See clean-css#7 - adds a beforeMinify CLI callback.

Why:

* When used as a module a custom CLI implementation can hook into
  pre-minify configuration and alter it;
* it may be useful as a way of customizing CLI beyond command line
  arguments.

Author: jakubpawlowicz

index.js

@@ -4,15 +4,17 @@ var path = require('path');
 var CleanCSS = require('clean-css');
 var commands = require('commander');
 
-function cli(process) {
-  var packageConfig = fs.readFileSync(path.join(path.dirname(fs.realpathSync(process.argv[1])), '../package.json'));
+function cli(process, beforeMinifyCallback) {
+  var packageConfig = fs.readFileSync(path.join(__dirname, 'package.json'));
   var buildVersion = JSON.parse(packageConfig).version;
   var fromStdin;
   var debugMode;
   var options;
   var stdin;
   var data;
 
+  beforeMinifyCallback = beforeMinifyCallback || Function.prototype;
+
   // Specify commander options to parse command line params correctly
   commands
     .version(buildVersion, '-v, --version')
@@ -153,7 +155,7 @@ function cli(process) {
 
   // ... and do the magic!
   if (commands.args.length > 0) {
-    minify(process, options, debugMode, commands.args);
+    minify(process, beforeMinifyCallback, options, debugMode, commands.args);
   } else {
     stdin = process.openStdin();
     stdin.setEncoding('utf-8');
@@ -162,7 +164,7 @@ function cli(process) {
       data += chunk;
     });
     stdin.on('end', function () {
-      minify(process, options, debugMode, data);
+      minify(process, beforeMinifyCallback, options, debugMode, data);
     });
   }
 }
@@ -195,8 +197,11 @@ function findArgumentTo(option, rawArgs, args) {
   return value;
 }
 
-function minify(process, options, debugMode, data) {
-  new CleanCSS(options).minify(data, function (errors, minified) {
+function minify(process, beforeMinifyCallback, options, debugMode, data) {
+  var cleanCss = new CleanCSS(options);
+
+  beforeMinifyCallback(cleanCss);
+  cleanCss.minify(data, function (errors, minified) {
     var mapFilename;
 
     if (debugMode) {

test/binary-test.js

@@ -612,4 +612,14 @@ vows.describe('cleancss')
       })
     }
   })
+  .addBatch({
+    'custom CLI': {
+      'topic': function () {
+        exec('echo ".block{background-image:url(image.png)}" | ./test/custom-cli/custom-cleancss', this.callback);
+      },
+      'outputs transformed url': function (error, stdout) {
+        assert.equal(stdout, '.block{background-image:url(../valid/path/to/image.png)}');
+      }
+    }
+  })
   .export(module);

test/custom-cli/custom-cleancss

@@ -0,0 +1,10 @@
+#!/usr/bin/env node
+
+var cleanCssCli = require('../../index');
+return cleanCssCli(process, function (cleanCss) {
+  cleanCss.options.level['1'].transform = function (propertyName, propertyValue) {
+    if (propertyName == 'background-image' && propertyValue.indexOf('../valid/path/to') == -1) {
+      return propertyValue.replace('url(', 'url(../valid/path/to/');
+    }
+  }
+});