Add sourceMapIn option

This closes gruntjs#231

.gitignore

@@ -1,3 +1,4 @@
 node_modules
 npm-debug.log
-tmp
+tmp
+tmp2

AUTHORS

@@ -4,3 +4,4 @@ Thomas Boyt (http://www.thomasboyt.com/)
 Liam Kaufman (http://liamkaufman.com/)
 Jörn Zaefferer (http://bassistance.de)
 Braden Anderson (http://google.com/profiles/bluej100)
+Meinaart van Straalen (http://github.com/meinaart)

CHANGELOG

@@ -1,3 +1,7 @@
+v0.15.0:
+  date: 2016-01-19
+  changes:
+    - added sourceMapIn option
 v0.14.0:
   date: 2015-09-15
   changes:

Gruntfile.js

@@ -53,6 +53,30 @@ module.exports = function (grunt) {
             'test/fixtures/inner/input_inline_import.css'
           ]
         }
+      },
+      sourceMapIn: {
+        options: {
+          sourceMap: true,
+          sourceMapInlineSources: true,
+          sourceMapIn: true
+        },
+        files: [{
+          src: [absolutePath('test/fixtures/sourcemap.css')],
+          dest: absolutePath('tmp/sourcemap.css')
+        }]
+      },
+      sourceMapInFunction: {
+        options: {
+          sourceMap: true,
+          sourceMapInlineSources: true,
+          sourceMapIn: function(filename) {
+            return grunt.file.read(filename + '.map', {encoding: 'utf8'});
+          }
+        },
+        files: [{
+          src: [absolutePath('test/fixtures/sourcemap.css')],
+          dest: absolutePath('tmp2/sourcemap.css')
+        }]
       }
     },
     nodeunit: {

README.md

@@ -50,6 +50,18 @@ Default: `false`
 
 Enable Source Maps.
 
+#### sourceMapIn
+
+Type: `boolean`, `function`  
+Choices: `true`, `false`, `function`
+Default: `undefined`
+
+Method for processing existing sourceMap. When set to true `cssmin` looks for the location of the sourceMap by parsing the `sourceMappingURL` and reading that file from disk (relative to input CSS file).
+
+When a function is supplied cssmin calls this function with the filename of the input CSS file as argument. The function is expected to return a value that is supplied to `clean-css` as `sourceMap` argument. See [clean-css documentation](https://github.com/jakubpawlowicz/clean-css#how-to-use-clean-css-api) for further explanation.
+
+Note: this property only works when `sourceMap` is also set to true.
+
 ### Usage
 
 #### Combine two files into one output file
@@ -115,4 +127,4 @@ cssmin: {
 
 Task submitted by [Tim Branyen](http://tbranyen.com/)
 
-*This file was generated on Tue Sep 15 2015 10:19:12.*
+*This file was generated on Tue Jan 19 2016 09:11:31.*

package.json

@@ -1,7 +1,7 @@
 {
   "name": "grunt-contrib-cssmin",
   "description": "Minify CSS",
-  "version": "0.14.0",
+  "version": "0.15.0",
   "author": {
     "name": "Grunt Team",
     "url": "http://gruntjs.com/"

tasks/cssmin.js

@@ -41,6 +41,24 @@ module.exports = function (grunt) {
       options.relativeTo = path.dirname(availableFiles[0]);
 
       try {
+        if(options.sourceMap && options.sourceMapIn) {
+          if(typeof options.sourceMapIn === 'function') {
+            options.sourceMap = options.sourceMap && options.sourceMapIn(availableFiles[0]);
+          } else if(options.sourceMapIn === true) {
+            var content = grunt.file.read(availableFiles[0], {encoding: 'utf8'});
+            var sourceMapMatch = content.match(/sourceMappingURL\=([^ ]*)/);
+            if(sourceMapMatch && sourceMapMatch.length === 2) {
+              var sourceMap = sourceMapMatch[1];
+              if(sourceMap.indexOf('/') === -1 || sourceMap.indexOf('/') > 0) {
+                sourceMap = options.relativeTo + '/' + sourceMap;
+                if(grunt.file.exists(sourceMap)) {
+                  options.sourceMap = grunt.file.read(sourceMap, {encoding: 'utf8'});
+                }
+              }
+            }
+          }
+        }
+
         compiled = new CleanCSS(options).minify(availableFiles);
 
         if (compiled.errors.length) {

test/test.js

@@ -6,32 +6,47 @@ function readFileAndRemoveNewlines(file) {
   return grunt.file.read(file).replace(/\n/g, '');
 }
 
+function filesEqual(test, filename, filename2, message) {
+  var expect = readFileAndRemoveNewlines(filename);
+  var result = readFileAndRemoveNewlines(filename2);
+  test.equal(expect, result, message);
+}
+
+function testFilesEqual(test, filename, message) {
+  return filesEqual(test, 'test/expected/' + filename, 'tmp/' + filename, message);
+}
+
 exports.cssmin = {
   main: function(test) {
     test.expect(1);
-
-    var expect = readFileAndRemoveNewlines('test/expected/style.css');
-    var result = readFileAndRemoveNewlines('tmp/style.css');
-    test.equal(expect, result, 'should concat and minify an array of CSS files in order using clean-css');
-
+    testFilesEqual(test, 'style.css',
+      'should concat and minify an array of CSS files in order using clean-css');
     test.done();
   },
   imports: function(test) {
     test.expect(1);
-
-    var expect = readFileAndRemoveNewlines('test/expected/inline_import.css');
-    var result = readFileAndRemoveNewlines('tmp/inline_import.css');
-    test.equal(expect, result, 'should inline @import');
-
+    testFilesEqual(test, 'inline_import.css', 'should inline @import');
     test.done();
   },
   absolute: function(test) {
     test.expect(1);
-
-    var expect = readFileAndRemoveNewlines('test/expected/absolute.css');
-    var result = readFileAndRemoveNewlines('tmp/absolute.css');
-    test.equal(expect, result, 'should perform the standard tasks when given absolute paths');
-
+    testFilesEqual(test, 'absolute.css', 'should perform the standard tasks when given absolute paths');
+    test.done();
+  },
+  sourceMapIn: function(test) {
+    test.expect(3);
+    testFilesEqual(test, 'sourcemap.css', 'should have correct format with sourceMappingURL');
+    test.ok(grunt.file.exists('tmp/sourcemap.css.map'), 'sourceMap file should exist');
+    testFilesEqual(test, 'sourcemap.css.map', 'sourceMap should have correct format');
+    test.done();
+  },
+  sourceMapInFunction: function(test) {
+    test.expect(3);
+    filesEqual(test, 'test/expected/sourcemap.css', 'tmp2/sourcemap.css',
+      'should have correct format with sourceMappingURL');
+    test.ok(grunt.file.exists('tmp2/sourcemap.css.map'), 'sourceMap file should exist');
+    filesEqual(test, 'test/expected/sourcemap.css.map', 'tmp2/sourcemap.css.map',
+      'sourceMap should have correct format');
     test.done();
   }
 };