> Explain how exactly sync is being called from within an async coroutine

⏺ Looking at the error and the code, here's exactly how sync() is being called from within an async coroutine:

  The Call Chain

  1. Test calls zarr array indexing: za[zix] in test_indexing_with_zarr_array
  2. Array.getitem (src/zarr/core/array.py:2566):
  return self.vindex[cast("CoordinateSelection | MaskSelection", selection)]
  3. VIndex.getitem (src/zarr/core/indexing.py:1248):
  return sync(self.array._async_array.vindex.getitem(selection))
  4. sync() tries to run the coroutine but detects it's already in a running loop

  The Problem

  The issue is in the __array__ method call chain:

  1. VIndex.__getitem__ calls sync() with self.array._async_array.vindex.getitem(selection)
  2. This eventually leads to AsyncArray._get_selection() being called
  3. But somewhere in the process, Array.__array__() gets called (src/zarr/core/array.py:2413)
  4. __array__() calls self[...] which goes back to Array.__getitem__
  5. This creates a nested call where sync() is called while already inside an async context

  The Root Cause

  The function _zarr_array_to_int_or_bool_array() at line 85 calls np.asarray(arr), which triggers the __array__ protocol on the zarr array. This causes:

  def _zarr_array_to_int_or_bool_array(arr: Array) -> npt.NDArray[np.intp] | npt.NDArray[np.bool_]:
      if arr.dtype.kind in ("i", "b"):
          return np.asarray(arr)  # <-- This calls arr.__array__()

  When np.asarray() is called on a zarr Array, it calls Array.__array__(), which calls self[...], which eventually calls sync() again - but we're already
  inside a sync() call from the VIndex, creating the nested async context error.

  The original code before the changes avoided this by handling the zarr array conversion within the sync methods directly, rather than delegating to async
  methods that would create this nested sync situation.