From e545d67f2a86b04e28e20624dc3f74e8b9bc0657 Mon Sep 17 00:00:00 2001
From: Vitaliy Ribachenko <vit@ribachenko.com>
Date: Wed, 4 Jan 2017 15:17:15 +0200
Subject: [PATCH 1/2] Add sequential options which allows process files one
 after another

---
 README.md        |  7 ++++++
 tasks/postcss.js | 63 ++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 65 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index ae6c6e4..6f07db7 100644
--- a/README.md
+++ b/README.md
@@ -94,6 +94,13 @@ options: {
 ```
 You can also specify a path where you want the file to be saved.
 
+#### options.sequential
+Type: `Boolean`
+Default value: `false`
+
+By default grunt-postcss will load all passed CSS files and immediately process them. Set this to `true` if you want files to be processed one by one. 
+This can help in case when you have a lot of CSS files and processing them causes an `out of memory` error.
+
 #### options.failOnError
 Type: `Boolean`
 Default value: `false`
diff --git a/tasks/postcss.js b/tasks/postcss.js
index 09101f1..2ea5609 100644
--- a/tasks/postcss.js
+++ b/tasks/postcss.js
@@ -9,6 +9,7 @@ var maxmin = require('maxmin');
 module.exports = function(grunt) {
     var options;
     var processor;
+    var tasks;
 
     /**
      * Returns an input map contents if a custom map path was specified
@@ -55,7 +56,7 @@ module.exports = function(grunt) {
      * @param {string} input Input CSS contents
      * @param {string} from Input CSS path
      * @param {string} to Output CSS path
-     * @returns {{css: string, map: ?string}}
+     * @returns {LazyResult}
      */
     function process(input, from, to) {
         return processor.process(input, {
@@ -73,6 +74,57 @@ module.exports = function(grunt) {
         });
     }
 
+    /**
+     * Runs tasks sequentially
+     * @returns {Promise}
+     */
+    function runSequence() {
+        if (!tasks.length) {
+            return Promise.resolve();
+        }
+
+        var currentTask = tasks.shift();
+
+        return process(currentTask.input, currentTask.from, currentTask.to).then(function(result) {
+            currentTask.cb(result);
+            currentTask = null;
+            return runSequence();
+        });
+    }
+
+    /**
+     * Creates a task to be processed
+     * @param {string} input
+     * @param {string} from
+     * @param {string} to
+     * @param {Function} cb
+     * @returns {Promise|Object}
+     */
+    function createTask(input, from, to, cb) {
+        var newTask;
+
+        if (options.sequential) {
+            newTask = {
+                input: input,
+                from: from,
+                to: to,
+                cb: cb
+            };
+        } else {
+            newTask = process(input, from, to).then(cb);
+        }
+
+        return newTask;
+    }
+
+    /**
+     * Runs prepared tasks
+     * @returns {Promise}
+     */
+    function runTasks() {
+        return options.sequential ? runSequence() : Promise.all(tasks);
+    }
+
     /**
      * @param {string} msg Log message
      */
@@ -87,8 +139,10 @@ module.exports = function(grunt) {
             diff: false,
             safe: false,
             failOnError: false,
-            writeDest: true
+            writeDest: true,
+            sequential: false
         });
+        tasks = [];
 
         var tally = {
             sheets: 0,
@@ -107,7 +161,6 @@ module.exports = function(grunt) {
         }
 
         var done = this.async();
-        var tasks = [];
 
         this.files.forEach(function(f) {
             var src = f.src.filter(function(filepath) {
@@ -130,7 +183,7 @@ module.exports = function(grunt) {
                 var dest = f.dest || filepath;
                 var input = grunt.file.read(filepath);
 
-                return process(input, filepath, dest).then(function(result) {
+                return createTask(input, filepath, dest, function(result) {
                     var warnings = result.warnings();
 
                     tally.issues += warnings.length;
@@ -172,7 +225,7 @@ module.exports = function(grunt) {
             }));
         });
 
-        Promise.all(tasks).then(function() {
+        runTasks().then(function() {
             if (tally.sheets) {
                 if (options.writeDest) {
                     var size = chalk.dim(maxmin(tally.sizeBefore, tally.sizeAfter));

From c2cbfe9e0fad8789339e46d807c11a927c1be47d Mon Sep 17 00:00:00 2001
From: Vitaliy Ribachenko <vit@ribachenko.com>
Date: Wed, 5 Dec 2018 08:08:58 +0200
Subject: [PATCH 2/2] Add tests for sequential option

---
 Gruntfile.js | 8 ++++++++
 test/test.js | 8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/Gruntfile.js b/Gruntfile.js
index 5850b18..dfefa1e 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -103,6 +103,14 @@ module.exports = function(grunt) {
                 },
                 src: 'test/fixtures/a.scss',
                 dest: 'tmp/noWriteDest.scss'
+            },
+            sequential: {
+                options: {
+                    syntax: require('postcss-scss'),
+                    sequential: true
+                },
+                src: ['test/fixtures/a.scss', 'test/fixtures/a.css'],
+                dest: 'tmp/sequential.css'
             }
         },
 
diff --git a/test/test.js b/test/test.js
index 32fcbb1..b64ac10 100644
--- a/test/test.js
+++ b/test/test.js
@@ -133,4 +133,12 @@ exports.gruntPostcss = {
         test.ok(!grunt.file.exists('tmp/noWriteDest.scss'));
         test.done();
     },
+
+    sequential: function(test) {
+        test.ok(grunt.file.exists('tmp/sequential.css'));
+        var actual = grunt.file.read('tmp/sequential.css');
+        var expected = grunt.file.read('test/fixtures/a.css');
+        test.strictEqual(actual, expected);
+        test.done();
+    },
 };