## Summary
- While rolling out RDT 5.2.0 on Fusebox, we've discovered that context
menus don't work well with this environment. The reason for it is the
context menu state implementation - in a global context we define a map
of registered context menus, basically what is shown at the moment (see
deleted Contexts.js file). These maps are not invalidated on each
re-initialization of DevTools frontend, since the bundle
(react-devtools-fusebox module) is not reloaded, and this results into
RDT throwing an error that some context menu was already registered.
- We should not keep such data in a global state, since there is no
guarantee that this will be invalidated with each re-initialization of
DevTools (like with browser extension, for example).
- The new implementation is based on a `ContextMenuContainer` component,
which will add all required `contextmenu` event listeners to the
anchor-element. This component will also receive a list of `items` that
will be displayed in the shown context menu.
- The `ContextMenuContainer` component is also using
`useImperativeHandle` hook to extend the instance of the component, so
context menus can be managed imperatively via `ref`:
`contextMenu.current?.hide()`, for example.
- **Changed**: The option for copying value to clipboard is now hidden
for functions. The reasons for it are:
- It is broken in the current implementation, because we call
`JSON.stringify` on the value, see
`packages/react-devtools-shared/src/backend/utils.js`.
- I don't see any reasonable value in doing this for the user, since `Go
to definition` option is available and you can inspect the real code and
then copy it.
- We already filter out fields from objects, if their value is a
function, because the whole object is passed to `JSON.stringify`.
## How did you test this change?
### Works with element props and hooks:
- All context menu items work reliably for props items
- All context menu items work reliably or hooks items
https://github.com/facebook/react/assets/28902667/5e2d58b0-92fa-4624-ad1e-2bbd7f12678f
### Works with timeline profiler:
- All context menu items work reliably: copying, zooming, ...
- Context menu automatically closes on the scroll event
https://github.com/facebook/react/assets/28902667/de744cd0-372a-402a-9fa0-743857048d24
### Works with Fusebox:
- Produces no errors
- Copy to clipboard context menu item works reliably
https://github.com/facebook/react/assets/28902667/0288f5bf-0d44-435c-8842-6b57bc8a7a24
* Added rudimentary context menu hook and menu UI
* Added backend support for copying a value at a specific path for the inspected element
* Added backend support for storing a value (at a specified path) as a global variable
* Added special casing to enable copying undefined/unserializable values to the clipboard
* Added copy and store-as-global context menu options to selected element props panel
* Store global variables separately, with auto-incremented name (like browsers do)
* Added tests for new copy and store-as-global backend functions
* Fixed some ownerDocument/contentWindow edge cases
* Refactored context menu to support dynamic options
Used this mechanism to add a conditional menu option for inspecting the current value (if it's a function)
* Renamed "safeSerialize" to "serializeToString" and added inline comment
