Switch up how we insantiate Bottleneck so rate limit can be configured

README.md

@@ -194,3 +194,4 @@ The plugin takes a single object as its only parameter. The following properties
 | `preserve`        | `boolean` | Whether or not to remove selectors from primary CSS document once they've been marked as critical. This should prevent duplication of selectors across critical and non-critical CSS. | `true` |
 | `minify`          | `boolean` | Minify output CSS?                          | `true` |
 | `ignoreSelectors` | `array`   | Array of selectors to globally exclude from critical CSS output | `[]` |
+| `fsWriteRate`   | `number`  | Minimum amount of time between file writes, in millisenconds. This is intended to prevent overlapping file writes for codebases with numerous calls to `@critical` | `250` |

lib/index.js

@@ -14,20 +14,22 @@ var _asyncToGenerator3 = _interopRequireDefault(_asyncToGenerator2);
  * @param {bool} dryRun Do a dry run?
  * @param {string} filePath Path to write file to.
  * @param {Object} result PostCSS root object.
+ * @param {number} fsWriteRate minimum time between file writes
  * @return {Promise} Resolves with writeCriticalFile or doDryRun function call.
  */
 let dryRunOrWriteFile = (() => {
-  var _ref = (0, _asyncToGenerator3.default)(function* (dryRun, filePath, result) {
+  var _ref = (0, _asyncToGenerator3.default)(function* (dryRun, filePath, result, fsWriteRate) {
     const css = result.css;
 
     if (dryRun) {
       doDryRun(css);
     } else {
-      yield limiter.schedule(writeCriticalFile, filePath, css);
+      // Write file at a maximum of once ever 250ms
+      yield createOrGetLimiter(fsWriteRate).schedule(writeCriticalFile, filePath, css);
     }
   });
 
-  return function dryRunOrWriteFile(_x, _x2, _x3) {
+  return function dryRunOrWriteFile(_x, _x2, _x3, _x4) {
     return _ref.apply(this, arguments);
   };
 })();
@@ -49,7 +51,6 @@ let dryRunOrWriteFile = (() => {
  */
 let writeCriticalFile = (() => {
   var _ref2 = (0, _asyncToGenerator3.default)(function* (filePath, css) {
-    console.log(`writeCriticalFile: ${filePath}`);
     try {
       yield _fsExtra2.default.outputFile(filePath, css, { flag: append ? 'a' : 'w' });
       append = true;
@@ -61,7 +62,7 @@ let writeCriticalFile = (() => {
     }
   });
 
-  return function writeCriticalFile(_x4, _x5) {
+  return function writeCriticalFile(_x5, _x6) {
     return _ref2.apply(this, arguments);
   };
 })();
@@ -106,14 +107,24 @@ function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { de
 let append = false;
 
 /**
- * Rate limiter for file writes
+ * Instance of Bottleneck for rate-limiting file writes
+ *
+ * @param {number} fsWriteRate minimum time between file writes
  */
 
 
-const limiter = new _bottleneck2.default({
-  maxConcurrent: 1,
-  minTime: 250
-});
+let limiter;
+
+function createOrGetLimiter(fsWriteRate) {
+  if (!limiter) {
+    limiter = new _bottleneck2.default({
+      maxConcurrent: 1,
+      minTime: fsWriteRate
+    });
+  }
+
+  return limiter;
+}
 
