Annotation to minify HTML and JSON Strings

[WhiteTrashLord]

Would it be possible to add an annotation which tells the GWT compiler to minify a Java String before the compilation to Javascript starts?
This might be very useful for HTML and JSON Strings.

[jnehlmeier]

What is the concrete use case?

To me it sounds like it is something your build tool can already do if you save the HTML / JSON strings as files and call some minify tool before calling GWT compiler. With an annotation based solution the string would need to have a valid structure which in turn means it is likely already pretty static in your code base. At most you concat static strings together right now, right?. In that case a file on disk could contain placeholders so you can replace it at runtime as needed. A lite templating mechanism.

To get access to the files in GWT you can use ClientBundle + TextResource or ExternalTextResource (text will be bundled with your JS or downloaded as needed).

[niloc132]

Can you elaborate what you mean by minify exactly? For example, rewriting string keys in the JSON to be shorter, etc?

Where would the annotation go?

What kind of savings are you hoping for? If the "minification" is just removing indentation, odds are very high that just gzipping static resources like your compiled JS file would have mostly the same effect as what you're seeking.

If what you are looking for is simple enough that you can express it with just calls on string literals - " mydata ".trim() or "...".replaceAll(" ", " ") should already be handled by the compiler as a rewrite that it can do while optimizing towards JS. This isn't always perfect, but #10255 is intended to improve it. Then, you can write your own tests for your code, and not have the compiler recognize "this is JSON, and here are my app's specific rules on how the data will work", so much as "here is some Java code you can optimize".

Jens's solution is a great one too, allowing you to implement exactly what you expect, and test it without needing to parse the inside of the optimized JS output.

[WhiteTrashLord]

Here is an example:

   @MinifyHTML
static String drinkshtml = """			
		<div id="drinks">
		    <ol>
		          <li>Black coffee</li>
		          <li>Green tea</li>
		          <li>Soy milk</li>
		     </ol>
		</div>
		""";

In Javascript the String would be minified to: <div id=drinks><ol><li>Black coffee</li><li>Green tea</li><li>Soy milk</li></ol></div>

Simple functions like replaceAll cannot be used in this case. I already have a custom template generator. But maybe with an annotation like this my process can be simplified. I don't want to use any outdated GWT classes. I want to use 100% elemental2 in all my new projects.

[niloc132]

If you're interested in writing an annotation processor, this shouldn't be too bad - its pretty close to how SafeHtmlTemplates work already (note, the resulting SafeHtml just exposes a String, so no existing gwt widget/dom classes required). Whether it is your own code or safehtml, it would look a little like this:

interface MyDrinksTemplate {

  @Minify("""
		<div id="drinks">
		    <ol>
		          <li>Black coffee</li>
		          <li>Green tea</li>
		          <li>Soy milk</li>
		     </ol>
		</div>
		""") 
  // or @Template(...) in SafeHtmlTemplates, which would also have return type below of SafeHtml
  String render();
}

Then you just generate the new type, applying any formatting you want, and call the new function:

MyDrinksTemplate template = new MyDrinksTemplate_Impl();
display(template.render());

Could also return elemental2.dom.HTMLElement or something too, since you own that code now. I have a "alpha" implementation of a react/angular/vue-style tool that lets you express templates like the above, and then attach a viewmodel, and at compile time the bindings and dom creation are worked out, but I haven't had the time/demand to put enough polish on it to release - but the idea is definitely sound.

[niloc132]

Closing - we can always reopen if you have other thoughts/questions. Consider joining the gitter channel at https://matrix.to/#/#gwtproject_gwt:gitter.im if you want to discuss in realtime, or the posting something to one of the mailing lists (https://groups.google.com/g/google-web-toolkit or https://groups.google.com/g/google-web-toolkit-contributors).