Remotes field. It creates the field if it does not exists. Duplicate remotes are removed.

$del_remotes() deletes the remotes that match the specified pattern.

$clear_remotes() deletes all remotes.

Built

The ‘Built’ field is used in binary packages to store information about when and how a binary package was built.

$get_built() returns the built information as a list with fields ‘R’, ‘Platform’, ‘Date’, ‘OStype’. It throws an error if the package does not have a ‘Built’ field.

Encodings

When creating a 'description' object, 'desc' observes the 'Encoding' field, if present, and uses the specified encoding to parse the file. Internally, it converts all fields to UTF-8.

When writing a 'description' object to a file, 'desc' uses the 'Encoding' field (if present), and converts all fields to the specified encoding.

We suggest that whenever you need to use non-ASCII characters in your package, you use the UTF-8 encoding, for maximum portability.

Examples

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## Create a template
desc <- description$new("!new")
desc

## Read a file
desc2 <- description$new(file = system.file("DESCRIPTION",
                           package = "desc"))
desc2

## Remove a field
desc2$del("LazyData")

## Add another one
desc2$set(VignetteBuilder = "knitr")
desc2$get("VignetteBuilder")
desc2

desc documentation built on March 6, 2021, 1:06 a.m.