pentadactyl-pm/HACKING

= Hacking =

If you've taken to hacking Pentadactyl source code, we hope that you'll share
your changes. In case you do, please keep the following in mind, and we'll be
happy to accept your patches.

== Documentation ==

First of all, all new features and all user-visible changes to existing
features need to be documented. That means editing the appropriate help files
and adding a NEWS entry where appropriate. When editing the NEWS file, you
should add your change to the top of the list of changes. If your change
alters an interface (key binding, command) and is likely to cause trouble,
prefix it with 'IMPORTANT:', otherwise, place it below the other 'IMPORTANT'
entries. If you're not sure if your change merits a news entry, or if it's
important, please ask.

== Coding Style ==

In general: Just look at the existing source code!

We try to target experienced JavaScript developers who do not
necessarily need to have a good understanding of Pentadactyl's source
code, nor necessarily understand in-depth concepts of other
languages like Lisp or Python.  Therefore, the coding style should
feel natural to any JavaScript developer.  Of course, this does not
mean, you have to avoid all new JavaScript features like list
comprehension or generators.  Use them, when they make sense, but
don't use them when the resulting code is hard to read.

=== The most important style issues are: ===

* Use 4 spaces to indent things, no tabs, not 2, nor 8 spaces. If you use Vim,
  this should be taken care of automatically by the modeline (like the
  one below).

* No trailing whitespace.

* Use " for enclosing strings instead of ', unless using ' avoids escaping of lots of "
  Example: alert("foo") instead of alert('foo');

* Use // regexp literals rather than RegExp constructors, unless
  you're constructing an expression on the fly, or RegExp
  constructors allow you to escape less /s than the additional
  escaping of special characters required by string quoting.

  Good: /application\/xhtml\+xml/
  Bad:  RegExp("application/xhtml\\+xml")
  Good: RegExp("http://(www\\.)vimperator.org/(.*)/(.*)")
  Bad:  /http:\/\/(www\.)vimperator.org\/(.*)\/(.*)/

* Exactly one space after if/for/while/catch etc. and after a comma, but none
  after a parenthesis or after a function call:
      for (pre; condition; post)
  but:
      alert("foo");

* Bracing is formatted as follows:
    function myFunction () {
        if (foo)
            return bar;
        else {
            baz = false;
            return baz;
        }
    }
    var quux = frob("you",
        {
            a: 1,
            b: 42,
            c: {
                hoopy: "frood"
            }
        });

  When in doubt, look for similar code.

* No braces for one-line conditional statements:
  Right:
     if (foo)
         frob();
     else
         unfrob();

* Prefer lambda-style functions where suitable:
  Right: list.filter(function (elem) elem.good != elem.BAD);
  Wrong: list.filter(function (elem) { return elem.good != elem.BAD });
  Right: list.forEach(function (elem) { window.alert(elem); });
  Wrong: list.forEach(function (elem) window.alert(elem));

* Anonymous function definitions should be formatted with a space after the
  keyword "function". Example: function () {}, not function() {}.

* Prefer the use of let over var i.e. only use var when required.
  For more details, see
  https://developer.mozilla.org/en/New_in_JavaScript_1.7#Block_scope_with_let

* Reuse common local variable names E.g. "elem" is generally used for element,
  "win" for windows, "func" for functions,  "ret" for return values etc.

* Prefer // over /* */ comments (exceptions for big comments are usually OK)
  Right: if (HACK) // TODO: remove hack
  Wrong: if (HACK) /* TODO: remove hack */

* Documentation comment blocks use /** ... */ Wrap these lines at 80
  characters.

* Only wrap lines if it makes the code obviously clearer. Lines longer than 132
  characters should probably be broken up rather than wrapped anyway.

* Use UNIX new lines (\n), not windows (\r\n) or old Mac ones (\r)

* Use Iterators or Array#forEach to iterate over arrays. for (let i
  in ary) and for each (let i in ary) include members in an
  Array.prototype, which some extensions alter.
  Right:
    for (let [,elem] in Iterator(ary))
    for (let [k, v] in Iterator(obj))
    ary.forEach(function (elem) { ...
  Wrong:
    for each (let elem in ary)

  The exceptions to this rule are for objects with __iterator__ set,
  and for XML objects (see README.E4X).

* Avoid using 'new' with constructors where possible, and use [] and
  {} rather than new Array/new Object.
  Right:
    RegExp("^" + foo + "$")
    Function(code)
    new Date
  Wrong:
    new RegExp("^" + foo + "$")
    new Function(code)
    Date() // Right if you want a string-representation of the date

* Don't use abbreviations for public methods
  Right:
    function splitString()...
    let commands = ...;
    let cmds = ...; // Since it's only used locally, abbreviations are ok, but so are the full names
  Wrong:
    function splitStr()

== Testing/Optimization ==

TODO: Add some information here about testing/validation/etc.
Information about how/when to use :regressions might be nice.
Additionally, maybe there should be some benchmark information here --
something to let a developer know what's "too" slow...? Or general
guidelines about optimization?

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