 /**
  * Clean the original root node passed to the plugin, removing custom atrules,
@@ -187,9 +198,11 @@ function doDryRun(css) {
     preserve: true,
     minify: true,
     dryRun: false,
-    ignoreSelectors: [':export', ':import']
+    ignoreSelectors: [],
+    fsWriteRate: 250
   }, filteredOptions);
   append = false;
+
   return (() => {
     var _ref3 = (0, _asyncToGenerator3.default)(function* (css) {
       const dryRun = args.dryRun,
@@ -212,6 +225,7 @@ function doDryRun(css) {
           const criticalCSS = _postcss2.default.root();
           const filePath = _path2.default.join(outputPath, outputFile);
           criticalOutput[outputFile].each(function (rule) {
+            // Check if we should remove this selector from output
             const shouldIgnore = rule.selector && args.ignoreSelectors.some(function (ignore) {
               return rule.selector.includes(ignore);
             });
@@ -222,7 +236,7 @@ function doDryRun(css) {
             return criticalCSS.append(rule.clone());
           });
           result = yield (0, _postcss2.default)(minify ? [_cssnano2.default] : []).process(criticalCSS, { from: undefined });
-          yield dryRunOrWriteFile(dryRun, filePath, result);
+          yield dryRunOrWriteFile(dryRun, filePath, result, args.fsWriteRate);
           clean(css, preserve);
         }
       } catch (err) {
@@ -243,7 +257,7 @@ function doDryRun(css) {
       return result;
     });
 
-    return function (_x6) {
+    return function (_x7) {
       return _ref3.apply(this, arguments);
     };
   })();

src/index.js

@@ -14,12 +14,26 @@ import { getCriticalRules } from './getCriticalRules'
 let append = false
 
 /**
- * Rate limiter for file writes
+ * Instance of Bottleneck for rate-limiting file writes
  */
-const limiter = new Bottleneck({
-  maxConcurrent: 1,
-  minTime: 250
-})
+let limiter
+
+/**
+ * Create or get a "singleton" instance of Bottleneck
+ *
+ * @param {number} fsWriteRate minimum time between file writes
+ * @return {Bottleneck} instnance of Bottleneck
+ */
+function createOrGetLimiter (fsWriteRate: number): Bottleneck {
+  if (!limiter) {
+    limiter = new Bottleneck({
+      maxConcurrent: 1,
+      minTime: fsWriteRate
+    })
+  }
+
+  return limiter
+}
 
 /**
  * Clean the original root node passed to the plugin, removing custom atrules,
@@ -95,19 +109,21 @@ function doDryRun (css: string) {
  * @param {bool} dryRun Do a dry run?
  * @param {string} filePath Path to write file to.
  * @param {Object} result PostCSS root object.
+ * @param {number} fsWriteRate minimum time between file writes
  * @return {Promise} Resolves with writeCriticalFile or doDryRun function call.
  */
 async function dryRunOrWriteFile (
   dryRun: boolean,
   filePath: string,
-  result: Object
+  result: Object,
+  fsWriteRate: number
 ): Promise<any> {
   const { css } = result
   if (dryRun) {
     doDryRun(css)
   } else {
     // Write file at a maximum of once ever 250ms
-    await limiter.schedule(
+    await createOrGetLimiter(fsWriteRate).schedule(
       writeCriticalFile,
       filePath,
       css
@@ -136,7 +152,6 @@ function hasNoOtherChildNodes (
  * @param {string} css CSS to write to file.
  */
 async function writeCriticalFile (filePath: string, css: string): Promise<any> {
-  console.log(`writeCriticalFile: ${filePath}`)
   try {
     await fs.outputFile(
       filePath,
@@ -173,9 +188,11 @@ function buildCritical (options: Object = {}): Function {
     minify: true,
     dryRun: false,
     ignoreSelectors: [],
+    fsWriteRate: 250,
     ...filteredOptions
   }
   append = false
+
   return async (css: Object): Object => {
     const { dryRun, preserve, minify, outputPath, outputDest } = args
     const criticalOutput = getCriticalRules(css, outputDest)
@@ -196,7 +213,7 @@ function buildCritical (options: Object = {}): Function {
       })
       result = await postcss(minify ? [cssnano] : [])
         .process(criticalCSS, { from: undefined })
-      await dryRunOrWriteFile(dryRun, filePath, result)
+      await dryRunOrWriteFile(dryRun, filePath, result, args.fsWriteRate)
       clean(css, preserve)
     }