Fix _write_vrt_tiled metadata drop vs to_geotiff (#1606)

.claude/sweep-metadata-state.csv

@@ -2,3 +2,4 @@ module,last_inspected,issue,severity_max,categories_found,notes
 geotiff,2026-05-11,1598,MEDIUM,4,"read_vrt(band=N) used vrt.bands[0].nodata for attrs and integer-promotion mask, mis-masking band N reads with per-band sentinels (#1598)."
 geotiff,2026-05-11,1597,HIGH,4;5,read_geotiff_dask dropped nodata mask when sentinel only hit non-first chunks (per-chunk dtype divergence; #1597).
 reproject,2026-05-10,1572;1573,HIGH,1;3;4,geoid_height_raster dropped input attrs and used dims[-2:] for 3D inputs (#1572). reproject/merge ignored nodatavals (rasterio convention) when rioxarray absent (#1573). Fixed in same branch.
+geotiff,2026-05-11,1606,MEDIUM,1;5,_write_vrt_tiled dropped nodatavals/_FillValue aliases plus gdal_metadata/extra_tags/x_resolution/y_resolution/resolution_unit/raster_type; backend-inconsistent with to_geotiff(.tif) and write_geotiff_gpu (#1606).

xrspatial/geotiff/__init__.py

@@ -778,6 +778,61 @@ def _merge_friendly_extra_tags(extra_tags_list, attrs: dict) -> list | None:
     return existing or None
 
 
+# String identifiers (used in xrspatial attrs) -> TIFF ResolutionUnit tag ids.
+_RESOLUTION_UNIT_IDS = {'none': 1, 'inch': 2, 'centimeter': 3}
+
+
+def _extract_rich_tags(attrs: dict) -> dict:
+    """Extract the rich-tag set forwarded by the writers to ``write(...)``.
+
+    Centralises the bookkeeping shared by :func:`to_geotiff`,
+    :func:`_write_vrt_tiled`, and :func:`write_geotiff_gpu`:
+
+    * ``raster_type`` -- mapped from ``attrs['raster_type']`` ('point'
+      becomes :data:`RASTER_PIXEL_IS_POINT`; everything else stays
+      :data:`RASTER_PIXEL_IS_AREA`).
+    * ``gdal_metadata_xml`` -- prefers ``attrs['gdal_metadata_xml']``;
+      falls back to building XML from ``attrs['gdal_metadata']`` when
+      it is a dict.
+    * ``extra_tags`` -- ``attrs['extra_tags']`` folded with the friendly
+      tag attrs (image_description / extra_samples / colormap) via
+      :func:`_merge_friendly_extra_tags`.
+    * ``x_resolution`` / ``y_resolution`` -- pass-through.
+    * ``resolution_unit`` -- string label mapped to the integer tag id.
+
+    Returns a kwargs dict ready to splat into ``write(...)``: every key
+    matches the corresponding parameter name on
+    :func:`xrspatial.geotiff._writer.write`.
+    """
+    raster_type = (RASTER_PIXEL_IS_POINT
+                   if attrs.get('raster_type') == 'point'
+                   else RASTER_PIXEL_IS_AREA)
+
+    gdal_meta_xml = attrs.get('gdal_metadata_xml')
+    if gdal_meta_xml is None:
+        gdal_meta_dict = attrs.get('gdal_metadata')
+        if isinstance(gdal_meta_dict, dict):
+            from ._geotags import _build_gdal_metadata_xml
+            gdal_meta_xml = _build_gdal_metadata_xml(gdal_meta_dict)
+
+    extra_tags_list = _merge_friendly_extra_tags(
+        attrs.get('extra_tags'), attrs)
+
+    res_unit = None
+    unit_str = attrs.get('resolution_unit')
+    if unit_str is not None:
+        res_unit = _RESOLUTION_UNIT_IDS.get(str(unit_str), None)
+
+    return {
+        'raster_type': raster_type,
+        'gdal_metadata_xml': gdal_meta_xml,
+        'extra_tags': extra_tags_list,
+        'x_resolution': attrs.get('x_resolution'),
+        'y_resolution': attrs.get('y_resolution'),
+        'resolution_unit': res_unit,
+    }
+
+
 def to_geotiff(data: xr.DataArray | np.ndarray, path, *,
                crs: int | str | None = None,
                nodata=None,
@@ -1050,27 +1105,17 @@ def to_geotiff(data: xr.DataArray | np.ndarray, path, *,
                         wkt_fallback = wkt
         if nodata is None:
             nodata = _resolve_nodata_attr(data.attrs)
-        if data.attrs.get('raster_type') == 'point':
-            raster_type = RASTER_PIXEL_IS_POINT
-        gdal_meta_xml = data.attrs.get('gdal_metadata_xml')
-        if gdal_meta_xml is None:
-            gdal_meta_dict = data.attrs.get('gdal_metadata')
-            if isinstance(gdal_meta_dict, dict):
-                from ._geotags import _build_gdal_metadata_xml
-                gdal_meta_xml = _build_gdal_metadata_xml(gdal_meta_dict)
-        extra_tags_list = data.attrs.get('extra_tags')
-        # Fold friendly attrs into extra_tags so a user-edited
-        # attrs['image_description'] / ['extra_samples'] / ['colormap']
-        # actually reaches the file. Existing entries with the same tag id
-        # win, which keeps verbatim round-trips byte-stable.
-        extra_tags_list = _merge_friendly_extra_tags(
-            extra_tags_list, data.attrs)
-        x_res = data.attrs.get('x_resolution')
-        y_res = data.attrs.get('y_resolution')
-        unit_str = data.attrs.get('resolution_unit')
-        if unit_str is not None:
-            _unit_ids = {'none': 1, 'inch': 2, 'centimeter': 3}
-            res_unit = _unit_ids.get(str(unit_str), None)
+        # Pull raster_type, gdal_metadata_xml, extra_tags (folded with
+        # the friendly image_description / extra_samples / colormap
+        # attrs), x/y_resolution, and resolution_unit via the shared
+        # helper so all three writers stay in lockstep.
+        _rich = _extract_rich_tags(data.attrs)
+        raster_type = _rich['raster_type']
+        gdal_meta_xml = _rich['gdal_metadata_xml']
+        extra_tags_list = _rich['extra_tags']
+        x_res = _rich['x_resolution']
+        y_res = _rich['y_resolution']
+        res_unit = _rich['resolution_unit']
 
