Allow to specify an objectToExportTo for goog.exportSymbol

This allows users to build ol3 without anything exposed in the
global namespace. This can e.g. be useful for creating an ol3
AMD module, by simply using a build configuration with
"define('ol',function(){var o={};%output%return o.ol;});" as
"output_wrapper".

tasks/generate-exports.js

@@ -19,7 +19,7 @@ var build = path.join(__dirname, '..', 'build');
  * @param {function(Error, Array.<string>)} callback Called with the list of
  *     patterns.
  */
-function getPatterns(configPath, callback) {
+function getConfig(configPath, callback) {
   if (configPath) {
     fs.readFile(configPath, function(err, data) {
       if (err) {
@@ -38,11 +38,17 @@ function getPatterns(configPath, callback) {
         callback(new Error('Expected an exports array, got: ' + patterns));
         return;
       }
-      callback(null, patterns);
+      var namespace = obj.namespace;
+      if (namespace && typeof namespace !== 'string') {
+        callback(new Error('Expected an namespace string, got: ' +
+            namespace));
+        return;
+      }
+      callback(null, patterns, namespace);
     });
   } else {
     process.nextTick(function() {
-      callback(null, ['*']);
+      callback(null, ['*'], undefined);
     });
   }
 }
@@ -117,12 +123,15 @@ function filterSymbols(patterns, symbols, callback) {
 /**
  * Generate goog code to export a named symbol.
  * @param {string} name Symbol name.
+ * @param {string|undefined} namespace Target object for exported
+ *     symbols.
  * @return {string} Export code.
  */
-function formatSymbolExport(name) {
+function formatSymbolExport(name, namespace) {
   return 'goog.exportSymbol(\n' +
       '    \'' + name + '\',\n' +
-      '    ' + name + ');\n';
+      '    ' + name +
+      (namespace ? ',\n    ' + namespace : '') +');\n';
 }
 
 
@@ -145,9 +154,10 @@ function formatPropertyExport(name) {
 /**
  * Generate export code given a list symbol names.
  * @param {Array.<Object>} symbols List of symbols.
+ * @param {string|undefined} namespace Target object for exported symbols.
  * @return {string} Export code.
  */
-function generateExports(symbols) {
+function generateExports(symbols, namespace) {
   var blocks = [];
   var requires = {};
   symbols.forEach(function(symbol) {
@@ -158,7 +168,7 @@ function generateExports(symbols) {
     if (name.indexOf('#') > 0) {
       blocks.push(formatPropertyExport(name));
     } else {
-      blocks.push(formatSymbolExport(name));
+      blocks.push(formatSymbolExport(name, namespace));
     }
   });
   blocks.unshift('\n');
@@ -173,17 +183,18 @@ function generateExports(symbols) {
  * Generate the exports code.
  *
  * @param {Array.<string>} patterns List of symbol names or patterns.
+ * @param {string|undefined} namespace Target object for exported symbols.
  * @param {function(Error, string)} callback Called with the exports code or any
  *     error generating it.
  */
-function main(patterns, callback) {
+function main(patterns, namespace, callback) {
   async.waterfall([
     getSymbols.bind(null, patterns),
     filterSymbols,
     function(symbols, done) {
       var code, err;
       try {
-        code = generateExports(symbols);
+        code = generateExports(symbols, namespace);
       } catch (e) {
         err = e;
       }
@@ -212,7 +223,7 @@ if (require.main === module) {
   }).parse();
 
   async.waterfall([
-    getPatterns.bind(null, options.config),
+    getConfig.bind(null, options.config),
     main,
     fse.outputFile.bind(fse, options.output)
   ], function(err) {