Dash

Added
- [672](https://github.com/plotly/dash/pull/672), [renderer#143](https://github.com/plotly/dash-renderer/pull/143) Support for "Clientside Callbacks" - an escape hatch to execute your callbacks in JavaScript instead of Python
- [676](https://github.com/plotly/dash/pull/676) Add `dev_tools_ui` config flag in `app.run_server` (serialized in `<script id="_dash-config" type="application/json">`) to display or hide the forthcoming Dev Tools UI in Dash's front-end (dash-renderer).
- [680](https://github.com/plotly/dash/pull/680) Partial updates: leave some multi-output updates unchanged while updating others

Removed
- [renderer145](https://github.com/plotly/dash-renderer/pull/145) Remove `dash_renderer._set_react_version` support for 15.4.2 and 16.2.0

Changed
- Bump dash-core-components version from 0.45.0 to [0.46.0](https://github.com/plotly/dash-core-components/blob/master/CHANGELOG.md#0460---2019-04-10)
- [renderer145](https://github.com/plotly/dash-renderer/pull/145) Update from React 15.4.2 to React 16.8.6

Changed
- Bump dash-core-components version from 0.44.0 to [0.45.0](https://github.com/plotly/dash-core-components/blob/master/CHANGELOG.md#0450---2019-03-25)
- Bump dash-html-components version from 0.14.0 to [0.15.0](https://github.com/plotly/dash-html-components/blob/master/CHANGELOG.md#0150---2019-03-25)
- [renderer140](https://github.com/plotly/dash-renderer/pull/140), [renderer#126](https://github.com/plotly/dash-renderer/pull/126) Optimize rendering, and always assign `setProps` to components even with no callbacks to use it.

Added
- [436](https://github.com/plotly/dash/pull/436) Allow multiple outputs from a single callback.
- [367](https://github.com/plotly/dash/pull/367) Support custom JavaScript hooks to modify callback payloads and responses.
- [623](https://github.com/plotly/dash/pull/623) Modify the flask response with custom cookies or headers, using `dash.callback_context.response`.
- [renderer93](https://github.com/plotly/dash-renderer/pull/93) Loading states API

Changed
- Bump dash-core-components version from 0.43.1 to [0.44.0](https://github.com/plotly/dash-core-components/blob/master/CHANGELOG.md#0440---2019-03-04)
- Bump dash-html-components version from 0.13.5 to [0.14.0](https://github.com/plotly/dash-html-components/blob/master/CHANGELOG.md#0140---2019-03-04)
- Bump dash-table version from 3.5.0 to [3.6.0](https://github.com/plotly/dash-table/blob/master/CHANGELOG.md#360---2019-03-04)

Added
- [603](https://github.com/plotly/dash/pull/603) Add components libraries js/css distribution to hot reload watch.
- [608](https://github.com/plotly/dash/pull/608), [renderer#124](https://github.com/plotly/dash-renderer/pull/124) Callback context:
- Know which inputs caused a callback to fire: `dash.callback_context.triggered`
- Input/State values by name `dash.callback_context.states.get('btn.n_clicks')`

Changed
- Bump dash-table version from 3.4.0 to [3.5.0](https://github.com/plotly/dash-table/blob/master/CHANGELOG.md#350---2019-02-25)
- Bump dash-renderer version from 0.18.0 to [0.19.0](https://github.com/plotly/dash-renderer/blob/master/CHANGELOG.md#0190---2019-02-25)

Fixed
- Fix missing indentation for generated metadata.json [600](https://github.com/plotly/dash/issues/600)
- Fix missing component prop docstring error [598](https://github.com/plotly/dash/issues/598)
- [492](https://github.com/plotly/dash/pull/492) Move `__repr__` to base component instead of being generated.
- [605](https://github.com/plotly/dash/pull/605) Raise exception when same input & output are used in a callback

Removed
- [renderer118](https://github.com/plotly/dash-renderer/pull/118) Removed redux logger for the dev.

Changed
- [565](https://github.com/plotly/dash/pull/565) Add core libraries as version locked dependencies
- Bump dash-table version from 3.3.0 to [3.4.0](https://github.com/plotly/dash-table/blob/master/CHANGELOG.md#340---2019-02-08)
- Bump dash-renderer version from 0.17.0 to [0.18.0](https://github.com/plotly/dash-renderer/blob/master/CHANGELOG.md#0180---2019-02-11)
- Bump dash-core-components version from 0.43.0 to [0.43.1](https://github.com/plotly/dash-core-components/blob/master/CHANGELOG.md#0431---2019-02-11)

Fixed
- [563](https://github.com/plotly/dash/pull/563) Fix collections.abc deprecation warning for Python 3.8

Removed
- [550](https://github.com/plotly/dash/pull/550), [renderer#114](https://github.com/plotly/dash-renderer/pull/114) Remove support for `Event` system. Use event properties instead, for example the `n_clicks` property instead of the `click` event, see [#531](https://github.com/plotly/dash/issues/531). `dash_renderer` MUST be upgraded to >=0.17.0 together with this, and it is recommended to update `dash_core_components` to >=0.43.0 and `dash_html_components` to >=0.14.0.