         # Dask-backed: stream tiles to avoid materialising the full array.
         # COG requires overviews from the full array, so it falls through
@@ -1197,8 +1242,22 @@ def to_geotiff(data: xr.DataArray | np.ndarray, path, *,
 def _write_single_tile(chunk_data, path, geo_transform, epsg, wkt,
                        nodata, compression, compression_level,
                        tile_size, predictor, bigtiff,
-                       max_z_error: float = 0.0):
-    """Write a single tile GeoTIFF. Used by _write_vrt_tiled."""
+                       max_z_error: float = 0.0,
+                       raster_type: int = RASTER_PIXEL_IS_AREA,
+                       x_resolution=None,
+                       y_resolution=None,
+                       resolution_unit=None,
+                       gdal_metadata_xml=None,
+                       extra_tags=None):
+    """Write a single tile GeoTIFF. Used by _write_vrt_tiled.
+
+    Forwards the same rich-tag set that ``to_geotiff`` passes through to
+    ``write`` (raster_type, x/y resolution, GDAL metadata, extra tags) so
+    every per-tile file under a VRT carries the same metadata it would
+    have received from a single-file ``to_geotiff(..., out.tif)`` write.
+    Without this, ``to_geotiff(da, "out.vrt")`` silently drops everything
+    except the per-tile geo_transform / crs / nodata. See issue #1606.
+    """
     if hasattr(chunk_data, 'compute'):
         chunk_data = chunk_data.compute()
     if hasattr(chunk_data, 'get'):
@@ -1234,6 +1293,12 @@ def _write_single_tile(chunk_data, path, geo_transform, epsg, wkt,
           tile_size=tile_size,
           predictor=predictor,
           compression_level=compression_level,
+          raster_type=raster_type,
+          x_resolution=x_resolution,
+          y_resolution=y_resolution,
+          resolution_unit=resolution_unit,
+          gdal_metadata_xml=gdal_metadata_xml,
+          extra_tags=extra_tags,
           bigtiff=bigtiff,
           max_z_error=max_z_error)
 
@@ -1282,6 +1347,12 @@ def _write_vrt_tiled(data, vrt_path, *, crs=None, nodata=None,
             wkt_fallback = crs
 
     geo_transform = None
+    raster_type = RASTER_PIXEL_IS_AREA
+    x_res = None
+    y_res = None
+    res_unit = None
+    gdal_meta_xml = None
+    extra_tags_list = None
 
