Fix 'unreadable file error' for node-sass

node_sass_patch.diff

Original from: https://github.com/sass/node-sass/pull/2386
               https://github.com/marcosbozzani/node-sass/commit/266861b.diff
Modified to include exponential backoff
--- render.js.bak	2018-07-28 22:33:12.784523700 +0800
+++ render.js	2018-07-29 11:42:15.442878400 +0800
@@ -42,11 +42,13 @@
     renderOptions.file = options.src;
   }
 
+  var retries = 0;
   var sourceMap = options.sourceMap;
   var destination = options.dest;
   var stdin = options.stdin;
 
   var success = function(result) {
+    retries = 0;
     var todo = 1;
     var done = function() {
       if (--todo <= 0) {
@@ -105,7 +107,29 @@
   };
 
   var error = function(error) {
-    emitter.emit('error', chalk.red(JSON.stringify(error, null, 2)));
+    if (isFileUnreadable(error) && retries < 4) {
+      retries++;
+      setTimeout(() => sass.render(renderOptions, renderCallback), Math.pow(retries, 5));
+    }
+    else {
+      emitter.emit('error', chalk.red(JSON.stringify(error, null, 2)));
+    }
+  };
+
+  var isFileUnreadable = function(error) {
+    var unreadable = typeof error.message === 'string' &&
+    (
+        error.message.startsWith('File to read not found or unreadable: ') ||
+        error.message.startsWith('File to import not found or unreadable: ')
+    );
+
+    return unreadable;
+    // if (unreadable) {
+    //   var file = error.message.split('not found or unreadable: ')[1].trim();
+    //   return fs.existsSync(file);
+    // }
+
+    // return false;
   };
 
   var renderCallback = function(err, result) {