electric-case.el

camelCase、snake_case の識別子を Shift キーなしで入力

insert camelCase and snake_case words, without “Shift”ing

Screencast

Installation

Load this script

(require 'electric-case)

and initialize in major-mode hooks.

(add-hook 'java-mode-hook 'electric-case-java-init)

And when you type the following in java-mode for example,

public class test-class{
    public void test-method(void){

electric-case automatically converts it into :

public class TestClass{
    public void testMethod(void){

Preconfigured settings for some other languages are also provided. Try:

(add-hook 'c-mode-hook electric-case-c-init)
(add-hook 'ahk-mode-hook electric-case-ahk-init)
(add-hook 'scala-mode-hook electric-case-scala-init)

To add support for other languages, please read section 2.

Customization

electric-case-convert-calls

electric-case do not convert other expressions than declarations by default. To enable conversion for other expressions, set electric-case-convert-calls non-nil.

(setq electric-case-convert-calls t)

This sometimes produces confusing results for novice users. For example,

foo-bar

does not mean “foo minus bar”, but is converted to

fooBar

To make “-” counted as a subtraction or negation, insert whitespace around it.

foo - bar

I recommend to keep electric-case-convert-calls nil, because it is a kind of overkill. Once you declared a symbol, the symbol can be inserted easily using completion. This script is useful when you TYPE BY HAND camel-case or snake-case symbols. But in case you do not need to type, not to type seems much better.

electric-case-convert-nums/beginning/end

Even if electric-case-convert-calls is non-nil, numbers and hyphens at beginning/end of symbols are not converted.

-foo-1  =>  -foo-1

You may change this behavior by setting some of three variables to non-nil.

(setq electric-case-convert-nums t)      hyphens around numbers
(setq electric-case-convert-beginning t) hyphens at beginning of symbols
(setq electric-case-convert-end t)       hyphens at end of symbols

When you insert an expression “-foo–1–bar-“,

                +---num
                |     +--- num
                V     V
 -  f  o  o  -  -  1  -  -  b  a  r  -
 ^           ^           ^           ^
 |           +--- end    |           +--- end
 +--- beginning          +--- beginning

electric-case will convert as follows:

Overlays

Symbols that may be converted by electric-case are shadowed by default. If this is not comfortable for you, evaluate following expression to disable it.

(setq electric-case-pending-overlay nil)

Or you may also choose another face to highlight pending symbols, that looks better in your color-scheme.

(setq electric-case-pending-overlay 'highlight)

Implementing Language Supports

There are two important buffer-local variables:

• electric-case-criteria

  A function that defines which case to convert the symbol into. The function will be given 2 arguments: the beginning and the end point of the symbol. The function must return one of camel, ucamel, snake, usnake, or nil. When the return value is nil, the symbol is not converted.

  Remember, that if electric-case-convert-calls is nil, symbols not in declarations are not expected to be converted. electric-case does not know whether the symbol is in a declaration or not, so criteria functions must be aware of it.

  Here is an example:

  (setq electric-case-criteria
        (lambda (b e n)
          (let ((proper (text-properties-at b)))
            (cond ((member 'font-lock-function-name-face proper) 'snake)
                  ((member 'font-lock-variable-name-face proper)
                   (if (member '(cpp-macro) (c-guess-basic-syntax))
                       'usnake 'snake))
                  (electric-case-convert-calls 'snake)
                  (t nil)))))
      

  With the criteria function above, function-declarations and variable-declarations are converted into snake_case. Macro declarations are converted into UP_SNAKE_CASE. Other symbols are converted into snake_case, if and only if electric-case-convert-calls is non-nil. This may be one of the minimal criteria functions for C-like language.

• electric-case-max-iteration

  For example, in Java, the syntactic category of the symbol “what-is-this” below is not decidable.

  what-is-this
      

  But when ” symbol;” is added, now “what-is-this” is a class name.

  what-is-this symbol;
      

  So electric-case can convert it.

  WhatIsThis symbol;
      

  In this example, the symbol “what-is-this” must be checked twice. So, electric-case-max-iteration for Java must be 2 or greater. Otherwise, “what-is-this” is not checked twice, and is not converted.

Known Bugs:

• class name that ends with “Class” is treated as keyword “class”