#+TITLE: Spacemacs Conventions

* Table of Contents                     :TOC_5_gh:noexport:
- [[#code-guidelines][Code guidelines]]
  - [[#spacemacs-core-and-layer][Spacemacs core and layer]]
  - [[#all-layers][All layers]]
  - [[#use-package][Use-package]]
- [[#key-bindings-conventions][Key bindings conventions]]
  - [[#reserved-prefix][Reserved prefix]]
    - [[#user-prefix][User prefix]]
    - [[#major-mode-prefix][Major mode prefix]]
    - [[#transient-state][Transient-state]]
  - [[#special-mode-buffers][Special-mode buffers]]
  - [[#evilified-buffers][Evilified buffers]]
  - [[#navigation][Navigation]]
    - [[#n-and-n][n and N]]
    - [[#code-navigation][Code Navigation]]
    - [[#insert-state-buffers][=insert state= buffers]]
  - [[#confirm-and-abort][Confirm and Abort]]
  - [[#evaluation][Evaluation]]
  - [[#repls][REPLs]]
    - [[#send-code][Send code]]
    - [[#in-terminal][In terminal]]
  - [[#building-and-compilation][Building and Compilation]]
  - [[#debugging][Debugging]]
  - [[#errors][Errors]]
  - [[#plain-text-markup-languages][Plain Text Markup Languages]]
    - [[#headers][Headers]]
    - [[#insertion-of-common-elements][Insertion of common elements]]
    - [[#text-manipulation][Text manipulation]]
    - [[#movement-in-normal-mode][Movement in normal mode]]
    - [[#promotion-demotion-and-element-movement][Promotion, Demotion and element movement]]
    - [[#table-editing][Table editing]]
  - [[#tests][Tests]]
    - [[#all-languages][All languages]]
    - [[#language-specific][Language specific]]
  - [[#toggles][Toggles]]
  - [[#refactoring][Refactoring]]
  - [[#imports][Imports]]
  - [[#code-formatting][Code Formatting]]
  - [[#web-frameworks][Web frameworks]]
  - [[#help-or-documentation][Help or Documentation]]
- [[#writing-documentation][Writing documentation]]
  - [[#spacing-in-documentation][Spacing in documentation]]

* Code guidelines
** Spacemacs core and layer
Function names follow these conventions:
- =spacemacs/xxx= is an interactive function called =xxx=
- =spacemacs//xxx= is a private function called =xxx= (implementation details)
- =spacemacs|xxx= is a /macro/ called =xxx=

Variables follow these conventions:
- =spacemacs-xxx= is a variable
- =spacemacs--xxx= is a private variable (implementation details)

** All layers
A package is initialized in a function with name =<layer>/init-xxx= where:
- =<layer>= is the layer name
- =xxx= is the package name

** Use-package
- Always use =progn= when a code block requires multiple lines for =:init= or
  =:config= keywords.
- If there is only one line of code then try to keep =:init= or =:config=
  keywords on the same line.
- Don't nest multiple =use-package= calls unless you have a very good reason
  to do it.

* Key bindings conventions
** Reserved prefix
*** User prefix
~SPC o~ and ~SPC m o~ must not be used by any layer. They are reserved for the
user.

*** Major mode prefix
~SPC m~ is reserved for the current major mode. Three keys bindings are not an
issue (ie. ~SPC m h d~) since ~SPC m~ can be accessed via ~​,​~.

*** Transient-state
Transient states are generally put behind the dot key ~.~, for instance the
windows manipulation transient state in ~SPC w .~.

When it is not possible to use the ~.~ (like in =helm= buffers) transient states
should be enabled with ~M-SPC~ and ~s-M-SPC~. We need the latter bindings on
macOS since ~M-SPC~ is used by the OS for spotlight.

It is recommended to make sure that ~q~ allows to leave the transient-state.

** Special-mode buffers
Except for =eww-mode= and evilified buffers (see next section), all buffers with
major-modes derived from =special-mode= open in motion-state by default. To
exclude buffers of such major-modes from getting evilified, add a regexp to
=evil-buffer-regexps=.

