[core] feat(HotkeysProvider): support advanced nesting use cases

packages/core/src/components/hotkeys/hotkeys-target2.md

@@ -18,7 +18,7 @@ Migrating from [HotkeysTarget](#core/components/hotkeys)?
 HotkeysTarget2 is a replacement for HotkeysTarget. You are encouraged to use this new API, or
 the `useHotkeys` hook directly in your function components, as they will become the standard
 APIs in Blueprint v4. See the full
-[migration guide](https://github.com/palantir/blueprint/wiki/useHotkeys-migration) on the wiki.
+[migration guide](https://github.com/palantir/blueprint/wiki/HotkeysTarget-&-useHotkeys-migration) on the wiki.
 
 </div>
 

packages/core/src/components/hotkeys/hotkeys.md

@@ -9,7 +9,7 @@ Deprecated: use [useHotkeys](#core/hooks/use-hotkeys)
 
 This API is **deprecated since @blueprintjs/core v3.39.0** in favor of the new
 [`useHotkeys` hook](#core/hooks/use-hotkeys) and
-[HotkeysTarget2 component](#core/components/hokeys-target2) available to React 16.8+ users.
+[HotkeysTarget2 component](#core/components/hotkeys-target2) available to React 16.8+ users.
 You should migrate to one of these new APIs, as they will become the standard in Blueprint v4.
 
 </div>

packages/core/src/context/hotkeys/hotkeys-provider.md

@@ -17,7 +17,7 @@ Migrating from [HotkeysTarget](#core/components/hotkeys)?
 
 HotkeysProvider and `useHotkeys`, used together, are a replacement for HotkeysTarget.
 You are encouraged to use this new API, as it will become the standard APIs in Blueprint v4.
-See the full [migration guide](https://github.com/palantir/blueprint/wiki/useHotkeys-migration)
+See the full [migration guide](https://github.com/palantir/blueprint/wiki/HotkeysTarget-&-useHotkeys-migration)
 on the wiki.
 
