geotiff: validate tile_size and chunks size args (#1752)

`to_geotiff(..., tiled=True, tile_size=0)` reached the tiled writer
where `math.ceil(width / tile_size)` raised `ZeroDivisionError` without
naming `tile_size`. `read_geotiff_dask(chunks=0)` (or `chunks=(0, N)`)
propagated zero into dask's chunk math and surfaced as a confusing
`range()` / empty-chunks error.

Add up-front checks at both entry points that reject non-positive ints,
non-int values, and malformed `chunks` tuples with a `ValueError` that
names the parameter and the bad value. Style matches the existing
`window=` validator in `read_geotiff_dask`.

Closes #1752.

Author: brendancol

xrspatial/geotiff/__init__.py

@@ -1239,6 +1239,21 @@ def to_geotiff(data: xr.DataArray | np.ndarray,
 
     path = _coerce_path(path)
 
+    # Reject non-positive tile_size up front. The tiled writer computes
+    # the tile grid as ``math.ceil(width / tile_size)``; tile_size=0 hits
+    # ZeroDivisionError deep inside the writer, and negative values
+    # produce a nonsensical tile grid. tiled=False ignores tile_size, so
+    # only validate when tiled output is actually requested.
+    if tiled:
+        if not isinstance(tile_size, (int, np.integer)) or isinstance(
+                tile_size, bool):
+            raise ValueError(
+                f"tile_size must be a positive int, got "
+                f"{tile_size!r} (type {type(tile_size).__name__}).")
+        if tile_size <= 0:
+            raise ValueError(
+                f"tile_size must be a positive int, got tile_size={tile_size}.")
+
     # Up-front validation: catch bad compression names before they reach
     # any of the deeper write paths (streaming, GPU, VRT, COG) where the
     # error surfaces from _compression_tag with a less obvious traceback.
@@ -1908,6 +1923,33 @@ def read_geotiff_dask(source: str, *, dtype=None, chunks: int | tuple = 512,
 
     source = _coerce_path(source)
 
+    # Reject non-positive chunk sizes up front. ``chunks=0`` and negative
+    # values otherwise propagate into dask chunk math (``range(0, N, 0)``
+    # ValueError, or empty chunk grids) with no indication that ``chunks``
+    # was the problem. ``chunks`` may be an int or a (row, col) tuple.
+    if isinstance(chunks, int) and not isinstance(chunks, bool):
+        if chunks <= 0:
+            raise ValueError(
+                f"chunks must be a positive int or (row, col) tuple of "
+                f"positive ints, got chunks={chunks}.")
+    elif isinstance(chunks, tuple):
+        if len(chunks) != 2:
+            raise ValueError(
+                f"chunks tuple must have length 2 (row, col), got "
+                f"chunks={chunks!r} with length {len(chunks)}.")
+        for _v in chunks:
+            if (not isinstance(_v, (int, np.integer))
+                    or isinstance(_v, bool)
+                    or _v <= 0):
+                raise ValueError(
+                    f"chunks must be a positive int or (row, col) tuple "
+                    f"of positive ints, got chunks={chunks!r}.")
+    else:
+        raise ValueError(
+            f"chunks must be a positive int or (row, col) tuple of "
+            f"positive ints, got chunks={chunks!r} "
+            f"(type {type(chunks).__name__}).")
+
     # ``open_geotiff`` already routes ``.vrt`` to ``read_vrt`` before
     # reaching here, so this branch is only hit when ``read_geotiff_dask``
     # is called directly with a VRT path. Keep it as a defensive fallback

