#+TITLE: Tern layer

[[file:img/tern.png]]

* Table of Contents                     :TOC_4_gh:noexport:
- [[#description][Description]]
  - [[#features][Features:]]
- [[#install][Install]]
- [[#configuration][Configuration]]
  - [[#custom-tern-command][Custom tern command]]
  - [[#re-use-the-server-across-multiple-different-editing-sessions][Re-use the server across multiple different editing sessions]]
- [[#key-bindings][Key bindings]]

* Description
This layer adds support for [[http://ternjs.net/][tern]] stand-alone code-analysis engine for
JavaScript.

** Features:
- TODO: list the feature of tern supported by tern package

* Install
To use this configuration layer, add it to your =~/.spacemacs=. You will need to
add =tern= to the existing =dotspacemacs-configuration-layers= list in this
file.

You can install =tern= globally with the following command:

#+BEGIN_SRC sh
  $ npm install -g tern
#+END_SRC

* Configuration
** Custom tern command
Windows users may need to set the variable =tern-command= in order for emacs to
locate and launch tern server successfully. See [[https://github.com/syl20bnr/spacemacs/issues/5733][this open issue for more
details]]. The variable can be set by adding the =tern= layer with this
configuration layer:

#+BEGIN_SRC emacs-lisp
  (tern :variables tern-command '("node" "/path/to/tern/bin/tern"))
#+END_SRC

Note: =tern-command= must be a list of strings.

** Re-use the server across multiple different editing sessions
By default =tern= is setup to not create multiple =.tern-port= files in your
repository.

To make tern re-use the server across multiple different editing sessions (thus
creating multiple =.tern-port= files for each document you have open [[http://ternjs.net/doc/manual.html][see here
for more details]]) set the variable =tern-disable-port-files= to nil:

#+BEGIN_SRC emacs-lisp
  (tern :variables tern-disable-port-files nil)
#+END_SRC

* Key bindings

| Key binding   | Description                                                                              |
|---------------+------------------------------------------------------------------------------------------|
| ~SPC m C-g~   | brings you back to last place you were when you pressed M-..                             |
| ~SPC m g g~   | jump to the definition of the thing under the cursor                                     |
| ~SPC m g G~   | jump to definition for the given name                                                    |
| ~SPC m h d~   | find docs of the thing under the cursor. Press again to open the associated URL (if any) |
| ~SPC m h t~   | find the type of the thing under the cursor                                              |
| ~SPC m r r V~ | rename variable under the cursor using tern                                              |