support kwargs in @page macro

[hhaensel]

Currently different methods of the @page macro are distinguishable only by the number of arguments, requiring the argument order url, view, layout, model, context.
With the new macro tool expressions_to_args() we can support a kwarg-like macro call, e.g.

model = @init
@page("/", ui, model = model)

for global models without the requirement to specify a layout.

EDIT: Note that the ;-Syntax with auto duplication for kwargs is not supported in macros

[hhaensel]

Still thinking how we could support passing of more arguments to the init function ...

[hhaensel]

Now we can do:

@init(debounce = 10)

In order to change the settings after they have been already set, it is important to clear the cached route and DEPS. For this I introduced clear_cache() and @clear_cache

@clear_cache
@init(debounce = 12)

[hhaensel]

Before we think about merging, I'm going to support semicolon parameter syntax

[hhaensel]

Well, it's done. Needed to find out that macros only catch parameter syntax consistently when there is no positional argument in the definition.
Look at this:

macro f(x, expressions...)
    @show x expressions
    return nothing
end

@f(a, b="b"; c=c)
# x = :($(Expr(:parameters, :($(Expr(:kw, :c, :c))))))
# expressions = (:a, :(b = "b"))

[essenciary]

Interesting, I've never attempted this. With functions the keyword args are collected in the named tuple.

julia> f(args...; kwargs...) = print(args, kwargs)
f (generic function with 1 method)

julia> f(2, a=:a; b=3)
(2,)Base.Pairs{Symbol, Any, Tuple{Symbol, Symbol}, NamedTuple{(:a, :b), Tuple{Symbol, Int64}}}(:a => :a, :b => 3)

Because it's passed before the ;, the a=:a argument is passed as one entity, a named tuple.

[hhaensel]

Yeah, the functions do aggregate args and kwargs, I've used that a thousand times.
I even investigated macro syntax when I wrote my bits of the onchange parser. But I didn't realise that distribution to args goes wrong.
I'll ask this on discourse...

EDIT:

• corrected typo
• seems to be known, see discourse

[PGimenez]

One thought. Should we enforce strict ordering so that kw arguments? (if it can be done) Now you can do something like

@page("/model2", model = Model, ui )

which works since the macro rearranges the parameters inside. This may suggest that order is not important, but if one were to try

@page(ui,  model = Model, "/model2" )

it wouldn't work.

Other than this, I like the changes and it's very useful for when you want to use multiple models without specifying a layout.

[hhaensel]

I think it is known from functions that the order of positional arguments is important while the oder of kwargs is not.
That's exactly the behaviour I copied.