Read only option

README.md

@@ -54,6 +54,7 @@ module.exports = {
 | **`cacheIdentifier`** |                    `{String}`                    | `cache-loader:{version} {process.env.NODE_ENV}` | Provide an invalidation identifier which is used to generate the hashes. You can use it for extra dependencies of loaders (used for default read/write implementation) |
 |      **`write`**      | `{Function(cacheKey, data, callback) -> {void}}` |                   `undefined`                   | Allows you to override default write cache data to file (e.g. Redis, memcached)                                                                                        |
 |      **`read`**       |    `{Function(cacheKey, callback) -> {void}}`    |                   `undefined`                   | Allows you to override default read cache data from file                                                                                                               |
+|    **`readOnly`**     |                    `{Boolean}`                   |                   `false`                       | Allows you to override default value and make the cache read only (useful for some environments where you don't want the cache to be updated, only read from it)       |
 
 ## Examples
 

src/index.js

@@ -23,6 +23,7 @@ const defaults = {
   cacheIdentifier: `cache-loader:${pkg.version} ${env}`,
   cacheKey,
   read,
+  readOnly: false,
   write,
 };
 
@@ -46,10 +47,16 @@ function pathWithCacheContext(cacheContext, originalPath) {
 
 function loader(...args) {
   const options = Object.assign({}, defaults, getOptions(this));
-
   validateOptions(schema, options, 'Cache Loader');
 
-  const { write: writeFn } = options;
+  const { readOnly, write: writeFn } = options;
+
+  // In case we are under a readOnly mode on cache-loader
+  // we don't want to write or update any cache file
+  if (readOnly) {
+    this.callback(null, ...args);
+    return;
+  }
 
   const callback = this.async();
   const { data } = this;
@@ -124,7 +131,12 @@ function pitch(remainingRequest, prevRequest, dataInput) {
 
   validateOptions(schema, options, 'Cache Loader (Pitch)');
 
-  const { read: readFn, cacheContext, cacheKey: cacheKeyFn } = options;
+  const {
+    read: readFn,
+    readOnly,
+    cacheContext,
+    cacheKey: cacheKeyFn,
+  } = options;
 
   const callback = this.async();
   const data = dataInput;
@@ -150,6 +162,15 @@ function pitch(remainingRequest, prevRequest, dataInput) {
             eachCallback(statErr);
             return;
           }
+
+          // When we are under a readOnly config on cache-loader
+          // we don't want to emit any other error than a
+          // file stat error
+          if (readOnly) {
+            eachCallback();
+            return;
+          }
+
           if (stats.mtime.getTime() !== dep.mtime) {
             eachCallback(true);
             return;

src/options.json

@@ -16,6 +16,9 @@
     "read": {
       "instanceof": "Function"
     },
+    "readOnly": {
+      "type": "boolean"
+    },
     "write": {
       "instanceof": "Function"
     }