Demo

About

multi-line aims to provide a flexible framework for automatically multi-lining and single-lining function invocations and definitions, array and map literals and more. It relies on functions that are defined on a per major mode basis wherever it can so that it operates correctly across many different programming languages.

Supported Languages

The following languages are officially supported by multi-line

C/C++
clojure
emacs-lisp
golang
java
javascript
python
ruby
rust
scala

It is likely that multi-line will function pretty well in any language using typical brace/parenthesis/comma syntax, provided that the major mode has properly defined forward-sexp and indent-line. If you find that multi-line works well without modification in your language of choice please file an issue or submit a pull request to have it added to the list of officially supported languages.

Installation

Install from MELPA with M-x package-install multi-line. See the melpa repository for details about how to set up MELPA if you have not already done so.

Setup

(require 'multi-line)
(global-set-key (kbd "C-c d") 'multi-line)

Usage

Execute the multi-line command (with M-x or a keybinding) inside the body of the expression you wish to multi-line, as show in the demo above. Invoking multi-line multiple times on the same definition will cycle between the different respacing styles that are configured for the current buffer.

When invoked with a prefix argument (C-u), multi-line will “single-line” the expression at point, removing all new lines and replacing them with spaces (or the character configured for single lining).

Configuration

multi-line can be configured to behave differently depending on the major mode of the current-buffer. The behavior of multi-line is described with a multi-line-strategy object that has three components: a find-strategy, an enter-strategy and a replace-strategy. The multi-line-defhook macro can be used to set a major mode specific multi-lining strategy. The strategy defined with the defhook will become active in any buffers with the specified mode.

In the following example we set the default multi-lining behavior for the clojure programming language.

(multi-line-defhook clojure
  (make-instance multi-line-strategy
   :find (make-instance multi-line-forward-sexp-find-strategy
          :split-regex "[[:space:]\n]+"
          :done-regex "[[:space:]]*)]}"
          :split-advance-fn 'multi-line-lisp-advance-fn)
   :respace multi-line-lisp-respacer))

This expands to

(eval-and-compile
  (defvar multi-line-clojure-strategy)
  (setq multi-line-clojure-strategy
        (make-instance multi-line-strategy
                       :find
                       (make-instance multi-line-forward-sexp-find-strategy
                                      :split-regex "[[:space:]]+"
                                      :done-regex "[[:space:]]*)]}"
                                      :split-advance-fn 'multi-line-lisp-advance-fn)
                       :respace multi-line-lisp-respacer))
  (defun multi-line-clojure-mode-hook nil
    (setq-local multi-line-current-strategy multi-line-clojure-strategy))
  (add-hook 'clojure-mode-hook 'multi-line-clojure-mode-hook t))

Users will most often want to configure the respacing portion of the multi-line strategy. If you prefer to always add a newline at every available split point you might set up the default multi-line strategy as follows:

(setq-default multi-line-current-strategy
              (multi-line-strategy
               :respace (multi-line-default-respacers
                         (make-instance multi-line-always-newline))))

Built-in Mode Specific Behavior

multi-line has some built in mode specific behavior that is enabled by default. The interactive function multi-line-disable-mode-hooks disables this mode specific behavior.