 </div>
@@ -43,6 +43,84 @@ ReactDOM.render(
 );
 ```
 
+@## Advanced usage
+
+HotkeysProvider should not be nested, except in special cases. If you have a rendering boundary within your application
+through which React context is not preserved (for example, a plugin system which uses `ReactDOM.render()`) and you wish
+to use hotkeys in a descendant part of the tree below such a boundary, you may render a descendant provider and initialize
+it with the root context instance. This ensures that there will only be one "global" hotkeys dialogs in an application
+which has multiple HotkeysProviders.
+
+```tsx
+import {
+    HotkeyConfig,
+    HotkeysContext,
+    HotkeysProvider,
+    HotkeysTarget2
+} from "@blueprintjs/core";
+import React, { useContext, useEffect, useRef } from "react";
+import ReactDOM from "react-dom";
+
+function App() {
+    const appHotkeys: HotkeyConfig[] = [
+        {
+            combo: "o",
+            global: true,
+            label: "Open",
+            onKeyDown: () => console.info("open"),
+        },
+    ];
+
+    return (
+        <HotkeysProvider>
+            <div>
+                <HotkeysTarget2 hotkeys={appHotkeys}>
+                    <div>My app has hotkeys 😎</div>
+                </HotkeysTarget2>
+                <PluginSlot>
+                    <Plugin />
+                </PluginSlot>
+            </div>
+        </HotkeysProvider>
+    );
+}
+
+function Plugin() {
+    const pluginHotkeys: HotkeyConfig[] = [
+        {
+            combo: "f",
+            global: true,
+            label: "Search",
+            onKeyDown: () => console.info("search"),
+        }
+    ];
+
+    return (
+        <HotkeysTarget2 hotkeys={pluginHotkeys}>
+            <div>This plugin also has hotkeys</div>
+        </HotkeysTarget2>
+    );
+}
+
+function PluginSlot(props) {
+    const hotkeysContext = useContext(HotkeysContext);
+    const ref = useRef<HTMLDivElement>();
+
+    useEffect(() => {
+        if (ref.current != null) {
+            ReactDOM.render(
+                <HotkeysProvider value={hotkeysContext}>
+                    {props.children}
+                </HotkeysProvider>,
+                ref.current,
+            );
+        }
+    }, [ref, hotkeysContext, props.children]);
+
+    return <div ref={ref} />;
+}
+```
+
 @## Props
 
 @interface HotkeysProviderProps

packages/core/src/context/hotkeys/hotkeysProvider.tsx

@@ -31,14 +31,23 @@ type HotkeysAction =
     | { type: "ADD_HOTKEYS" | "REMOVE_HOTKEYS"; payload: HotkeyConfig[] }
     | { type: "CLOSE_DIALOG" | "OPEN_DIALOG" };
 
+export type HotkeysContextInstance = [HotkeysContextState, React.Dispatch<HotkeysAction>];
+
 const initialHotkeysState: HotkeysContextState = { hotkeys: [], isDialogOpen: false };
 const noOpDispatch: React.Dispatch<HotkeysAction> = () => null;
 
-// we can remove this guard once Blueprint depends on React 16
-export const HotkeysContext = React.createContext?.<[HotkeysContextState, React.Dispatch<HotkeysAction>]>([
-    initialHotkeysState,
-    noOpDispatch,
-]);
+// N.B. we can remove this optional call guard once Blueprint depends on React 16
+/**
+ * A React context used to register and deregister hotkeys as components are mounted and unmounted in an application.
+ * Users should take care to make sure that only _one_ of these is instantiated and used within an application, especially
+ * if using global hotkeys.
+ *
+ * You will likely not be using this HotkeysContext directly, except in cases where you need to get a direct handle on an
+ * exisitng context instance for advanced use cases involving nested HotkeysProviders.
+ *
+ * For more information, see the [HotkeysProvider documentation](https://blueprintjs.com/docs/#core/context/hotkeys-provider).
+ */
+export const HotkeysContext = React.createContext?.<HotkeysContextInstance>([initialHotkeysState, noOpDispatch]);
 
 const hotkeysReducer = (state: HotkeysContextState, action: HotkeysAction) => {
     switch (action.type) {
@@ -70,13 +79,17 @@ export interface HotkeysProviderProps {
 
     /** If provided, this dialog render function will be used in place of the default implementation. */
     renderDialog?: (state: HotkeysContextState, contextActions: { handleDialogClose: () => void }) => JSX.Element;
+
+    /** If provided, we will use this context instance instead of generating our own. */
+    value?: HotkeysContextInstance;
 }
 
 /**
  * Hotkeys context provider, necessary for the `useHotkeys` hook.
  */
-export const HotkeysProvider = ({ children, dialogProps, renderDialog }: HotkeysProviderProps) => {
-    const [state, dispatch] = React.useReducer(hotkeysReducer, initialHotkeysState);
+export const HotkeysProvider = ({ children, dialogProps, renderDialog, value }: HotkeysProviderProps) => {
+    const hasExistingContext = value != null;
+    const [state, dispatch] = value ?? React.useReducer(hotkeysReducer, initialHotkeysState);
     const handleDialogClose = React.useCallback(() => dispatch({ type: "CLOSE_DIALOG" }), []);
 
     const dialog = renderDialog?.(state, { handleDialogClose }) ?? (
@@ -88,10 +101,11 @@ export const HotkeysProvider = ({ children, dialogProps, renderDialog }: Hotkeys
         />
     );
 
+    // if we are working with an existing context, we don't need to generate our own dialog
     return (
         <HotkeysContext.Provider value={[state, dispatch]}>
             {children}
-            {dialog}
+            {hasExistingContext ? undefined : dialog}
         </HotkeysContext.Provider>
     );
 };

packages/core/src/context/index.ts

@@ -14,4 +14,9 @@
  * limitations under the License.
  */
 
-export { HotkeysContext, HotkeysProvider, HotkeysProviderProps } from "./hotkeys/hotkeysProvider";
+export {
+    HotkeysContext,
+    HotkeysContextInstance,
+    HotkeysProvider,
+    HotkeysProviderProps,
+} from "./hotkeys/hotkeysProvider";

packages/core/src/hooks/hotkeys/use-hotkeys.md

@@ -18,7 +18,7 @@ Migrating from [HotkeysTarget](#core/components/hotkeys)?
 `useHotkeys` is a replacement for HotkeysTarget. You are encouraged to use this new API in your function
 components, or the [HotkeysTarget2 component](#core/components/hotkeys-target2) in your component classes,
 as they will become the standard APIs in Blueprint v4. See the full
-[migration guide](https://github.com/palantir/blueprint/wiki/useHotkeys-migration) on the wiki.
+[migration guide](https://github.com/palantir/blueprint/wiki/HotkeysTarget-&-useHotkeys-migration) on the wiki.
 
 </div>
 

packages/core/src/hooks/hotkeys/useHotkeys.ts

@@ -79,12 +79,18 @@ export function useHotkeys(keys: HotkeyConfig[], options: UseHotkeysOptions = {}
     ) => {
         const isTextInput = isTargetATextInput(e);
         for (const key of global ? globalKeys : localKeys) {
-            const shouldIgnore = (isTextInput && !key.config.allowInInput) || key.config.disabled;
+            const {
+                allowInInput = false,
+                disabled = false,
+                preventDefault = false,
+                stopPropagation = false,
+            } = key.config;
+            const shouldIgnore = (isTextInput && !allowInInput) || disabled;
             if (!shouldIgnore && comboMatches(key.combo, combo)) {
-                if (key.config.preventDefault) {
+                if (preventDefault) {
                     e.preventDefault();
                 }
-                if (key.config.stopPropagation) {
+                if (stopPropagation) {
                     // set a flag just for unit testing. not meant to be referenced in feature work.
                     (e as any).isPropagationStopped = true;
                     e.stopPropagation();