Improve CLI parsing error

bin/mustache

@@ -46,10 +46,23 @@ function readView(cb) {
   var view = isStdin(viewArg) ? process.openStdin() : fs.createReadStream(viewArg);
 
   streamToStr(view, function(str) {
-    cb(JSON.parse(str));
+    cb(parseView(str));
   });
 }
 
+function parseView(str) {
+  try {
+    return JSON.parse(str);
+  } catch (ex) {
+    console.error(
+      'Shooot, could not parse view as JSON.\n'+
+      'Tips: functions are not valid JSON and keys / values must be surround with double quotes.\n\n'+
+      ex.stack);
+
+    process.exit(1);
+  }
+}
+
 function readTemplate(cb) {
   var template = fs.createReadStream(templateArg);
   streamToStr(template, cb);

test/cli-test.js

@@ -28,6 +28,13 @@ describe('Mustache CLI', function () {
     });
   });
 
+  it('writes hints about JSON parsing errors when given invalid JSON', function(done) {
+    exec('echo {name:"lebron"} | bin/mustache - test/_files/cli.mustache', function(err, stdout, stderr) {
+      assert.notEqual(stderr.indexOf('Shooot, could not parse view as JSON'), -1);
+      done();
+    });
+  });
+
   it('writes module version into stdout when runned with --version', function(done){
     exec('bin/mustache --version', function(err, stdout, stderr) {
       assert.notEqual(stdout.indexOf(moduleVersion), -1);