doomemacs/modules/tools/lookup/README.org

#+TITLE:   tools/lookup
#+DATE:    January 4, 2018
#+SINCE:   v2.0.9
#+STARTUP: inlineimages

* Table of Contents :TOC:
- [[#description][Description]]
  - [[#module-flags][Module Flags]]
  - [[#plugins][Plugins]]
- [[#prerequisites][Prerequisites]]
  - [[#macos][MacOS]]
  - [[#arch-linux][Arch Linux]]
- [[#features][Features]]
  - [[#jump-to-definition][Jump to definition]]
  - [[#find-references][Find references]]
  - [[#look-up-documentation][Look up documentation]]
  - [[#search-a-specific-documentation-backend][Search a specific documentation backend]]
  - [[#dashapp-docset-integration][Dash.app Docset integration]]
- [[#configuration][Configuration]]
  - [[#associating-lookup-handlers-with-major-modes][Associating lookup handlers with major modes]]
  - [[#associating-dash-docsets-with-major-modes][Associating Dash docsets with major modes]]
  - [[#open-in-eww-instead-of-browser][Open in eww instead of browser]]
- [[#appendix][Appendix]]
  - [[#commands][Commands]]

* Description
Integrates with code navigation and documentation tools to help you quickly look
up definitions, references and documentation.

+ Jump-to-definition and find-references implementations that just work.
+ Powerful xref integration for languages that support it.
+ Documentation lookup for a variety of online sources (like devdocs.io,
  stackoverflow or youtube).
+ Integration with Dash.app docsets.

** Module Flags
+ ~+docsets~ Enable integration with Dash.app docsets.

** Plugins
+ [[https://github.com/jacktasia/dumb-jump][dumb-jump]]
+ [[https://github.com/alexmurray/ivy-xref][ivy-xref]] or [[https://github.com/brotzeit/helm-xref][helm-xref]]
+ [[https://github.com/nathankot/counsel-dash][counsel-dash]] or [[https://github.com/areina/helm-dash][helm-dash]]

* Prerequisites
This module has several soft dependencies:

+ ~the_silver_searcher~ or ~ripgrep~ (recommended) as a last-resort fallback for
  jump-to-definition/find-references.
+ ~sqlite3~ for Dash docset support.

** MacOS
#+BEGIN_SRC sh
brew install the_silver_searcher ripgrep

# 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"
#+END_SRC

** Arch Linux
#+BEGIN_SRC sh
sudo pacman -S sqlite the_silver_searcher ripgrep
#+END_SRC

* Features
** 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).
3. An ordinary project-wide text search with ripgrep or the_silver_searcher.
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.

** 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 or the_silver_searcher.

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

** 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).

** 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.

** Dash.app Docset integration
You can install dash docsets with ~M-x +lookup/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.

* Configuration
** Associating lookup handlers with major modes
~set-lookup-handlers! MODES &key DEFINITION REFERENCES DOCUMENTATION FILE XREF-BACKEND ASYNC~

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.

e.g.
#+BEGIN_SRC emacs-lisp
;; 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.
#+END_SRC

** 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~.

e.g.
#+BEGIN_SRC emacs-lisp
(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")
#+END_SRC

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 ~+lookup/install-docset~.

** Open in eww instead of browser
To open results from ~+lookup/online~ in EWW instead of your system browser,
change ~+lookup-open-url-fn~ (default: ~#'browse-url~):

#+BEGIN_SRC emacs-lisp
(setq +lookup-open-url-fn #'eww)
#+END_SRC

* Appendix
** Commands
+ ~+lookup/definition~
+ ~+lookup/references~
+ ~+lookup/documentation~
+ ~+lookup/online~
+ ~+lookup/online-select~
+ ~+lookup/in-devdocs~
+ ~+lookup/in-docsets~