** Evilified buffers
/Evilifying/ a buffer is to set the =evilified state= as the default
state for the major mode of the buffer.

The =evilified state= is derived from the =emacs state= and modify the
map to:
- add ~hjkl~ navigation
- add scrolling feature on ~C-f~, ~C-b~, ~C-d~ and ~C-u~
- ~G~ and ~gg~ to go to the end and beginning of the buffer
- add jump back-forward in history on ~C-o~ and ~C-i~ respectively
- add incremental search with ~/~, ~n~ and ~N~
- enabling =evil-ex= on ~:~
- add =visual state= and =visual line state= on ~v~ and ~V~
- add yank on ~y~ _in visual state only_
- activate evil-leader key on ~SPC~

Setting the =evilified state= to a mode is done by calling the macro
=evilified-state-evilify-map=.

/Evilification/ rebinds shadowed key bindings according to the following
rules:
- alphabetic key bindings: ~x~ -> ~X~ -> ~C-x~ -> ~C-X~
- ~SPC~ -> ~​'​~
- ~/~ -> ~\~
- ~:~ -> ~|~
- ~C-g~ cannot be shadowed

If a key binding cannot be remapped then it is ignored and a warning message
is displayed in =*Messages*=.

** Navigation
*** n and N
To be consistent with the Vim way, ~n~ and ~N~ are favored over Emacs ~n~ and
~p~.

Ideally a transient-state should be provided to smooth the navigation
experience. A transient-state allows to repeat key bindings without entering
each time the prefix commands. More info on transient-states in the
[[https://github.com/syl20bnr/spacemacs/blob/develop/doc/DOCUMENTATION.org#transient-states][documentation]].

*** Code Navigation
The prefix for going to something is ~SPC m g~.

| Key     | Description                                     |
|---------+-------------------------------------------------|
| ~m g a~ | go to alternate file (i.e. =.h <--> .cpp=)      |
| ~m g b~ | go back to previous location (before last jump) |
| ~m g g~ | go to things under point                        |
| ~m g G~ | go to things under point in other window        |
| ~m g i~ | go to imports                                   |
| ~m g t~ | go to corresponding test file if any            |
| ~m g u~ | go/find usage of thing under point              |

*** =insert state= buffers
Navigation in buffers like =Helm= and =ido= which are in =insert state=
should be performed with ~C-j~ and ~C-k~ bindings for vertical movements.

| Key   | Description |
|-------+-------------|
| ~C-j~ | go down     |
| ~C-k~ | go up       |

** Confirm and Abort
Confirming and aborting actions which are bound to ~C-c C-c~ and ~C-c C-k~
in raw Emacs are mirrored in Spacemacs to:

| Key                     | Description               |
|-------------------------+---------------------------|
| ~SPC m ​,​~ and ~SPC m c~ | Valid/Confirm the message |
| ~SPC m a~ and ~SPC m k~ | Abort/Discard the message |

Some example of these modes are =magit= commit messages, =message-mode= for
mails or =org-mode= notes.

** Evaluation
Live evaluation of code is under the prefix ~SPC m e~.

| Key     | Description                                   |
|---------+-----------------------------------------------|
| ~m e $~ | put point at the end of the line and evaluate |
| ~m e b~ | evaluate buffer                               |
| ~m e e~ | evaluate last expression                      |
| ~m e f~ | evaluate function                             |
| ~m e l~ | evaluate line                                 |
| ~m e r~ | evaluate region                               |

