- Switched from passing on a stream to passing on a string.

- Used database instead of filesystem in the cache example.
- Moved the fallback handler to a method one scope out.

Author: martinheidegger

index.js

@@ -201,10 +201,7 @@ Deps.prototype.resolve = function (id, parent, cb) {
 Deps.prototype.readFile = function (file, id, pkg) {
     var self = this;
     if (xhas(this.fileCache, file)) {
-        var tr = through();
-        tr.push(this.fileCache[file]);
-        tr.push(null);
-        return tr;
+        return toStream(this.fileCache[file]);
     }
     var rs = fs.createReadStream(file, {
         encoding: 'utf8'
@@ -381,8 +378,22 @@ Deps.prototype.walk = function (id, parent, cb) {
         var c = self.cache && self.cache[file];
         if (c) return fromDeps(file, c.source, c.package, fakePath, Object.keys(c.deps));
 
-        self.persistentCache(file, id, pkg, function fallback (stream, cb) {
-            (stream || self.readFile(file, id, pkg))
+        self.persistentCache(file, id, pkg, persistentCacheFallback, function (err, c) {
+            if (err) {
+                self.emit('error', err);
+                return;
+            }
+            fromDeps(file, c.source, c.package, fakePath, Object.keys(c.deps));
+        });
+
+        function persistentCacheFallback (dataAsString, cb) {
+            var stream
+            if (dataAsString) {
+                stream = toStream(dataAsString)
+            } else {
+                stream = self.readFile(file, id, pkg)
+            }
+            stream
                 .pipe(self.getTransforms(fakePath || file, pkg, {
                     builtin: builtin,
                     inNodeModules: parent.inNodeModules
@@ -401,13 +412,7 @@ Deps.prototype.walk = function (id, parent, cb) {
                         });
                     }
                 }));
-        }, function (err, c) {
-            if (err) {
-                self.emit('error', err);
-                return;
-            }
-            fromDeps(file, c.source, c.package, fakePath, Object.keys(c.deps));
-        });
+        }
     });
 
     function getDeps (file, src) {
@@ -577,6 +582,13 @@ function xhas (obj) {
     return true;
 }
 
+function toStream (dataAsString) {
+    var tr = through();
+    tr.push(dataAsString);
+    tr.push(null);
+    return tr;
+}
+
 function has (obj, key) {
     return obj && Object.prototype.hasOwnProperty.call(obj, key);
 }

readme.markdown

@@ -106,23 +106,35 @@ from disk.
         if (hasError()) {
             return cb(error) // Pass any error to the callback
         }
-        if (isInCache()) {
+
+        var fileData = fs.readFileSync(file)
+        var key = keyFromFile(file, fileData)
+
+        if (db.has(key)) {
             return cb(null, {
-                source: fs.readFileSync(file, 'utf8'), // String of the fully processed file
+                source: db.get(key).toString(),
                 package: pkg, // The package for housekeeping
                 deps: {
                     'id':  // id that is used to reference a required file
                     'file' // file path to the required file
                 }
             })
         }
-        // optional (can be null) stream that provides the data from
-        // the hard disk, can be provided in case the file data is used
-        // to evaluate the cache identifier
-        stream = fs.createReadStream(file)
-
-        // fallback to the default reading
-        fallback(stream, cb)
+        //
+        // The fallback will process the file in case the file is not
+        // in cache.
+        //
+        // Note that if your implementation doesn't need the file data
+        // then you can pass `null` instead of the source and the fallback will
+        // fetch the data by itself.
+        //
+        fallback(fileData, function (error, cacheableEntry) {
+            if (error) {
+                return cb(error)
+            }
+            db.addToCache(key, cacheableEntry)
+            cb(null, cacheableEntry)
+        })
     }
     ```
 

test/cache_persistent.js

@@ -59,7 +59,7 @@ test('allow passing of a different stream', function (t) {
     t.plan(1);
     var p = parser({
         persistentCache: function (file, id, pkg, fallback, cb) {
-            fallback(fs.createReadStream(files.bar), cb)
+            fallback(fs.readFileSync(files.bar, 'utf8'), cb)
         }
     });
     p.end({ id: 'foo', file: files.foo, entry: false });