feat(graphiql): add data fetching hooks

Adds custom React hooks for server status polling and data fetching.

- Add usePolling hook for generic interval-based polling
- Add useServerStatus hook for checking server health
- Include comprehensive tests (386 lines)

All hook tests pass

Author: amcaplan

packages/graphiql-console/src/hooks/index.ts

@@ -0,0 +1,2 @@
+export * from './usePolling.ts'
+export * from './useServerStatus.ts'

packages/graphiql-console/src/hooks/usePolling.test.ts

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+import {usePolling} from './usePolling.ts'
+import {renderHook, act} from '@testing-library/react'
+import {vi, describe, test, expect, beforeEach, afterEach} from 'vitest'
+
+describe('usePolling', () => {
+  beforeEach(() => {
+    vi.useFakeTimers()
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  test('calls callback immediately on mount', () => {
+    const callback = vi.fn()
+    renderHook(() => usePolling(callback, {interval: 1000, enabled: true}))
+
+    expect(callback).toHaveBeenCalledTimes(1)
+  })
+
+  test('calls callback at specified interval', () => {
+    const callback = vi.fn()
+    renderHook(() => usePolling(callback, {interval: 1000, enabled: true}))
+
+    // Initial call
+    expect(callback).toHaveBeenCalledTimes(1)
+
+    // After 1 second
+    act(() => {
+      vi.advanceTimersByTime(1000)
+    })
+    expect(callback).toHaveBeenCalledTimes(2)
+
+    // After 2 seconds total
+    act(() => {
+      vi.advanceTimersByTime(1000)
+    })
+    expect(callback).toHaveBeenCalledTimes(3)
+  })
+
+  test('respects enabled=false (no polling)', () => {
+    const callback = vi.fn()
+    renderHook(() => usePolling(callback, {interval: 1000, enabled: false}))
+
+    expect(callback).not.toHaveBeenCalled()
+
+    act(() => {
+      vi.advanceTimersByTime(5000)
+    })
+
+    expect(callback).not.toHaveBeenCalled()
+  })
+
+  test('updates when callback reference changes', () => {
+    const callback1 = vi.fn()
+    const callback2 = vi.fn()
+
+    const {rerender} = renderHook(({cb}) => usePolling(cb, {interval: 1000, enabled: true}), {
+      initialProps: {cb: callback1},
+    })
+
+    // Initial call with callback1
+    expect(callback1).toHaveBeenCalledTimes(1)
+    expect(callback2).not.toHaveBeenCalled()
+
+    // Update callback
+    rerender({cb: callback2})
+
+    // Advance time - should call callback2 now
+    act(() => {
+      vi.advanceTimersByTime(1000)
+    })
+
+    // callback1 should still be at 1, callback2 should be at 1
+    expect(callback1).toHaveBeenCalledTimes(1)
+    expect(callback2).toHaveBeenCalledTimes(1)
+  })
+
+  test('cleans up interval on unmount', () => {
+    const callback = vi.fn()
+    const {unmount} = renderHook(() => usePolling(callback, {interval: 1000, enabled: true}))
+
+    expect(callback).toHaveBeenCalledTimes(1)
+
+    unmount()
+
+    // Advance time after unmount
+    act(() => {
+      vi.advanceTimersByTime(5000)
+    })
+
+    // Should not have been called again
+    expect(callback).toHaveBeenCalledTimes(1)
+  })
+
+  test('handles async callbacks', async () => {
+    const callback = vi.fn().mockResolvedValue(undefined)
+
+    renderHook(() => usePolling(callback, {interval: 1000, enabled: true}))
+
+    // Wait for initial call
+    await act(async () => {
+      await Promise.resolve()
+    })
+
+    expect(callback).toHaveBeenCalledTimes(1)
+
+    // Advance timer and wait for async call
+    await act(async () => {
+      vi.advanceTimersByTime(1000)
+      await Promise.resolve()
+    })
+
+    expect(callback).toHaveBeenCalledTimes(2)
+  })
+
+  test('catches and ignores callback errors', () => {
+    // Suppress console.error for this test since React will report the error
+    const consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {})
+
+    const callback = vi.fn().mockImplementation(() => {
+      throw new Error('Test error')
+    })
+
+    // Render the hook - errors should be caught internally
+    renderHook(() => usePolling(callback, {interval: 1000, enabled: true}))
+
+    expect(callback).toHaveBeenCalledTimes(1)
+
+    // Should continue polling despite errors
+    act(() => {
+      vi.advanceTimersByTime(1000)
+    })
+
+    expect(callback).toHaveBeenCalledTimes(2)
+
+    // Restore console.error
+    consoleErrorSpy.mockRestore()
+  })
+
+  test('changes interval dynamically', () => {
+    const callback = vi.fn()
+
+    const {rerender} = renderHook(({interval}) => usePolling(callback, {interval, enabled: true}), {
+      initialProps: {interval: 1000},
+    })
+
+    // Initial call
+    expect(callback).toHaveBeenCalledTimes(1)
+
+    // Advance by 1 second
+    act(() => {
+      vi.advanceTimersByTime(1000)
+    })
+    expect(callback).toHaveBeenCalledTimes(2)
+
+    // Change interval to 500ms - this triggers immediate call and restarts interval
+    act(() => {
+      rerender({interval: 500})
+    })
+    // Rerender triggers an immediate call due to useEffect re-running
+    expect(callback).toHaveBeenCalledTimes(3)
+
+    // Advance by 500ms - should call again
+    act(() => {
+      vi.advanceTimersByTime(500)
+    })
+    expect(callback).toHaveBeenCalledTimes(4)
+
+    // Another 500ms
+    act(() => {
+      vi.advanceTimersByTime(500)
+    })
+    expect(callback).toHaveBeenCalledTimes(5)
+  })
+})

packages/graphiql-console/src/hooks/usePolling.ts

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+import {useEffect, useRef} from 'react'
+
+interface UsePollingOptions {
+  // Polling interval in milliseconds
+  interval: number
+  // Whether polling is active (default: true)
+  enabled?: boolean
+}
+
+/**
+ * Generic polling hook that calls a function at regular intervals
+ * @param callback - Function to call on each interval
+ * @param options - Polling configuration
+ */
+export function usePolling(callback: () => void | Promise<void>, options: UsePollingOptions) {
+  const {interval, enabled = true} = options
+  const callbackRef = useRef(callback)
+
+  // Keep callback ref up-to-date
+  useEffect(() => {
+    callbackRef.current = callback
+  }, [callback])
+
+  useEffect(() => {
+    if (!enabled) return
+
+    const executeCallback = () => {
+      try {
+        Promise.resolve(callbackRef.current()).catch(() => {
+          // Intentionally ignore errors in polling callbacks
+        })
+        // eslint-disable-next-line no-catch-all/no-catch-all
+      } catch {
+        // Intentionally ignore synchronous errors in polling callbacks
+      }
+    }
+
+    // Call immediately on mount
+    executeCallback()
+
+    // Set up interval
+    const intervalId = setInterval(executeCallback, interval)
+
+    return () => clearInterval(intervalId)
+  }, [interval, enabled])
+}