** REPLs
*** Send code
A lot of languages can interact with a REPL. To help keeping a
consistent behavior between those languages the following conventions
should be followed:
- ~SPC m s~ is the prefix for sending code. This allows fast interaction with
  the REPL whenever it is possible
- lower case key bindings keep the focus on the current buffer
- upper case key bindings move the focus to the REPL buffer

| Key     | Description                                                  |
|---------+--------------------------------------------------------------|
| ~m s b~ | send buffer                                                  |
| ~m s B~ | send buffer and switch to REPL                               |
| ~m s d~ | first key to send buffer and switch to REPL to debug (step)  |
| ~m s D~ | second key to send buffer and switch to REPL to debug (step) |
| ~m s f~ | send function                                                |
| ~m s F~ | send function and switch to REPL                             |
| ~m s i~ | start/switch to REPL inferior process                        |
| ~m s l~ | send line                                                    |
| ~m s L~ | send line and switch to REPL                                 |
| ~m s r~ | send region                                                  |
| ~m s R~ | send region and switch to REPL                               |

Note: we don't distinguish between the file and the buffer.

*** In terminal
History navigation in shells or REPLs buffers should be bound as well to
~C-j~ and ~C-k~.

| Key   | Description                |
|-------+----------------------------|
| ~C-j~ | next item in history       |
| ~C-k~ | previous item in history   |
| ~C-l~ | clear screen               |
| ~C-r~ | search backward in history |

** Building and Compilation
The base prefix for major mode specific compilation is ~SPC m c~.

| Key binding | Description       |
|-------------+-------------------|
| ~m c b~     | compile buffer    |
| ~m c c~     | compile           |
| ~m c C~     | clean             |
| ~m c r~     | clean and compile |

Note: we don't distinguish between the file and the buffer. We can
implement an auto-save of the buffer before compiling the buffer.

** Debugging
The base prefix for debugging commands is ~SPC m d~.

| Key binding | Description             |
|-------------+-------------------------|
| ~m d a~     | abandon current process |
| ~m d b~     | toggle a breakpoint     |
| ~m d B~     | clear all breakpoints   |
| ~m d c~     | continue                |
| ~m d d~     | start debug session     |
| ~m d i~     | step in                 |
| ~m d l~     | local variables         |
| ~m d o~     | step out                |
| ~m d r~     | run                     |
| ~m d s~     | next step               |
| ~m d v~     | inspect value at point  |

Notes:
- Ideally a transient-state for breakpoint navigation should be provided.
- If there is no toggle breakpoint function, then it should be implemented at
  the spacemacs level and ideally the function should be proposed as a patch
  upstream (major mode repository).

** Errors
Management of errors should be put under ~SPC m E~.

| Key binding | Description                         |
|-------------+-------------------------------------|
| ~m E e~     | fix error around point              |
| ~m E l~     | show errors                         |
| ~m E L~     | show errors and jump to errors list |

** Plain Text Markup Languages
For layers supporting markup languages please follow the following
keybindings whenever applicable.

*** Headers
All header functionality should be grouped under ~SPC m h~

| Key binding | Description                                      |
|-------------+--------------------------------------------------|
| ~m h i~     | Insert a header                                  |
| ~m h I~     | Insert a header alternative method (if existing) |
| ~m h 1..10~ | Insert a header of level 1..10 (if possible)     |

*** Insertion of common elements
Insertion of common elements like links or footnotes should be grouped
under ~SPC m i~

| Key binding | Description      |
|-------------+------------------|
| ~m i f~     | Insert footnote  |
| ~m i i~     | Insert image     |
| ~m i l~     | Insert link      |
| ~m i u~     | Insert url       |
| ~m i w~     | Insert wiki-link |

*** Text manipulation
Manipulation of text regions should be grouped under ~SPC m x~

| Key binding | Description                   |
|-------------+-------------------------------|
| ~m x b~     | Make region bold              |
| ~m x c~     | Make region code              |
| ~m x i~     | Make region italic            |
| ~m x q~     | Quote a region                |
| ~m x r~     | Remove formatting from region |
| ~m x s~     | Make region strike-through    |
| ~m x u~     | Make region underlined        |
| ~m x v~     | Make region verbatim          |

*** Movement in normal mode
In normal mode Vim style movement should be enabled with these key bindings:

| Key binding | Description                            |
|-------------+----------------------------------------|
| ~g h~       | Move up one level in headings          |
| ~g j~       | Move to next heading on same level     |
| ~g k~       | Move to previous heading on same level |
| ~g l~       | Move down one level in headings        |

