Monday, October 6, 2014

Simple Polymer Generators with Yeoman

I shaved 3 minutes off the Patterns in Polymer screencast that deals with the initial Polymer element generation in Dart. I still need to find another 3 minutes, but that is a good start. Good enough that I would to explore doing the same with JavaScript Polymer elements. Since I would like to stick with standard, maintained generators, this means Yeoman.

In all honesty, I have never used Yeoman. I tend to prefer writing initial applications / widgets by hand. I regard code that I maintain directly as too important to trust without hand-writing. If code is a starship, then I side with Sarris that a captain “know every bolt, every weld in his ship.” I might treat the inner workings of bolt creation and welding tools as abstractions that I can delve into later, but I will understand them well enough and know where they reside in my code.

That said, I don't hate code generation. Especially if they save me 3+ minutes in screencasts.

So I start by installing Yeoman:
$ npm install -g yo
/home/chris/local/node-v0.10.20/bin/yo -> /home/chris/local/node-v0.10.20/lib/node_modules/yo/cli.js

> yo@1.3.0 postinstall /home/chris/local/node-v0.10.20/lib/node_modules/yo
> node ./scripts/doctor

[Yeoman Doctor] Everything looks alright!

yo@1.3.0 /home/chris/local/node-v0.10.20/lib/node_modules/yo
├── ...
└── yeoman-generator@0.17.7 (...)
Next, I install the Polymer generator for Yeoman:
$ npm install -g generator-polymer
generator-polymer@0.5.1 /home/chris/local/node-v0.10.20/lib/node_modules/generator-polymer
With that, I am ready to run the generator in a new (temporary) project:
$ cd ~/tmp
$ mkdir x_pizza
$ cd !$
$ yo polymer
? Would you like to include core-elements? No
? Would you like to include paper-elements? No
? Would you like to use SASS/SCSS for element styles? No
   create .gitignore
   create .gitattributes
   create .bowerrc
   create bower.json
   create .jshintrc
   create .editorconfig
   create Gruntfile.js
   create package.json
   create app/404.html
   create app/favicon.ico
   create app/robots.txt
   create app/styles/main.css
   create app/scripts/app.js
   create app/.htaccess
   create app/elements/elements.html
   create app/elements/yo-list/yo-list.html
   create app/elements/yo-list/yo-list.css
   create app/elements/yo-greeting/yo-greeting.html
   create app/elements/yo-greeting/yo-greeting.css
   create app/index.html
   create app/test/index.html
   create app/test/tests.html
   create app/test/yo-greeting-basic.html
   create app/test/yo-list-basic.html
Yikes! That is a lot of infrastructure. I would rather focus on teaching Polymer than Polymer-on-Yeoman in these screencasts. The default page in app/index.html file and the sample Polymer element that it includes are nice demos, but I have the feeling that I may end up deleting a bunch of this for use in the screencast. On the other hand, it is nice that it creates a useful bower.json and runs bower.json. I will have to consider this.

The element generator is pretty clean however:
$ yo polymer:el x-pizza
? Would you like an external CSS file for this element? No
? Would you like to include an import in your elements.html file? No
   create app/elements/x-pizza/x-pizza.html
$ cat app/elements/x-pizza/x-pizza.html
<link rel="import" href="../../bower_components/polymer/polymer.html">
<polymer-element name="x-pizza" attributes="">
      :host {
        display: block;
    (function () {
      'use strict';
        // define element prototype here
I might quibble with the Polymer class being inline instead of in a separate script file, but that is close to what I want.

But in the end, I think the seed-element generator is closer to what I need for the screencasts. There is less infrastructure, but it still generates a smoke test page and a skeleton for the template:
$ cd ..    
$ rm -rf x_pizza 
$ mkdir x_pizza
$ cd !$
$ yo polymer:seed

    |       |    .--------------------------.
    |--(o)--|    | Out of the box I include |
   `---------´   |        the Polymer       |
    ( _´U`_ )    |       seed-element.      |
    /___A___\    '--------------------------'
     |  ~  |     
 ´   `  |° ´ Y ` 

? What is your GitHub username? eee-c
? What is your element's name: x-pizza
   create .gitignore
   create .gitattributes
   create .bowerrc
   create bower.json
   create .jshintrc
   create .editorconfig
   create x-pizza.css
   create x-pizza.html
   create index.html
   create demo.html
   create test/index.html
   create test/x-pizza-basic.html
   create test/tests.html
This also runs bower install, so I will be ready to start coding right away. The demo.html page that uses the generated <x-pizza> element is welcomingly brief. The generated element, however, is crazy long—it even includes a fireLasers() method.

So it does not seem that generating scaffold code in JavaScript is going to be as easy in JavaScript as in Dart. Hopefully I can work with it to keep the running time under 10 minutes. Time will tell.

Day #205

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