:tools lookup

navigate your code and its documentation

1. Description

This module adds code navigation and documentation lookup tools to help you quickly look up definitions, references, documentation, dictionary definitions or synonyms.

  • Jump-to-definition and find-references implementations that just work.
  • Powerful xref integration for languages that support it.
  • Search online providers like devdocs.io, stackoverflow, google, duckduckgo or youtube (duckduckgo and google have live suggestions).
  • Integration with Dash.app docsets.
  • Support for online (and offline) dictionaries and thesauruses.

1.1. Module flags

Enable word definition and thesaurus lookup functionality.
Enable integration with Dash.app docsets.
Prefer offline dictionary and thesaurus. Requires +dictionary.

2. Prerequisites

This module has several soft dependencies:

  • ripgrep as a last-resort fallback for jump-to-definition/find-references.
  • sqlite3 for Dash docset support (if you have +docsets enabled)
  • wordnet for offline dictionary and thesaurus support (if you have +dictionary +offline enabled).

2.1. MacOS

$ brew install ripgrep wordnet

# An older version of sqlite is included in MacOS. If it causes you problems (and
# folks have reported it will), install it through homebrew:
$ brew install sqlite
# Note that it's keg-only, meaning it isn't symlinked to /usr/local/bin. You'll
# have to add it to PATH yourself (or symlink it into your PATH somewhere). e.g.
$ export PATH="/usr/local/opt/sqlite/bin:$PATH"

2.2. Arch Linux

$ sudo pacman -S sqlite ripgrep
$ yay -S wordnet-cli

2.3. NixOS

environment.systemPackages = with pkgs; [

3. Usage

3.1. Jump to definition

Use +lookup/definition (bound to gd in normal mode) to jump to the definition of the symbol at point

This module provides a goto-definition implementation that will try the following sources before giving up:

  1. Whatever :definition function is registered for the current buffer with the :lookup setting (see “Configuration” section).
  2. Any available xref backends.
  3. dumb-jump (a text search with aides to reduce false positives).
  4. An ordinary project-wide text search with ripgrep.
  5. If evil-mode is active, use evil-goto-definition, which preforms a simple text search within the current buffer.

If there are multiple results, you will be prompted to select one.

3.2. Find references

Use +lookup/references (bound to gD in normal mode) to see a list of references for the symbol at point from throughout your project.

Like +lookup/definition, this tries a number of sources before giving up. It will try:

  1. Whatever :references function is registered for the current buffer with the :lookup setting (see “Configuration” section).
  2. Any available xref backends.
  3. An ordinary project-wide text search with ripgrep.

If there are multiple results, you will be prompted to select one.

3.3. Look up documentation

+lookup/documentation (bound to K in normal mode) will open documentation for the symbol at point.

Depending on your configuration, this will try a list of sources:

  1. Whatever :documentation function is registered for the current buffer with the :lookup setting (see “Configuration” section).
  2. Any Dash.app docsets, if any are installed for the current major mode.
  3. devdocs.io, if it has a docset for the current mode.
  4. An online search; using the last engine used (it will prompt you the first time, or if current-prefix-arg is non-nil).

3.4. Search a specific documentation backend

You can perform a documentation lookup on any backends directly:

  • Dash Docsets: +lookup/in-docsets, or :dash QUERY for evil users.
  • Online (generic): +lookup/online or +lookup/online-select (bound to SPC / o), or :lo[okup] QUERY for evil users.

3.5. Dash.app Docset integration

You can install dash docsets with M-x dash-docset-install-docset and search them offline with M-x +lookup/in-docsets, or with +lookup/documentation in modes that don’t have a specialized :documentation lookup handler.

4. Configuration

4.1. Associating lookup handlers with major modes


Use set-lookup-handlers! to register lookup targets for MODES (a major or minor mode symbol or list thereof). PLIST accepts the following optional properties:

:definition FN
Run when jumping to a symbol’s definition. Used by +lookup/definition.
:references FN
Run when looking for usage references of a symbol in the current project. Used by +lookup/references.
:documentation FN
Run when looking up documentation for a symbol. Used by +lookup/documentation.
:file FN
Run when looking up the file for a symbol/string. Typically a file path. Used by +lookup/file.
:xref-backend FN
Defines an xref backend, which implicitly provides :definition and :references handlers. If you specify them anyway, they will take precedence over the xref backend, however.


;; For python-mode, anaconda-mode offers a backend for all three lookup
;; functions. We can register them like so:
(set-lookup-handlers! 'python-mode
  :definition #'anaconda-mode-find-definitions
  :references #'anaconda-mode-find-references
  :documentation #'anaconda-mode-show-doc)

;; If a language or plugin provides a custom xref backend available for it, use
;; that instead. It will provide the best jump-to-definition and find-references
;; experience. You can specify custom xref backends with:
(set-lookup-handlers! 'js2-mode :xref-backend #'xref-js2-xref-backend)
;; NOTE: xref doesn't provide a :documentation backend.

4.2. Associating Dash docsets with major modes

set-docsets! MODES &rest DOCSETS...

Use set-docsets! to register DOCSETS (one string or list of strings) for MODES (one major mode symbol or a list of them). It is used by +lookup/in-docsets and +lookup/documentation.


(set-docsets! 'js2-mode "JavaScript" "JQuery")
;; Add docsets to minor modes by starting DOCSETS with :add
(set-docsets! 'rjsx-mode :add "React")
;; Or remove docsets from minor modes
(set-docsets! 'nodejs-mode :remove "JQuery")

This determines what docsets to implicitly search for when you use +lookup/documentation in a mode with no :documentation handler. Those docsets must be installed with dash-docset-install-docset.

4.3. Open in eww instead of browser

+lookup/online opens the search results with in +lookup-open-url-fn (default: #'browse-url). Here is how to change this to EWW (so it opens inside Emacs):

(setq +lookup-open-url-fn #'eww)

+lookup/in-docsets consults dash-docs-browser-func instead, which is already set to #'eww by default.

4.4. Open in Xwidget WebKit instead of browser

To open results from +lookup/online or +lookup/in-docsets in Xwidget WebKit instead of your system browser, set +lookup-open-url-fn and/or dash-docs-browser-func to +lookup-xwidget-webkit-open-url-fn (needs Emacs with Xwidgets support):

(setq +lookup-open-url-fn #'+lookup-xwidget-webkit-open-url-fn)
(after! dash-docs
  (setq dash-docs-browser-func #'+lookup-xwidget-webkit-open-url-fn))

5. Troubleshooting

There are no known problems with this module. Report one?

6. Appendix

6.1. Commands

  • +lookup/definition
  • +lookup/references
  • +lookup/documentation
  • +lookup/online
  • +lookup/online-select
  • +lookup/in-devdocs
  • +lookup/in-docsets