elisp-def

Go to the definition of the symbol at point. Supports global definitions, local definitions, and even macro-heavy code!

elisp-def statically analyses your code, and falls back to heuristics where that's not possible. It should work 99% of the time, so please file bugs if it can't find definitions for your code.

Installation

Install from MELPA, then add the following to your Emacs configuration:

(dolist (hook '(emacs-lisp-mode-hook ielm-mode-hook))
  (add-hook hook #'elisp-def-mode))

Global Definitions

elisp-def will find the definition of global functions and global variables at point.

(defun demo/foo ()
  1)

(defun demo/bar ()
  ;; M-x eval-buffer, then elisp-def on this:
  (demo/foo))

It will also use edebug information to find function definitions, so it finds definitions more often than xref.

Lisp-2 Awareness

elisp-def understands the difference between symbols and functions and jumps to the correct definition.

(require 'cc-mode)

;; `c-version' is both a variable and a function.

(defun demo/foo ()
  ;; `elisp-def` will find the function here.
  (c-version))

(defun demo/foo ()
  ;; `elisp-def` will find the variable here.
  (setq c-version t))

Macro Awareness

elisp-def understands macros, so it can accurately detect function references.

(require 'dash)

(defvar demo/foo nil)

(defun demo/foo (x)
  x)

(defun demo/bar ()
  (->> 123
       ;; `elisp-def' knows that this is a function, even though there are
       ;; no parens.
       demo/foo))

It can also understand macros that define functions or variables.

(define-derived-mode demo/foo-mode fundamental-mode "demo")

;; `elisp-def' will expand macros to discover where major mode hooks
;; are defined.
demo/foo-mode-hook

(cl-defstruct demo/point x y)

;; `elisp-def' can find this function even though the defstruct
;; call doesn't contain this symbol name.
(make-demo/point 1 2)

Find Libraries

elisp-def will find libraries, displaying the provide declarations if possible.

;; `elisp-def' will open python.el here.
(require 'python)

;; Unlike `xref-find-definition', `elisp-def' will not confuse this
;; library name with the macro named `use-package'.
(require 'use-package)

;; `elisp-def' will even find python.el here, because the macro
;; expands to a call to `require'.
(use-package python
  :config
  (setq python-indent-guess-indent-offset-verbose nil))

Local Bindings

elisp-def understands local bindings and parameters.

(defun demo/foo (bar)
  (let ((foo 1))
    ;; `elisp-def' on the FOO below will move point to the let
    ;; binding.
    (setq foo 2)
    ;; `elisp-def' on the BAR below will move point to the function
    ;; parameters line.
    (setq bar 3)))

(defun demo/bar ()
  (let* ((foo 1)
         (bar 2)
         (foo 3)
         ;; `elisp-def' on the second FOO on the following line will
         ;; move point to the relevant binding, which is the line
         ;; immediately above.
         (foo (+ foo 1))
         (foo 5))
    nil))

This even works with macros that introduce bindings.

(require 'dash)
(eval-when-compile
  (require 'cl-lib))

(defun demo/foo (items)
  (cl-destructuring-bind (first second) items
    ;; `elisp-def' knowns that FIRST is bound on line above.
    (message "first is %s" first))
  (-let [(first . rest) items]
    ;; `elisp-def' knowns that FIRST is bound on line above.
    (message "first is %s" first)))

Ergonomics

elisp-def allows you to put point on quoted symbols, docstring symbols or backquoted symbols.

(defun demo/foo (x)
  ;; `elisp-def' on X in the docstring will find the parameter.
  "Adds one to X and returns it."
  (1+ x))

(defun demo/bar ()
  ;; `elisp-def' can find demo/foo even when point is on the #.
  (funcall #'demo/foo 1)
  ;; `elisp-def' on demo/foo below will find the function.
  ;;
  ;; See `demo/foo' for more information.
  nil)

(defun demo/baz (foo)
  ;; `elisp-def' understands that @ is not part of foo here.
  `(blah ,@foo))

When it finds the symbol, elisp-def will also temporarily highlight it for visibility.

Caveats

elisp-def is limited in its ability to analyse quoted symbols.

;; `elisp-def' is able to find these quoted symbols because they're
;; only globally bound in one namespace.
(mapcar 'symbol-name '(foo bar baz))
(add-to-list 'auto-mode-alist '("\\.java\\'" . java-mode))

(require 'cc-mode)
(defun demo/calls-fn (sym)
  (funcall sym))

;; Since `c-version' is both a function and a variable, and we're not
;; using a sharp-quote #'c-version, we have to prompt the user.
(demo/calls-fn 'c-version)

(defun demo/foo (c-version)
  ;; Here we have no idea whether we're using `c-version' as a
  ;; function (e.g. funcall), as a variable (e.g. set) or as a
  ;; parameter (e.g. eval).
  (bar 'c-version nil))

elisp-def cannot find definitions in macros with let* semantics and duplicated variables.

(require 'dash)

(defun demo/foo ()
  (-let ((x 1)
         (x 2))
    ;; `elisp-def' on X below will move to the first X binding, rather
    ;; than the second.
    x))

elisp-def also cannot handle macros that rewrite forms such that the symbol disappears entirely.

(eval-when-compile (require 'cl-lib))

(cl-labels ((foo (x y) (+ x y)))
  ;; `cl-labels' completely rewrites this body to (--cl-foo-- 1 2), so
  ;; `elisp-def' can't find the definition of FOO.
  (foo 1 2))

Thanks/Inspirations

elisp-slime-nav-find-elisp-thing-at-point from elisp-slime-nav
xref-find-definitions in emacs-lisp-mode (part of Emacs core)
semantic-ia-fast-jump from semantic/ia.el (included in Emacs)

The fine folks on #emacs for answering my questions on elisp esoterica, particularly Wasamasa.

The compliment library for Clojure completion has a notion of context which is very similar to how elisp-def extracts and analyses forms.

Hacklang has a similar notion of a placeholder for analysing completions at a point in the code.

License

GPLv3+.

I am providing code in the repository to you under an open source license. Because this is my personal repository, the license you receive to my code is from me and not my employer.

slamko/elisp-def