Adding a backwards compatible node-style callback

This is node-style callbacks for #676. This allows us to release
the new callback style without introducing backwards incompatible
changes (or making changes to the binary from 2.0.1). If a node style
callback is provided, it will be used. For now, this stacks with
the original `options.success` and `options.error`, although it can
be trivially changed to an xor.

To highlight the new interface, a separate `describe` was added to the
tests which identifies the `{options}, cb` interface and tests it
independently.

README.md

@@ -54,9 +54,8 @@ Compiling versions 0.9.4 and above on Windows machines requires [Visual Studio 2
 var sass = require('node-sass');
 sass.render({
 	file: scss_filename,
-	success: callback
 	[, options..]
-	});
+}, function(err, result) { /*...*/ });
 // OR
 var result = sass.renderSync({
 	data: scss_content
@@ -66,7 +65,7 @@ var result = sass.renderSync({
 
 ### Options
 
-The API for using node-sass has changed, so that now there is only one variable - an options hash. Some of these options are optional, and in some circumstances some are mandatory.
+The API for using node-sass has changed, so that now there is only one options hash. In the options hash, some items are optional, others may be mandatory depending on circumstances.
 
 #### file
 `file` is a `String` of the path to an `scss` file for [libsass] to render. One of this or `data` options are required, for both render and renderSync.
@@ -140,6 +139,26 @@ You must define this option as well as `outFile` in order to generate a source m
 #### sourceMapContents
 `sourceMapContents` is a `Boolean` flag to determine whether to include `contents` in maps.
 
+### The `render` Callback (starting from v2.1)
+node-sass supports standard node style asynchronous callbacks with the signature of `function(err, result)`. In error conditions, the `error` argument is populated with the error object. In success conditions, the `result` object is populated with an object describing the result of the render call.
+
+#### The Error Object
+* `message` - The error message.
+* `line` - The line number of error.
+* `column` - The column number of error.
+* `status` - The status code.
+* `file` - The filename of error. In case `file` option was not set (in favour of `data`), this will reflect the value `stdin`.
+
+#### The Result Object
+* `css` - The compiled CSS. Write this to a file, or serve it out as needed.
+* `map` - The source map
+* `stats` - An object containing information about the compile. It contains the following keys:
+  * `entry` - The path to the scss file, or `data` if the source was not a file
+  * `start` - Date.now() before the compilation
+  * `end` - Date.now() after the compilation
+  * `duration` - *end* - *start*
+  * `includedFiles` - Absolute paths to all related scss files in no particular order.
+
 ### Examples
 
 ```javascript
@@ -176,6 +195,10 @@ sass.render({
 	},
 	includePaths: [ 'lib/', 'mod/' ],
 	outputStyle: 'compressed'
+}, function(error, result) {
+  // starting v2.1 the node-style callback has error (Object) and result (Object)
+  // the objects are identical to those provided for the error and success keys
+  // in the options object
 });
 // OR
 var result = sass.renderSync({

lib/index.js

@@ -127,7 +127,7 @@ function getSourceMap(options) {
  * @param {Object} options
  * @api private
  */
-function getOptions(options) {
+function getOptions(options, cb) {
   options = options || {};
   options.comments = options.source_comments || options.sourceComments || false;
   options.data = options.data || null;
@@ -150,21 +150,30 @@ function getOptions(options) {
   var success = options.success;
 
   options.error = function(err) {
+    var payload = util._extend(new Error(), JSON.parse(err));
+
+    if (cb) {
+      cb.call(options.context, payload, null);
+    }
     if (error) {
-      error.call(options.context, util._extend(new Error(), JSON.parse(err)));
+      error.call(options.context, payload);
     }
   };
 
   options.success = function() {
     var result = options.result;
     var stats = endStats(result.stats);
-
-    if (success) {
-      success.call(options.context, {
+    var payload = {
       css: result.css,
       map: result.map,
       stats: stats
-      });
+    };
+
+    if (cb) {
+      cb.call(options.context, null, payload);
+    }
+    if (success) {
+      success.call(options.context, payload);
     }
   };
 
@@ -194,8 +203,8 @@ var binding = require(getBinding());
  * @api public
  */
 
-module.exports.render = function(options) {
-  options = getOptions(options);
+module.exports.render = function(options, cb) {
+  options = getOptions(options, cb);
 
   var importer = options.importer;
 
@@ -243,7 +252,6 @@ module.exports.renderSync = function(options) {
 
   if(status) {
     result.stats = endStats(result.stats);
-
     return result;
   }
 

test/api.js

@@ -411,6 +411,28 @@ describe('api', function() {
     });
   });
 
+  describe('.render(options, cb)', function() {
+    it('should compile sass to css with file', function(done) {
+      var expected = 'div {\n  color: yellow; }';
+      sass.render({
+        data: 'div {color: yellow;}'
+      }, function(err, result) {
+        assert.equal(result.css.trim(), expected);
+        done();
+      });
+    });
+
+    it('should throw error status 1 for bad input', function(done) {
+      sass.render({
+        data: '#navbar width 80%;'
+      }, function(err) {
+        assert(err.message);
+        assert.equal(err.status, 1);
+        done();
+      });
+    });
+  });
+
   describe('.renderSync(options)', function() {
     it('should compile sass to css with file', function(done) {
       var expected = read(fixture('simple/expected.css'), 'utf8').trim();