Third design iteration

[jonmmease]

This PR contains another round of updates, cleanup, and refactoring.

Highlights:

Plugin

Introduces a dash app plugin that customizes the behavior of app.callback, rather than requiring the use of dx.callback. (Closes #4)

import dash
import dash_express as dx
app = dash.Dash(__name__, plugins=[dx.Plugin()])

Compatibility

Full backward compatibility with Dash 1. The new Dash Express features are only available when providing @app.callback with the input/state/output keyword arguments, but regular dependency objects are now accepted as positional arguments again.

Remove ComponentProps

Removes the component.props[...] syntax and the ComponentProps class. Instead, a new props argument is added to dx.arg. So now, to customize the component properties you do

dx.arg(dcc.DatePickerRange(), props=("start_date", "end_date"), ...)

instead of

dx.arg(dcc.DatePickerRange().props[("start_date", "end_date")], ...)

It avoids introducing an additional class, and it provides a place (arg) to document that the default value is "value". This is a proposed resolution of #6.

Default argument kind

The default value of kind in dx.arg is now determined by whether the value is passed in the input or state keyword argument. This argument can be overridden by explicitly providing a value to the dx.arg constructor. This makes it possible to define the "manual" workflow more easily.

Instead of:

@app.callback(
    input=dict(
        fun=dx.arg(["sin", "cos", "exp"], label="Function", kind="state"),
        figure_title=dx.arg("Initial Title", label="Figure Title", kind="state"),
        phase=dx.arg((1, 10), label="Phase", kind="state"),
        amplitude=dx.arg((1, 10), label="Amplitude", kind="state"),
        n_clicks=dx.arg(html.Button("Update"), props="n_clicks")
    ),
)

All of the components specifications can be passed to the state keyword argument, and the button specified as kind=input so that it is treated as input.

@app.callback(
    state=dict(
        fun=dx.arg(["sin", "cos", "exp"], label="Function"),
        figure_title=dx.arg("Initial Title", label="Figure Title"),
        phase=dx.arg((1, 10), label="Phase"),
        amplitude=dx.arg((1, 10), label="Amplitude"),
        n_clicks=dx.arg(html.Button("Update"), props="n_clicks", kind="input")
    ),
)

Documentation and Demos

The DOCUMENTATION.md and associated demos have been updated with these changes