Add grunt.log.warn method

gruntjs/gruntjs-tests.ts

@@ -73,3 +73,46 @@ exports = (grunt: IGrunt) => {
     fileMaps[0].src.length;
     fileMaps[0].dest;
 };
+
+// Official grunt task template from 
+// https://github.com/gruntjs/grunt-init-gruntplugin/blob/master/root/tasks/name.js
+exports.exports = function(grunt: IGrunt) {
+
+    // Please see the Grunt documentation for more information regarding task
+    // creation: http://gruntjs.com/creating-tasks
+
+    grunt.registerMultiTask('taskName', 'task description', function() {
+        // Merge task-specific and/or target-specific options with these defaults.
+        var options = this.options({
+            punctuation: '.',
+            separator: ', '
+        });
+
+        // Iterate over all specified file groups.
+        this.files.forEach(function(f) {
+            // Concat specified files.
+            var src = f.src.filter(function(filepath) {
+                // Warn on and remove invalid source files (if nonull was set).
+                if (!grunt.file.exists(filepath)) {
+                    grunt.log.warn('Source file "' + filepath + '" not found.');
+                    return false;
+                } else {
+                    return true;
+                }
+            }).map(function(filepath) {
+                // Read file source.
+                return grunt.file.read(filepath);
+            }).join(grunt.util.normalizelf(options.separator));
+
+            // Handle options.
+            src += options.punctuation;
+
+            // Write the destination file.
+            grunt.file.write(f.dest, src);
+
+            // Print a success message.
+            grunt.log.writeln('File "' + f.dest + '" created.');
+        });
+    });
+
+};

gruntjs/gruntjs.d.ts

@@ -690,6 +690,11 @@ declare module grunt {
              * Log a list of obj properties (good for debugging flags).
              */
             writeflags(obj: any): T
+
+            /**
+             * Log an warning with grunt.log.warn
+             */
+            warn(msg: string): T
         }
 
         /**