Add crs_units and crs_name to from_template() result.attrs

xrspatial/reproject/_lite_crs.py

@@ -286,6 +286,15 @@ def is_geographic(self) -> bool:
         """True if this CRS is geographic (lat/lon), False if projected."""
         return self._entry["_is_geographic"]
 
+    @property
+    def name(self) -> str:
+        """Human-readable CRS name, e.g. ``"NAD83 / Conus Albers"``.
+
+        Mirrors ``pyproj.CRS.name``. Falls back to ``"EPSG:<code>"`` for
+        table entries without a curated name.
+        """
+        return self._entry.get("_name", f"EPSG:{self._epsg}")
+
     # -- output methods ------------------------------------------------
 
     def to_epsg(self) -> int:

xrspatial/templates.py

@@ -173,6 +173,20 @@ def _make_data(shape, fill, backend, chunks):
     )
 
 
+def _crs_name(crs):
+    """Best-effort human-readable name for an EPSG code.
+
+    Resolves through the same two-tier path as the rest of the library
+    (built-in ``LiteCRS`` table first, pyproj fallback). Returns ``None``
+    when the code is outside the built-in table and pyproj is not
+    installed, so the default (non-reproject) path stays dependency-free.
+    """
+    try:
+        return _resolve_crs(crs).name
+    except (ImportError, ValueError, TypeError):
+        return None
+
+
 def from_template(name, resolution=None, *, preserve=None, backend="numpy",
                   fill=np.nan, chunks="auto"):
     """Create an empty DataArray for a common study area.
@@ -220,7 +234,11 @@ def from_template(name, resolution=None, *, preserve=None, backend="numpy",
     -------
     template : xarray.DataArray
         Empty 2-D raster with ``dims=('y', 'x')``, pixel-center coordinates,
-        and ``attrs`` carrying ``res`` and ``crs``.
+        and ``attrs`` carrying ``res``, ``crs``, ``crs_units`` (``'m'`` or
+        ``'degree'``), and ``crs_name`` (the projection's human-readable
+        name, e.g. ``'NAD83 / Conus Albers'``). ``crs_name`` is omitted only
+        when the EPSG code is outside the built-in table and pyproj is not
+        installed.
 
     Examples
     --------
@@ -284,14 +302,21 @@ def from_template(name, resolution=None, *, preserve=None, backend="numpy",
     ys, xs = _make_output_coords((left, bottom, right, top), (height, width))
 
     data = _make_data((height, width), fill, backend, chunks)
+    # Every template emits either EPSG:4326 (country codes, degrees) or a
+    # metre-based projected CRS (curated regions and all preserve paths).
     unit = "degree" if crs == 4326 else "m"
 
+    attrs = {"res": (res_x, res_y), "crs": crs, "crs_units": unit}
+    crs_name = _crs_name(crs)
+    if crs_name is not None:
+        attrs["crs_name"] = crs_name
+
     template = xr.DataArray(
         data,
         name=key,
         coords={"y": ys, "x": xs},
         dims=["y", "x"],
-        attrs={"res": (res_x, res_y), "crs": crs},
+        attrs=attrs,
     )
     template["x"].attrs["units"] = unit
     template["y"].attrs["units"] = unit

xrspatial/tests/test_templates.py

@@ -339,3 +339,49 @@ def test_preserve_downstream_slope():
         warnings.simplefilter("ignore", RuntimeWarning)
         out = slope(agg)
     assert out.shape == agg.shape
+
+
+def test_crs_units_attr():
+    # crs_units mirrors the coordinate units: metres for a projected
+    # template, degrees for a country code in EPSG:4326.
+    proj = from_template("conus")
+    assert proj.attrs["crs_units"] == "m" == proj.x.attrs["units"]
+    geo = from_template("FRA")
+    assert geo.attrs["crs_units"] == "degree" == geo.x.attrs["units"]
+
+
+def test_crs_name_attr():
+    # 5070 is in the built-in LiteCRS table, so the name is deterministic
+    # regardless of whether pyproj is installed.
+    assert from_template("conus").attrs["crs_name"] == "NAD83 / Conus Albers"
+    assert from_template("FRA").attrs["crs_name"] == "WGS 84"
+
+
+def test_crs_name_preserve_path():
+    # The preserve path requires pyproj, so the chosen projection's name
+    # is always available.
+    name = from_template("conus", preserve="area").attrs["crs_name"]
+    assert name == "NAD83 / Conus Albers"
+
+
+def test_crs_name_omitted_without_pyproj(monkeypatch):
+    # When the EPSG code is outside the built-in table and pyproj can't be
+    # imported, crs_name is left off rather than raising.
+    import xrspatial.templates as templates
+
+    def _no_crs(_crs):
+        raise ImportError("pyproj not installed")
+
+    monkeypatch.setattr(templates, "_resolve_crs", _no_crs)
+    agg = from_template("conus")
+    assert "crs_name" not in agg.attrs
+    # The rest of the contract still holds.
+    assert agg.attrs["crs"] == 5070
+    assert agg.attrs["crs_units"] == "m"
+
+
+def test_lite_crs_name_property():
+    from xrspatial.reproject._lite_crs import CRS as LiteCRS
+
+    assert LiteCRS(5070).name == "NAD83 / Conus Albers"
+    assert LiteCRS(4326).name == "WGS 84"