Dash 1.0

Dash has been in active development for more than two years. In that time
we’ve seen it evolve into a robust framework with a worldwide community of
users. As we continued building Dash, talking and working with Dash users,
we developed new features that obsoleted old ones, discovered which
settings are awkward or confusing to new users, and overall accumulated a
lot of ideas for how to improve the experience of building Dash apps.

A lot of these ideas have already been built into Dash. Sometimes they
require changes that break backward compatibility. When these changes were
small enough we added them anyway - we’re still on major version 0 so
SemVer allows breaking changes after all - but
others we still held back because we expected them to impact too many
users.

Dash version 1.0, in addition to various new features and upgrades we
discuss elsewhere, collects those breaking changes all in one release.
With it we are affirming the maturity and stability of the Dash and
Dash component API. After making this migration, which we expect will
impact a sizable fraction of Dash users in one way or another, Dash will
not introduce any breaking changes unless and until we bump the major
version again. That commitment includes the public API of the whole Dash
“core”: dash, dash_core_components, dash_html_components,
and dash_table.

Here are the changes Dash developers need to know about to transition apps
from v0.43 (the last release in the v0.x series) to v1.0.

dash

serve_locally: default True and new kwarg

Previously Dash would try to serve JavaScript and CSS files from public
CDNs by default, and to disable this you needed to set:

app.scripts.config.serve_locally = True
app.css.config.serve_locally = True

Now that’s the default, and that syntax can still be used to disable it for
each asset class, but if you want to use CDNs for both you can just do:

app = dash.Dash(serve_locally=False)

Note that using app.scripts.append_script to load external js scripts
won’t work while serve_locally=True. Please use the external_scripts argument
in your call to dash.Dash instead, as outlined in the external resources section.

Removed undo/redo buttons

The undo & redo buttons in the corner of every app are removed by default,
but if you want to re-enable them, set:

app = dash.Dash(show_undo_redo=True)

Removed static_folder

This old dash.Dash kwarg has been superseded by the much more powerful
assets_folder. If you want the old behavior, use a custom server:

app = dash.Dash(server=Flask(static_folder='my_folder'))

Removed components_cache_max_age

All assets are served with cache-busting query strings in their URLs,
so this is unnecessary.

Use app.config

We used to store a lot of app settings directly as attributes, for example
app = dash.Dash(assets_ignore=...) would set app.assets_ignore.
Others would go into app.config. Now all constructor args go into
app.config, with three exceptions:
- server: can set later with app.init_app(server)
- index_string: can set later with app.index_string = 'custom string'
- plugins: can add plugins later with my_plugin.plug(app)

Some config items do not work correctly if modified later.
These are read-only in app.config.

Removed misspelled supress_callback_exceptions

Just use the correct spelling, suppress_callback_exceptions

Changed dev_tools_hot_reload_interval to seconds

Previously this run_server or enable_dev_tools setting was in
milliseconds, but dev_tools_hot_reload_watch_interval is in seconds.
Now they match!

debug smarter defaults

Changed enable_dev_tools() to have debug=True by default. Now a simple
app.enable_dev_tools() enables all the dev tools. In app.run()
it is still debug=False by default, so app.run(debug=True) is
still the correct way to enable dev tools there.

dash_core_components

Removed SyntaxHighlighter component

This is now built into dcc.Markdown using triple backticks, with optional
short or long language name on the opening line:

dcc.Markdown('''
```py
def f(a, b):
    return a + b
```
''')

Added automatic dedenting in Markdown

If all lines (other than whitespace-only or blank lines) start with the
same whitespace, it will be removed. Disable this with

dcc.Markdown(dedent=False)

Renamed Checklist.values prop to value

To match all the other input components.

Removed version.py

Until Dash v2, the simple way to get version info was dcc.__version__.
Before Dash 1.0 there was also a dash_core_components.version module you could
look in as well, but that has been removed.
As of Dash v2, there is no longer a separate dash_core_components package
at all. Now, the main dash.__version__ is all you need to know.

dash_html_components

Removed version.py

Same as in dash_core_components.
Until Dash v2, the simple way to get version info was html.__version__.
Before Dash 1.0 there was also a dash_html_components.version module you could
look in as well, but that has been removed.
As of Dash v2, there is no longer a separate dash_html_components package
at all. Now, the main dash.__version__ is all you need to know.

dash_table

Lots of properties are renamed and/or restructured for better
self-consistency and extensibility.

Additional notes

style_cell_conditional: In prior versions if.row_index was evaluated for this prop but should not have been.
Use style_data_conditional and style_header_conditional instead for if.row_index based styling.