xrspatial/geotiff/tests/test_size_param_validation_1752.py

@@ -0,0 +1,120 @@
+"""Regression tests for issue #1752.
+
+Two public geotiff entry points used to accept size parameters without
+checking they were positive:
+
+* ``to_geotiff(..., tiled=True, tile_size=0)`` reached the tiled writer
+  where ``math.ceil(width / tile_size)`` raised ``ZeroDivisionError``,
+  with a traceback that did not name ``tile_size`` as the bad input.
+* ``read_geotiff_dask(chunks=0)`` (or ``chunks=(0, N)``) propagated zero
+  into dask's chunk math and surfaced as a confusing ``range()`` /
+  empty-chunks error.
+
+Both entry points now validate the size arguments up front and raise
+``ValueError`` naming the parameter and the invalid value.
+"""
+from __future__ import annotations
+
+import os
+
+import numpy as np
+import pytest
+import xarray as xr
+
+from xrspatial.geotiff import read_geotiff_dask, to_geotiff
+
+
+def _make_raster(tmp_path: str) -> str:
+    arr = np.arange(100, dtype=np.float32).reshape(10, 10)
+    da = xr.DataArray(
+        arr, dims=['y', 'x'],
+        coords={'y': np.arange(10), 'x': np.arange(10)},
+        attrs={'transform': (1.0, 0.0, 0.0, 0.0, -1.0, 10.0)},
+    )
+    path = os.path.join(tmp_path, 'raster.tif')
+    to_geotiff(da, path)
+    return path
+
+
+# -- to_geotiff tile_size ---------------------------------------------------
+
+
+def test_to_geotiff_tile_size_zero_raises(tmp_path):
+    arr = np.arange(100, dtype=np.float32).reshape(10, 10)
+    da = xr.DataArray(arr, dims=['y', 'x'])
+    out = os.path.join(str(tmp_path), 'out.tif')
+    with pytest.raises(ValueError, match='tile_size'):
+        to_geotiff(da, out, tiled=True, tile_size=0)
+
+
+def test_to_geotiff_tile_size_negative_raises(tmp_path):
+    arr = np.arange(100, dtype=np.float32).reshape(10, 10)
+    da = xr.DataArray(arr, dims=['y', 'x'])
+    out = os.path.join(str(tmp_path), 'out.tif')
+    with pytest.raises(ValueError, match='tile_size'):
+        to_geotiff(da, out, tiled=True, tile_size=-1)
+
+
+def test_to_geotiff_tile_size_non_int_raises(tmp_path):
+    arr = np.arange(100, dtype=np.float32).reshape(10, 10)
+    da = xr.DataArray(arr, dims=['y', 'x'])
+    out = os.path.join(str(tmp_path), 'out.tif')
+    with pytest.raises(ValueError, match='tile_size'):
+        to_geotiff(da, out, tiled=True, tile_size=256.0)
+
+
+def test_to_geotiff_tile_size_one_still_writes(tmp_path):
+    # tile_size=1 is silly but technically valid TIFF; do not reject it.
+    arr = np.arange(16, dtype=np.float32).reshape(4, 4)
+    da = xr.DataArray(arr, dims=['y', 'x'])
+    out = os.path.join(str(tmp_path), 'out.tif')
+    to_geotiff(da, out, tiled=True, tile_size=1)
+    assert os.path.exists(out)
+
+
+# -- read_geotiff_dask chunks ----------------------------------------------
+
+
+def test_read_geotiff_dask_chunks_zero_raises(tmp_path):
+    path = _make_raster(str(tmp_path))
+    with pytest.raises(ValueError, match='chunks'):
+        read_geotiff_dask(path, chunks=0)
+
+
+def test_read_geotiff_dask_chunks_negative_raises(tmp_path):
+    path = _make_raster(str(tmp_path))
+    with pytest.raises(ValueError, match='chunks'):
+        read_geotiff_dask(path, chunks=-1)
+
+
+def test_read_geotiff_dask_chunks_tuple_zero_row_raises(tmp_path):
+    path = _make_raster(str(tmp_path))
+    with pytest.raises(ValueError, match='chunks'):
+        read_geotiff_dask(path, chunks=(0, 256))
+
+
+def test_read_geotiff_dask_chunks_tuple_negative_col_raises(tmp_path):
+    path = _make_raster(str(tmp_path))
+    with pytest.raises(ValueError, match='chunks'):
+        read_geotiff_dask(path, chunks=(256, -1))
+
+
+def test_read_geotiff_dask_chunks_tuple_wrong_length_raises(tmp_path):
+    path = _make_raster(str(tmp_path))
+    with pytest.raises(ValueError, match='chunks'):
+        read_geotiff_dask(path, chunks=(64, 64, 64))
+
+
+def test_read_geotiff_dask_positive_int_chunks_works(tmp_path):
+    path = _make_raster(str(tmp_path))
+    arr = read_geotiff_dask(path, chunks=256)
+    assert arr.shape == (10, 10)
+    # Materialise to confirm the lazy graph is well-formed.
+    np.asarray(arr)
+
+
+def test_read_geotiff_dask_positive_tuple_chunks_works(tmp_path):
+    path = _make_raster(str(tmp_path))
+    arr = read_geotiff_dask(path, chunks=(4, 8))
+    assert arr.shape == (10, 10)
+    np.asarray(arr)