     if isinstance(data, xr.DataArray):
         raw = data.data
@@ -1300,10 +1371,26 @@ def _write_vrt_tiled(data, vrt_path, *, crs=None, nodata=None,
                     if epsg is None and wkt_fallback is None:
                         wkt_fallback = wkt
         if nodata is None:
-            nodata = data.attrs.get('nodata')
+            # Use the same alias-aware resolver that to_geotiff /
+            # write_geotiff_gpu apply so a rioxarray-style DataArray
+            # (``attrs['nodatavals']``) or a CF-style one
+            # (``attrs['_FillValue']``) round-trips through ``.vrt``
+            # the same way it does through ``.tif``. Before this fix
+            # the VRT path used ``attrs.get('nodata')`` directly and
+            # silently dropped both aliases (issue #1606).
+            nodata = _resolve_nodata_attr(data.attrs)
         geo_transform = _transform_from_attr(data.attrs.get('transform'))
         if geo_transform is None:
             geo_transform = _coords_to_transform(data)
+        # Pull the same rich-tag set that to_geotiff forwards to
+        # ``write`` so per-tile files under the VRT carry it too.
+        _rich = _extract_rich_tags(data.attrs)
+        raster_type = _rich['raster_type']
+        gdal_meta_xml = _rich['gdal_metadata_xml']
+        extra_tags_list = _rich['extra_tags']
+        x_res = _rich['x_resolution']
+        y_res = _rich['y_resolution']
+        res_unit = _rich['resolution_unit']
     else:
         raw = data
 
@@ -1380,7 +1467,13 @@ def _write_vrt_tiled(data, vrt_path, *, crs=None, nodata=None,
                 task = dask.delayed(_write_single_tile)(
                     chunk_data, tile_path, tile_gt, epsg, wkt_fallback,
                     nodata, compression, compression_level,
-                    tile_size, predictor, bigtiff, max_z_error)
+                    tile_size, predictor, bigtiff, max_z_error,
+                    raster_type=raster_type,
+                    x_resolution=x_res,
+                    y_resolution=y_res,
+                    resolution_unit=res_unit,
+                    gdal_metadata_xml=gdal_meta_xml,
+                    extra_tags=extra_tags_list)
                 delayed_tasks.append(task)
             else:
                 # Numpy: slice and write directly
@@ -1389,7 +1482,13 @@ def _write_vrt_tiled(data, vrt_path, *, crs=None, nodata=None,
                 _write_single_tile(
                     chunk_data, tile_path, tile_gt, epsg, wkt_fallback,
                     nodata, compression, compression_level,
-                    tile_size, predictor, bigtiff, max_z_error)
+                    tile_size, predictor, bigtiff, max_z_error,
+                    raster_type=raster_type,
+                    x_resolution=x_res,
+                    y_resolution=y_res,
+                    resolution_unit=res_unit,
+                    gdal_metadata_xml=gdal_meta_xml,
+                    extra_tags=extra_tags_list)
 
             col_offset += chunk_w
         row_offset += chunk_h
@@ -2554,28 +2653,18 @@ def write_geotiff_gpu(data, path: str, *,
                         wkt_fallback = wkt
         if nodata is None:
             nodata = _resolve_nodata_attr(data.attrs)
-        if data.attrs.get('raster_type') == 'point':
-            raster_type = RASTER_PIXEL_IS_POINT
         # Mirror the CPU writer's pass-through of GDAL metadata, the
         # extra_tags list, the friendly image_description / extra_samples
         # / colormap synthesis, and the resolution tags. Without these,
         # a GPU write -> CPU read round-trip silently drops every rich
         # tag (#1563).
-        gdal_meta_xml = data.attrs.get('gdal_metadata_xml')
-        if gdal_meta_xml is None:
-            gdal_meta_dict = data.attrs.get('gdal_metadata')
-            if isinstance(gdal_meta_dict, dict):
-                from ._geotags import _build_gdal_metadata_xml
-                gdal_meta_xml = _build_gdal_metadata_xml(gdal_meta_dict)
-        extra_tags_list = data.attrs.get('extra_tags')
-        extra_tags_list = _merge_friendly_extra_tags(
-            extra_tags_list, data.attrs)
-        x_res = data.attrs.get('x_resolution')
-        y_res = data.attrs.get('y_resolution')
-        unit_str = data.attrs.get('resolution_unit')
-        if unit_str is not None:
-            _unit_ids = {'none': 1, 'inch': 2, 'centimeter': 3}
-            res_unit = _unit_ids.get(str(unit_str), None)
+        _rich = _extract_rich_tags(data.attrs)
+        raster_type = _rich['raster_type']
+        gdal_meta_xml = _rich['gdal_metadata_xml']
+        extra_tags_list = _rich['extra_tags']
+        x_res = _rich['x_resolution']
+        y_res = _rich['y_resolution']
+        res_unit = _rich['resolution_unit']
     else:
         if hasattr(data, 'compute'):
             data = data.compute()  # Dask -> CuPy or numpy