Install: Use a cache folder for binary download

New order of operations
1. Look for existing binary in vendor folder
2. Create target vendor folder
3. Look to see if we’ve cached a copy in the configured or NPM cache
4. Download to current version’s /CACHE/node-sass/version/binding_file
5. Copy the cached download to the regular vendor directory
Closes #1566

lib/extensions.js

@@ -259,6 +259,17 @@ function getBinaryPath() {
 }
 
 /**
+ * Looks for the configured cache path. If none is found, fall back to the NPM
+ * cache folder
+ *
+ * @api public
+ */
+function getCachePath() {
+  return process.env.npm_config_sass_binary_cache ||
+         process.env.npm_config_cache;
+}
+
+/**
  * Does the supplied binary path exist
  *
  * @param {String} binaryPath
@@ -286,6 +297,7 @@ module.exports.hasBinary = hasBinary;
 module.exports.getBinaryUrl = getBinaryUrl;
 module.exports.getBinaryName = getBinaryName;
 module.exports.getBinaryPath = getBinaryPath;
+module.exports.getCachePath = getCachePath;
 module.exports.getVersionInfo = getVersionInfo;
 module.exports.getHumanEnvironment = getHumanEnvironment;
 module.exports.getInstalledBinaries = getInstalledBinaries;

scripts/install.js

@@ -131,37 +131,50 @@ function getProxy() {
  */
 
 function checkAndDownloadBinary() {
-  if (sass.hasBinary(sass.getBinaryPath())) {
+  if (process.env.SKIP_SASS_BINARY_DOWNLOAD_FOR_CI) {
+    console.log('Skipping downloading binaries on CI builds');
     return;
   }
+  var binaryPath = sass.getBinaryPath();
 
-  mkdir(path.dirname(sass.getBinaryPath()), function(err) {
+  if (sass.hasBinary(binaryPath)) {
+    return;
+  }
+
+  mkdir(path.dirname(binaryPath), function(err) {
     if (err) {
       console.error(err);
       return;
     }
 
-    download(sass.getBinaryUrl(), sass.getBinaryPath(), function(err) {
-      if (err) {
-        console.error(err);
-        return;
-      }
-
-      console.log('Binary downloaded and installed at', sass.getBinaryPath());
-    });
+    var cachePath = path.join(sass.getCachePath(), pkg.name, pkg.version);
+    var cacheBinary = path.join(cachePath, sass.getBinaryName());
+    if (fs.existsSync(cacheBinary)) {
+      console.log('Found existing binary in ' + cacheBinary);
+      fs.createReadStream(cacheBinary).pipe(fs.createWriteStream(binaryPath));
+    } else {
+      // In case the cache path doesn't exist
+      mkdir(cachePath, function(err) {
+        if (err) {
+          console.error(err);
+          return;
+        }
+
+        download(sass.getBinaryUrl(), cacheBinary, function(err) {
+          if (err) {
+            console.error(err);
+            return;
+          }
+
+          console.log('Binary downloaded to ' + cacheBinary);
+          fs.createReadStream(cacheBinary).pipe(fs.createWriteStream(binaryPath));
+        });
+      });
+    }
   });
 }
 
 /**
- * Skip if CI
- */
-
-if (process.env.SKIP_SASS_BINARY_DOWNLOAD_FOR_CI) {
-  console.log('Skipping downloading binaries on CI builds');
-  return;
-}
-
-/**
  * If binary does not exist, download it
  */
 

test/runtime.js

@@ -134,6 +134,29 @@ describe('runtime parameters', function() {
     });
 
   });
+
+  describe('Sass Binary Cache', function() {
+    var npmCacheDir;
+    before(function() {
+      npmCacheDir = process.env.npm_config_cache;
+    });
+
+    beforeEach(function() {
+      delete process.env.npm_config_sass_binary_cache;
+    });
+
+    it('npm config variable', function() {
+      var overridenCachePath = '/foo/bar/';
+      process.env.npm_config_sass_binary_cache = overridenCachePath;
+      var sass = require(extensionsPath);
+      assert.equal(sass.getCachePath(), overridenCachePath);
+    });
+
+    it('With no value, falls back to NPM cache', function() {
+      var sass = require(extensionsPath);
+      assert.equal(sass.getCachePath(), npmCacheDir);
+    });
+  });
 });
 
 // describe('library detection', function() {