Package {rdtools}

Title:	Efficient Manipulation of 'Rd' Files and Help Topics
Version:	0.1.0
Description:	Provides fast, cached lookup of help topics and aliases across installed, source, and in-development packages, plus efficient retrieval of parsed 'Rd' ('R' documentation) objects. Per-package indexes are built once and cached, making repeated retrieval cheap enough to call in a tight loop.
License:	MIT + file LICENSE
URL:	https://rdtools.r-lib.org, https://github.com/r-lib/rdtools
BugReports:	https://github.com/r-lib/rdtools/issues
Depends:	R (≥ 4.0)
Imports:	stats, tools
Suggests:	testthat (≥ 3.0.0), withr
Config/testthat/edition:	3
Encoding:	UTF-8
RoxygenNote:	8.0.0
Config/Needs/website:	tidyverse/tidytemplate
NeedsCompilation:	yes
Packaged:	2026-07-07 19:24:27 UTC; hadleywickham
Author:	Hadley Wickham [aut, cre, cph], Posit Software, PBC [cph, fnd]
Maintainer:	Hadley Wickham <hadley@posit.co>
Repository:	CRAN
Date/Publication:	2026-07-16 13:20:02 UTC

rdtools: Efficient Manipulation of 'Rd' Files and Help Topics

Description

Provides fast, cached lookup of help topics and aliases across installed, source, and in-development packages, plus efficient retrieval of parsed 'Rd' ('R' documentation) objects. Per-package indexes are built once and cached, making repeated lookups cheap enough to call in a tight loop.

Author(s)

Maintainer: Hadley Wickham hadley@posit.co (ORCID) [copyright holder]

Authors:

• Hadley Wickham hadley@posit.co (ORCID) [copyright holder]

Other contributors:

• Posit Software, PBC (ROR) [copyright holder, funder]

See Also

Useful links:

• https://github.com/r-lib/rdtools

• Report bugs at https://github.com/r-lib/rdtools/issues

Reset cached package indexes

Description

Clears the cached topic index, parsed Rd objects, and dependency search set for package, or for every package when package is NULL. This will generally be called automatically by roxygen2 for source packages. Installed package indexes are automatically reset when their namespace is unloaded.

Usage

pkg_cache_reset(package = NULL)

Arguments

Value

NULL, invisibly.

Examples

head(pkg_topics("stats"))
pkg_cache_reset("stats")

# Reset every cached index
pkg_cache_reset()

Load a package's Rd macros

Description

Loads the macros declared by the package's RdMacros field and ⁠man/macros/⁠ directory, layered over R's system macros. This reproduces the macro environment used when installing a package.

Usage

pkg_macros(package)

Arguments

Value

An environment containing the Rd macro definitions.

Examples

macros <- pkg_macros("stats")
head(ls(macros))

Packages searched for help by default

Description

pkg_search_attached() returns the packages a bare ?topic can see: every attached package, in search path order, followed by the base packages that are always available. This is the default search set for topic_find().

pkg_search_base() returns the base packages that are always searched.

Usage

pkg_search_attached()

pkg_search_base()

Value

A character vector of package names.

Examples

pkg_search_attached()
pkg_search_base()

Packages to search for topics in a package's dependencies

Description

pkg_search_deps() returns the packages whose topics package's documentation can link to: the packages declared in its Depends, Imports, and Suggests fields, followed by the base packages, which are always available. The result is cached alongside the package's topic index, so it remains valid until pkg_cache_reset() is called.

Usage

pkg_search_deps(package)

Arguments

Value

A character vector of package names.

Examples

pkg_search_deps("stats")

List the topics documented by a package

Description

pkg_topics() returns a named character vector mapping every alias (i.e. everything you can type after ⁠?⁠) to the name of the Rd file (without extension) that documents it. It understands three kinds of package:

• Installed packages, read from their help/aliases.rds index.

• In-development packages loaded with pkgload::load_all(), indexed from the ⁠\alias{}⁠ commands in their source ⁠man/⁠ directory.

• Source packages, when package is a path to a package directory rather than a name.

Indexes remain cached until pkg_cache_reset() is called. Installed package indexes are also reset automatically when their namespace is unloaded.

For source packages, ⁠\alias{}⁠ extraction is line-based: any number of aliases may appear anywhere on a line, but an alias must open and close on the same line, and aliases produced by Rd macros are not seen.

Usage

pkg_topics(package)

Arguments

Value

A named character vector mapping alias to Rd file name.

