toolbar: work around tooltip bugs

This works around several bugs where tooltips don't close when expected.

Fixes: https://github.com/pybricks/pybricks-code/issues/275

src/utils/monkey-patch.test.tsx

@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2021 The Pybricks Authors
+
+import { Button, IRef } from '@blueprintjs/core';
+import { Tooltip2 } from '@blueprintjs/popover2';
+import {
+    fireEvent,
+    render,
+    screen,
+    waitFor,
+    waitForElementToBeRemoved,
+} from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import React from 'react';
+import { useTooltip2MonkeyPatch } from './monkey-patch';
+
+const testTooltipText = 'Test tooltip.';
+const testButtonId = 'test-button';
+
+type TestComponentProps = { monkeyPatch: boolean };
+
+const TestComponent: React.FC<TestComponentProps> = (props) => {
+    const tooltipRef = props.monkeyPatch ? useTooltip2MonkeyPatch() : undefined;
+
+    return (
+        <Tooltip2
+            ref={tooltipRef}
+            content={testTooltipText}
+            renderTarget={({
+                ref: tooltipTargetRef,
+                isOpen: _tooltipIsOpen,
+                ...tooltipTargetProps
+            }) => (
+                <Button
+                    data-testid={testButtonId}
+                    elementRef={tooltipTargetRef as IRef<HTMLButtonElement>}
+                    {...tooltipTargetProps}
+                >
+                    Press Me!
+                </Button>
+            )}
+        />
+    );
+};
+
+it.each([false, true])(
+    'should work around https://github.com/palantir/blueprint/issues/4503',
+    async (monkeyPatch) => {
+        render(<TestComponent monkeyPatch={monkeyPatch} />);
+
+        expect(screen.queryByText(testTooltipText)).not.toBeInTheDocument();
+
+        // pressing the tab key should focus the button and open the tooltip
+        userEvent.tab();
+
+        await waitFor(() => {
+            expect(screen.getByText(testTooltipText)).toBeInTheDocument();
+        });
+
+        // a blur event with renderTarget=null should trigger the bug and workaround
+        fireEvent.blur(screen.getByTestId(testButtonId));
+
+        if (monkeyPatch) {
+            // if the patch was applied, there should not be any error
+            await waitForElementToBeRemoved(screen.getByText(testTooltipText));
+        } else {
+            // if the patch was not applied, the bug should be triggered
+            try {
+                await waitForElementToBeRemoved(screen.getByText(testTooltipText));
+                fail('bug was not triggered');
+            } catch (err) {
+                // error was expected
+            }
+        }
+    },
+);