Hh rm mixins

[hhaensel]

Currently we have no possibility of including vue mixins.

This PR uses the existing rendering methods for ReactiveModels and makes it possible of including named apps as mixins.
The idea is to make it easier to develop reusable Plugins.

A demo is given in the doc string of the new macro @mixins.

using Stipple, Stipple.ReactiveTools
using StippleUI

@app GreetMixin begin
  @in name = "John Doe"
end

@mounted GreetMixin = "console.log('Just mounted the App including the GreetMixin')"

@methods GreetMixin :greet => "function() { console.log('Hi ' + this.name + '!') }"

@mixins [GreetMixin]

@app begin
  @mixin GreetMixin
  @in s = "Hi"
  @in i = 10
end

ui() = btn("Say Hello", @click("greet"))

@page("/", ui())

up(open_browser = true)

@essenciary @PGimenez I made this a draft PR to discuss whether this implementation is sufficient or how we could develop this further.

• Currently, I don't have a clear idea how to support pre- / postfixes that we support with the @mixin, we would need to define js_methods, etc with optional kwargs pre and post, I suppose.
• currently, it is necessary to add the mixins at two places. We could modify the @mixin macro to call @mixins. This will currently not work properly without supporting post and prefixes, at least, if the mixins are used like @mixin hh::MyMixin because that calls @mixin with a prefix.
• Currently the handlers are not ported

[hhaensel]

Example use case:

You have a multipage app and an SSO load script.
Then you can define all fields and scripts to manage your SSO sign-on for your sign-on-app and simply include it in all pages.

[hhaensel]

Update: embedding handlers without prefixes is easy an already included now

[hhaensel]

Demo App

# Test of `@mixins` from branch hh-rm-mixins (https://github.com/GenieFramework/Stipple.jl/pull/245)

using Stipple, Stipple.ReactiveTools
using StippleUI

@app GreetMixin begin
  @in name = "John Doe"

  @onchange name begin
    println("'name' changed to $(name)!")
  end

end greet_handlers

@mounted GreetMixin = "console.log('Just mounted the App including the GreetMixin')"

@methods GreetMixin :greet => "function() { console.log('Hi ' + this.name + '!') }"

@mixins [GreetMixin]

@app begin
  @mixin GreetMixin
  @in s = "Hi"
  @in i = 10

  @onchange i begin
    println("'i' changed to $(i)!")
  end
end

ui() = row(cell(class = "st-module", [
  cell(class = "q-my-md q-pa-md bg-green-3", "Name: {{name}}")
  cell(class = "q-my-md q-pa-md bg-green-4", "i: {{i}}")
  
  btn("client mixin 'greet'", @click("greet"), color = "red-3", nocaps = true)
  btn(class = "q-ml-md", "backend mixin '@onchange name'", @click("name = 'John ' + (name.endsWith('Doe') ? 'Dough' : 'Doe')"), color = "red-3", nocaps = true)
]))

@page("/", ui)

up(open_browser = true)

[hhaensel]

After having implemented handlers including prefix and postfix for the current @mixin approach, we can think about pushing this further ...
Currently no time but would be nice to have a discussion on this.