Merge pull request #3 from izaakschroeder/master

Support for error handling and promises

README.md

@@ -36,51 +36,40 @@ var MongoClient = require('mongodb').MongoClient;
 /*
   Get data via JSON file, keyed on filename.
 */
-var getJsonData = function(file, cb) {
-  var jsonPath = './examples/' + path.basename(file.path) + '.json';
-  cb(require(jsonPath));
-};
-
 gulp.task('json-test', function() {
   return gulp.src('./examples/test1.html')
-    .pipe(data(getJsonData))
+    .pipe(data(function(file) {
+      return require('./examples/' + path.basename(file.path) + '.json');
+    }))
     .pipe(swig())
     .pipe(gulp.dest('build'));
 });
 
-var getFrontMatter = function(file, cb) {
-  var content = fm(String(file.contents));
-  file.contents = new Buffer(content.body);
-  cb(content.attributes);
-};
-
 /*
   Get data via front matter
 */
 gulp.task('fm-test', function() {
   return gulp.src('./examples/test2.html')
-    .pipe(data(getFrontMatter))
+    .pipe(data(function(file) {
+      var content = fm(String(file.contents));
+      file.contents = new Buffer(content.body);
+      return content.attributes;
+    }))
     .pipe(swig())
     .pipe(gulp.dest('build'));
 });
 
 /*
   Get data via database, keyed on filename.
 */
-var getMongoData = function(file, cb) {
-  MongoClient.connect('mongodb://127.0.0.1:27017/gulp-data-test', function(err, db) {
-    if(err) throw err;
-    var collection = db.collection('file-data-test');
-    collection.findOne({filename: path.basename(file.path)}, function(err, doc) {
-      db.close();
-      cb(doc);
-    });
-  });
-};
-
 gulp.task('db-test', function() {
   return gulp.src('./examples/test3.html')
-    .pipe(data(getMongoData))
+    .pipe(data(function(file, cb) {
+      MongoClient.connect('mongodb://127.0.0.1:27017/gulp-data-test', function(err, db) {
+        if(err) return cb(err);
+        cb(undefined, db.collection('file-data-test').findOne({filename: path.basename(file.path)}));
+      });
+    }))
     .pipe(swig())
     .pipe(gulp.dest('build'));
 });
@@ -92,10 +81,52 @@ gulp.task('db-test', function() {
 ### data(dataFunction)
 
 #### dataFunction
-Type: `Function`  
+Type: `Function`
 
 Define a function that returns a data object via a callback function. Could return JSON from a file, or an object returned from a database.
 
+You can return the data object:
+```javascript
+data(function(file) {
+  return { 'foo': file.path }
+})
+```
+
+You can return a promise:
+```javascript
+data(function(file) {
+  return promise;
+})
+```
+
+You can feed a result object through the callback:
+```javascript
+data(function(file, callback) {
+  return callback(undefined, { 'foo': 'bar' });
+})
+```
+
+You can feed a promise object through the callback:
+```javascript
+data(function(file, callback) {
+  return callback(undefined, promise);
+})
+```
+
+You can throw an error:
+```javascript
+data(function(file) {
+  throw new Error('my-error');
+})
+```
+
+You can raise an error via the callback:
+```javascript
+data(function(file, callback) {
+  return callback('error');
+})
+```
+
 ## Note to gulp plugin authors
 
 If your plugin needs a data object, one that normally gets passed in via your options parameter, I'm asking if you could please update the plugin to accept data from the ```file.data``` property. Here's how you can do it:

index.js

@@ -14,6 +14,27 @@ module.exports = function(data) {
 
   function gulpData(file, enc, callback) {
     /*jshint validthis:true*/
+    var self = this, called = false;
+
+    function handle(err, result){
+      // extra guard in case
+      if (called) return;
+      called = true;
+      if (err) {
+        self.emit("error", new gutil.PluginError("gulp-data", { message: err }));
+        return callback();
+      }
+      file.data = result;
+      self.push(file);
+      callback();
+    }
+
+    function local(data) {
+      if (data && typeof data.then === 'function')
+        data.then(function(data){ return handle(undefined, data) }, function(err) { return handle(err); });
+      else
+        handle(undefined, data);
+    }
 
     // Do nothing if no contents
     if (file.isNull()) {
@@ -28,21 +49,23 @@ module.exports = function(data) {
       // https://github.com/dominictarr/event-stream
 
       // accepting streams is optional
-      this.emit("error",
-        new gutil.PluginError("gulp-data", "Stream content is not supported"));
+      this.emit("error", new gutil.PluginError("gulp-data", "Stream content is not supported"));
       return callback();
     }
 
     // check if file.contents is a `Buffer`
     if (file.isBuffer()) {
-      var self = this;
-      if (typeof data === 'function') {
-        data(file, function(result){
-          file.data = result;
-          self.push(file);
-          callback();
-        });
-      }
+      var res = null;
+      if (typeof data === 'function')
+          try {
+            res = data(file, handle);
+            if (data.length <= 1)
+              return local(res)
+          } catch(e) {
+            return handle(e);
+          }
+      else
+        local(data);
     }
   }
 

package.json

@@ -1,7 +1,7 @@
 {
   "name": "gulp-data",
-  "version": "0.1.0",
-  "description": "Generate a data object from a variety of sources: json, front-matter, database, anything... and set it to the file object for other plugins to consume.",
+  "version": "1.0.1",
+  "description": "Generate a data object from a variety of sources: json, front-matter, databases, promises, anything... and set it to the file object for other plugins to consume.",
   "keywords": [
     "gulpplugin", "data", "json", "gulp"
   ],
@@ -10,6 +10,11 @@
     "email": "colyn.brown@gmail.com",
     "url": "https://github.com/colynb"
   },
+  "contributors": [{
+    "name": "Izaak Schroeder",
+    "email": "izaak.schroeder@gmail.com",
+    "url": "http://www.github.com/izaakschroeder"
+  }],
   "repository": "colynb/gulp-data",
   "scripts": {
     "test": "istanbul test _mocha --report html -- test/*.js --reporter spec"
@@ -24,7 +29,8 @@
     "mocha-lcov-reporter": "*",
     "istanbul": "*",
     "event-stream": "*",
-    "should": "~2.1.0"
+    "should": "~2.1.0",
+    "q": "~1.0.1"
   },
   "engines": {
     "node": ">=0.8.0",