Address review: add multiband tests, BigTIFF comment, fail-fast URI check (#1084)

- Add 3D band-last and band-first streaming write tests
- Add forced bigtiff=True round-trip test
- Add cloud URI rejection test
- Note the uint32 offset limitation for BigTIFF files > 4 GB
- Move fsspec URI check to top of write_streaming for fail-fast

Author: brendancol

xrspatial/geotiff/_writer.py

@@ -1043,6 +1043,12 @@ def write_streaming(dask_data, path: str, *,
     import os
     import tempfile
 
+    # Fail fast for unsupported destinations
+    if _is_fsspec_uri(path):
+        raise NotImplementedError(
+            "Streaming dask write to cloud storage is not yet supported. "
+            "Use .compute() first or write to a .vrt file.")
+
     height, width = dask_data.shape[:2]
     samples = dask_data.shape[2] if dask_data.ndim == 3 else 1
     dtype = dask_data.dtype
@@ -1125,7 +1131,10 @@ def write_streaming(dask_data, path: str, *,
     if resolution_unit is not None:
         tags.append((TAG_RESOLUTION_UNIT, SHORT, 1, resolution_unit))
 
-    # Layout tags with placeholder offsets / byte-counts
+    # Layout tags with placeholder offsets / byte-counts.
+    # NOTE: offsets use TIFF type LONG (uint32).  For BigTIFF files
+    # exceeding 4 GB these would need LONG8 -- same limitation as the
+    # eager writer.
     placeholder = [0] * n_entries
     if tiled:
         tags.append((TAG_TILE_WIDTH, SHORT, 1, tile_size))
@@ -1184,12 +1193,6 @@ def write_streaming(dask_data, path: str, *,
                                           bigtiff=use_bigtiff)
     pixel_data_start = overflow_base + len(placeholder_overflow)
 
-    # Cloud storage not supported for streaming (needs seek)
-    if _is_fsspec_uri(path):
-        raise NotImplementedError(
-            "Streaming dask write to cloud storage is not yet supported. "
-            "Use .compute() first or write to a .vrt file.")
-
     dir_name = os.path.dirname(os.path.abspath(path))
     os.makedirs(dir_name, exist_ok=True)
     fd, tmp_path = tempfile.mkstemp(dir=dir_name, suffix='.tif.tmp')

xrspatial/geotiff/tests/test_streaming_write.py

@@ -196,6 +196,60 @@ def test_float64(self, tmp_path):
         np.testing.assert_array_almost_equal(result.values, arr)
 
 
+# -- Multiband ----------------------------------------------------------------
+
+class TestStreamingMultiband:
+    def test_3d_band_last(self, tmp_path):
+        """3D array with (y, x, band) layout."""
+        arr = np.random.default_rng(1084).random(
+            (100, 100, 3), dtype=np.float32)
+        da = xr.DataArray(arr, dims=['y', 'x', 'band'])
+        dask_da = da.chunk({'y': 50, 'x': 50})
+
+        path = str(tmp_path / 'band_last_1084.tif')
+        to_geotiff(dask_da, path)
+        result = open_geotiff(path)
+        np.testing.assert_array_almost_equal(result.values, arr, decimal=5)
+
+    def test_3d_band_first(self, tmp_path):
+        """Band-first (band, y, x) DataArray gets transposed automatically."""
+        arr = np.random.default_rng(1084).random(
+            (3, 100, 100), dtype=np.float32)
+        da = xr.DataArray(arr, dims=['band', 'y', 'x'])
+        dask_da = da.chunk({'y': 50, 'x': 50})
+
+        path = str(tmp_path / 'band_first_1084.tif')
+        to_geotiff(dask_da, path)
+        result = open_geotiff(path)
+        # Result is (y, x, band), so compare transposed
+        np.testing.assert_array_almost_equal(
+            result.values, np.moveaxis(arr, 0, -1), decimal=5)
+
+
+# -- BigTIFF and error cases --------------------------------------------------
+
+class TestStreamingBigTiffAndErrors:
+    def test_forced_bigtiff(self, tmp_path):
+        """bigtiff=True on a small array should produce a valid BigTIFF."""
+        arr = np.arange(64, dtype=np.float32).reshape(8, 8)
+        da = xr.DataArray(arr, dims=['y', 'x'])
+        dask_da = da.chunk({'y': 4, 'x': 4})
+
+        path = str(tmp_path / 'bigtiff_1084.tif')
+        to_geotiff(dask_da, path, bigtiff=True)
+        result = open_geotiff(path)
+        np.testing.assert_array_equal(result.values, arr)
+
+    def test_cloud_uri_raises(self, tmp_path):
+        """Streaming to cloud storage should raise NotImplementedError."""
+        arr = np.ones((10, 10), dtype=np.float32)
+        da = xr.DataArray(arr, dims=['y', 'x'])
+        dask_da = da.chunk({'y': 5, 'x': 5})
+
+        with pytest.raises(NotImplementedError, match='cloud'):
+            to_geotiff(dask_da, 's3://bucket/file.tif')
+
+
 # -- COG fallback to eager path -----------------------------------------------
 
 class TestCogFallback: