Test that shows jinja can use generator functions

To keep the load small, we need to write files via generators,
not simply via one big string.
Using file.writelines() is buffered, and the dask array is buffered.

Author: deltamarnix

flopy4/xarray_jinja/filters.py

@@ -0,0 +1,12 @@
+import numpy as np
+import xarray as xr
+
+
+def dask_expand(data: xr.DataArray):
+    for block in data.data.blocks:
+        block_data = block.compute()
+        yield block_data
+
+
+def nparray2string(data: np.ndarray):
+    return " ".join(data.astype(str))

flopy4/xarray_jinja/templates/disu_template.disu.jinja

@@ -0,0 +1,5 @@
+BEGIN GRIDDATA
+{% for chunk in data | dask_expand %}
+{{chunk | nparray2string }}
+{% endfor %}
+END GRIDDATA

test/test_xarray_jinja.py

@@ -0,0 +1,28 @@
+import dask.array as da
+import jinja2
+import xarray as xr
+
+import flopy4.xarray_jinja.filters as filters
+
+
+def test_xarray_to_text_jinja(tmp_path):
+    data = xr.DataArray(da.arange(0, 10_000, 1), dims="x")
+    data = data.chunk(100)
+
+    env = jinja2.Environment(
+        loader=jinja2.PackageLoader("flopy4.xarray_jinja"),
+        trim_blocks=True,
+        lstrip_blocks=True,
+    )
+    env.filters["dask_expand"] = filters.dask_expand
+    env.filters["nparray2string"] = filters.nparray2string
+
+    generator = env.get_template("disu_template.disu.jinja").generate(
+        data=data
+    )
+    with open(tmp_path / "test_xarray_to_text_jinja.disu", "w") as f:
+        f.writelines(generator)
+
+    with open(tmp_path / "test_xarray_to_text_jinja.disu", "r") as f:
+        output = f.readlines()
+        assert len(output) == 102  # begin + end + 100 lines of data