*** Promotion, Demotion and element movement
Promotion, demotion and movement of headings or list elements (whatever is
possible) should be enabled with the following keys when in Vim style or
Hybrid with hjkl movements enabled:

| Key binding | Description                  |
|-------------+------------------------------|
| ~M-h~       | Promote heading by one level |
| ~M-j~       | Move element down            |
| ~M-k~       | Move element up              |
| ~M-l~       | Demote heading by one level  |

In all editing styles promotion and demotion can be done with the following
keys:

| Key binding | Description                  |
|-------------+------------------------------|
| ~M-down~    | Move element down            |
| ~M-left~    | Promote heading by one level |
| ~M-right~   | Demote heading by one level  |
| ~M-up~      | Move element up              |

*** Table editing
If table specific commands are available the they are grouped under the
~SPC m t~ group.

** Tests
A lot of languages have their own test frameworks. These frameworks
share common actions that we can unite under the same key bindings:
- ~SPC m t~ is the prefix for test execution.
- ~SPC m t g~ is the prefix for test generation.
- ~SPC m t X~ is used to execute ~SPC m t x~ but in debug mode (if supported).

*** All languages

| Key     | Description                                                  |
|---------+--------------------------------------------------------------|
| ~m t a~ | execute all the tests of the current project                 |
| ~m t A~ | execute all the tests of the current project in debug        |
| ~m t b~ | execute all the tests of the current buffer                  |
| ~m t B~ | execute all the tests of the current buffer in debug         |
| ~m t l~ | execute the last executed test again                         |
| ~m t t~ | execute the current test (thing at point, function)          |
| ~m t T~ | execute the current test in debug (thing at point, function) |

Note: we don't distinguish between the file and the buffer. We can
implement an auto-save of the buffer before executing the tests of
buffer.

*** Language specific

| Key     | Description                                      |
|---------+--------------------------------------------------|
| ~m t m~ | execute the tests of the current module          |
| ~m t M~ | execute the tests of the current module in debug |
| ~m t s~ | execute the tests of the current suite           |
| ~m t S~ | execute the tests of the current suite in debug  |

Note that there are overlaps, depending on the language we will choose
one or more bindings for the same thing

** Toggles
- Global toggles are under ~SPC t~, ~SPC T~ and ~SPC C-t~
- Major mode toggles are only under ~SPC m T~

** Refactoring
Refactoring prefix is ~SPC m r~.

** Imports
When =import= management is supported the following key bindings should be used:

| Key binding | Description                        |
|-------------+------------------------------------|
| ~m i i~     | add import for symbol around point |
| ~m i f~     | fix/format imports                 |
| ~m g i~     | go to imports                      |

** Code Formatting
Major-mode code formatting is under prefix ~SPC m =~.

| Key binding | Description              |
|-------------+--------------------------|
| ~m = =~     | format thing under point |
| ~m = b~     | format current buffer    |
| ~m = f~     | format current function  |

** Web frameworks
Web frameworks key bindings should go under ~SPC m f~.

** Help or Documentation
The base prefix for help commands is ~SPC m h~. Documentation is considered
as an help command.

| Key     | Description                        |
|---------+------------------------------------|
| ~m h h~ | documentation of thing under point |
| ~m h r~ | documentation of selected region   |

* Writing documentation
Spacemacs provides an example layer =README.org= file in
=~/.emacs.d/core/templates/README.org.template=.

** Spacing in documentation
- Spacemacs tries to keep the documentation consistent between all layers by
  providing some rules for spacing:
  - After each header, you should not add an empty line
    - *Exception*: If the first item under the header is a table, add an empty
      line after it
  - At the end of each header node, there should be an empty line
  - Note: Many layer =READMEs= do not follow this convention yet. Please fix
    them if you can.
- To keep things readable only mention the prefix ~SPC~ when documenting
  key bindings, you don't need to mention ~M-m~.