Examples

head(pkg_topics("stats"))

Is a topic documented?

Description

Checks whether any of packages has an exact alias matching topic.

Usage

topic_exists(topic, packages = pkg_search_attached())

Arguments

Value

A single TRUE or FALSE.

Examples

topic_exists("rnorm", "stats")
topic_exists("rnorm", c("base", "stats"))
topic_exists("median")
topic_exists("not-a-topic", "stats")

Find packages that document a topic

Description

topic_find() looks topic up in each of packages in order and returns the first hit. topic_find_all() returns every hit. Lookups use the cached per-package indexes built by pkg_topics(), so scanning even a long search set is cheap.

Usage

topic_find(topic, packages = pkg_search_attached())

topic_find_all(topic, packages = pkg_search_attached())

Arguments

Value

topic_find() returns NULL if the topic isn't found; otherwise a list with elements:

• package: the package that documents the topic.

• file: the name of the Rd file (without extension).

topic_find_all() returns a data frame with columns package and file, containing one row per hit (and no rows if the topic isn't found).

Examples

topic_find("rnorm")
topic_find("mean", c("stats", "base"))
topic_find_all("plot", c("graphics", "base"))
topic_find("no-such-topic")

Find the package where a topic's object originates

Description

Determines which package supplies the object associated with a documented topic. This resolves re-exported functions and imported objects to the package where they originate. Results are cached alongside the package's topic index, so repeated lookups are cheap.

Usage

topic_origin(topic, package)

Arguments

Value

A single package name.

Examples

topic_origin("rnorm", "stats")

Find the package qualifier for a topic

Description

Determines whether a topic needs a package qualifier when linking from the documentation of another package. The from package is checked first, followed by packages, and then the base packages. Re-exported objects are attributed to their original package. Results are cached alongside the from package's topic index, so repeated lookups are cheap.

Usage

topic_qualifier(topic, from, packages = character())

Arguments

Value

• NULL if the topic isn't documented by from, packages, or the base packages.

• NA_character_ if the topic needs no qualifier because it's documented by from or a base package.

• Otherwise, the package name(s) that could qualify the topic: usually one, but more if the topic is ambiguous, in which case it's up to the caller to decide how to respond.

Examples

topic_qualifier("rnorm", "stats")

Get the parsed Rd for a topic

Description

Retrieves the parsed Rd object documenting topic in package. For installed packages the topic is fetched lazily from the package's help database (no parsing needed); for source and in-development packages the Rd file is parsed with tools::parse_Rd(), with the package's Rd macros loaded. Results are cached per topic, so repeated access (e.g. roxygen2 inheriting several fields from one topic) only pays once.

Usage

topic_rd(topic, package)

Arguments

Value

An Rd object: a recursive structure of class "Rd", as returned by tools::parse_Rd(). Returns NULL if the package or topic doesn't exist; use topic_exists() first if you need to distinguish that from other problems.

Examples

rd <- topic_rd("rnorm", "stats")
class(rd)

Get the path to the Rd file for a topic

Description

Returns the path to the .Rd file that documents topic. Rd files only exist on disk for source and in-development packages; installed packages store their documentation in a binary database, so topic_rd_path() returns NULL for them. Use topic_rd() if you want the parsed contents regardless of where they are stored.

Usage

topic_rd_path(topic, package)

Arguments

Value

The path to a .Rd file, or NULL if the package or topic doesn't exist, or if the package doesn't have Rd files on disk.

Examples

# Rd files only exist on disk for source packages, so make a minimal one
pkg <- tempfile()
dir.create(file.path(pkg, "man"), recursive = TRUE)
writeLines("Package: demo", file.path(pkg, "DESCRIPTION"))
writeLines(
  c("\\name{foo}", "\\alias{foo}", "\\title{Foo}", "\\description{Foo.}"),
  file.path(pkg, "man", "foo.Rd")
)

topic_rd_path("foo", pkg)

Split a qualified topic into package and topic

Description

Splits "pkg::topic" (or "pkg:::topic") into its package and topic components. The prefix is only treated as a qualifier when it is a syntactically valid package name, so aliases that merely contain :: (e.g. S7 method aliases like "speak,foo::Dog-method") are left intact.

Usage

topic_split(topic)

Arguments

Value

A list with elements package (a string, or NULL if the topic is unqualified) and topic.

Examples

topic_split("stats::rnorm")
topic_split("rnorm")
topic_split("speak,foo::Dog-method")