Synthesize x/y coords for no-georef VRT reads

xrspatial/geotiff/_backends/vrt.py

@@ -571,15 +571,15 @@ def read_vrt(source: str, *,
     _vrt_is_rotated = (
         gt is not None and (gt[2] != 0.0 or gt[4] != 0.0)
     )
+    height, width = arr.shape[:2]
+    if window is not None:
+        r0 = max(0, window[0])
+        c0 = max(0, window[1])
+        coord_window = (r0, c0, r0 + height, c0 + width)
+    else:
+        coord_window = None
     if gt is not None:
         origin_x, res_x, _, origin_y, _, res_y = gt
-        height, width = arr.shape[:2]
-        if window is not None:
-            r0 = max(0, window[0])
-            c0 = max(0, window[1])
-            coord_window = (r0, c0, r0 + height, c0 + width)
-        else:
-            coord_window = None
         # Rotated VRTs emit int64 pixel coords to match the eager
         # non-VRT rotated path. Without this gate
         # the VRT branch handed back float projected coords while
@@ -594,7 +594,18 @@ def read_vrt(source: str, *,
             has_georef=not _vrt_is_rotated,
         )
     else:
-        coords = {}
+        # No ``<GeoTransform>`` at all: synthesise integer pixel coords
+        # ``0..N-1`` so a no-georef VRT carries the same x/y arrays the
+        # non-VRT no-georef read path emits (see ``_coords.py``
+        # ``has_georef=False`` fallback). Previously this branch handed
+        # back an empty coord dict, so downstream code that assumes x/y
+        # exist broke on no-georef VRTs but worked on the equivalent
+        # plain GeoTIFF.
+        coords = _coords_from_pixel_geometry(
+            0.0, 0.0, 1.0, 1.0, height, width,
+            window=coord_window,
+            has_georef=False,
+        )
 
     # Select the per-band nodata sentinel. When a specific band is
     # selected, source its nodata from that band's ``<NoDataValue>``
@@ -1099,13 +1110,12 @@ def _read_vrt_chunked(source, *, window, band, name, chunks, gpu, dtype,
     # extent. Mirrors the eager branch in ``read_vrt`` so chunked and
     # eager reads share the same x/y arrays.
     gt = vrt.geo_transform
-    coords = {}
     _vrt_is_rotated = (
         gt is not None and (gt[2] != 0.0 or gt[4] != 0.0)
     )
+    coord_window = (win_r0, win_c0, win_r0 + full_h, win_c0 + full_w)
     if gt is not None:
         origin_x, res_x, _, origin_y, _, res_y = gt
-        coord_window = (win_r0, win_c0, win_r0 + full_h, win_c0 + full_w)
         # Rotated VRTs emit int64 pixel coords to match the eager
         # non-VRT rotated path. Without this gate the
         # chunked VRT branch handed back float projected coords on a
@@ -1117,6 +1127,17 @@ def _read_vrt_chunked(source, *, window, band, name, chunks, gpu, dtype,
             window=coord_window,
             has_georef=not _vrt_is_rotated,
         )
+    else:
+        # No ``<GeoTransform>`` at all: synthesise integer pixel coords
+        # so the chunked no-georef VRT read carries the same x/y arrays
+        # the eager and non-VRT no-georef paths emit (see ``_coords.py``
+        # ``has_georef=False`` fallback). Previously this branch left
+        # ``coords = {}``, dropping x/y on no-georef VRTs.
+        coords = _coords_from_pixel_geometry(
+            0.0, 0.0, 1.0, 1.0, full_h, full_w,
+            window=coord_window,
+            has_georef=False,
+        )
 
     # Surface the nodata sentinel for the selected band. The chunked
     # path declares ``float64`` up front whenever any selected band has

xrspatial/geotiff/tests/vrt/test_parity.py

@@ -743,6 +743,61 @@ def test_vrt_chunked_none_matches_dask(tmp_path):
     assert tiff_attrs == vrt_attrs
 
 
+def test_vrt_eager_none_synthesizes_pixel_coords(tmp_path):
+    """Issue #2818: a no-``<GeoTransform>`` VRT read eagerly must
+    synthesise integer x/y pixel coords, matching the non-VRT
+    no-georef read instead of dropping coords entirely."""
+    tiff, vrt = _make_none_pair(tmp_path, 'none_coords_2818')
+    ref = open_geotiff(tiff)
+    vrt_da = read_vrt(vrt)
+    assert ref.attrs['georef_status'] == GEOREF_STATUS_NONE
+    assert vrt_da.attrs['georef_status'] == GEOREF_STATUS_NONE
+    assert 'x' in vrt_da.coords and 'y' in vrt_da.coords
+    np.testing.assert_array_equal(
+        _coord_view(vrt_da, 'x'), _coord_view(ref, 'x'))
+    np.testing.assert_array_equal(
+        _coord_view(vrt_da, 'y'), _coord_view(ref, 'y'))
+    assert vrt_da.coords['x'].dtype == ref.coords['x'].dtype
+    assert vrt_da.coords['y'].dtype == ref.coords['y'].dtype
+
+
+def test_vrt_chunked_none_synthesizes_pixel_coords(tmp_path):
+    """Issue #2818: a no-``<GeoTransform>`` VRT read chunked must
+    synthesise the same integer x/y pixel coords as the non-VRT dask
+    no-georef read rather than dropping coords entirely."""
+    tiff, vrt = _make_none_pair(tmp_path, 'none_coords_chunked_2818')
+    ref = read_geotiff_dask(tiff, chunks=2)
+    vrt_da = read_vrt(vrt, chunks=2)
+    assert ref.attrs['georef_status'] == GEOREF_STATUS_NONE
+    assert vrt_da.attrs['georef_status'] == GEOREF_STATUS_NONE
+    assert 'x' in vrt_da.coords and 'y' in vrt_da.coords
+    np.testing.assert_array_equal(
+        _coord_view(vrt_da, 'x'), _coord_view(ref, 'x'))
+    np.testing.assert_array_equal(
+        _coord_view(vrt_da, 'y'), _coord_view(ref, 'y'))
+    assert vrt_da.coords['x'].dtype == ref.coords['x'].dtype
+    assert vrt_da.coords['y'].dtype == ref.coords['y'].dtype
+
+
+def test_vrt_none_windowed_synthesizes_offset_pixel_coords(tmp_path):
+    """Issue #2818: a windowed no-georef VRT read shifts the synthesised
+    integer coords to the window offset, matching the non-VRT windowed
+    read, on both the eager and chunked paths."""
+    tiff, vrt = _make_none_pair(tmp_path, 'none_coords_win_2818')
+    window = (1, 2, 4, 4)
+    ref = open_geotiff(tiff, window=window)
+    eager = read_vrt(vrt, window=window)
+    chunked = read_vrt(vrt, window=window, chunks=2)
+    for label, actual in (('eager', eager), ('chunked', chunked)):
+        assert 'x' in actual.coords and 'y' in actual.coords, label
+        np.testing.assert_array_equal(
+            _coord_view(actual, 'x'), _coord_view(ref, 'x'),
+            err_msg=label)
+        np.testing.assert_array_equal(
+            _coord_view(actual, 'y'), _coord_view(ref, 'y'),
+            err_msg=label)
+
+
 def test_vrt_chunked_rotated_dropped(tmp_path):
     _, vrt = _make_rotated_pair(tmp_path, 'rot_chunked_2180')
     attrs = dict(read_vrt(vrt, allow_rotated=True, chunks=2).attrs)