v.what.rast: Sample points on the southern and eastern edge

vector/v.what.rast/main.c

@@ -286,6 +286,14 @@ int main(int argc, char *argv[])
         /* Add point to cache */
         row = Rast_northing_to_row(Points->y[0], &window);
         col = Rast_easting_to_col(Points->x[0], &window);
+
+        /* The southern and eastern edges convert to the first row or column
+         * outside the region, so bring points there into the last one. */
+        if (Points->y[0] == window.south)
+            row = window.rows - 1;
+        if (Points->x[0] == window.east)
+            col = window.cols - 1;
+
         if (col < 0 || col >= window.cols || row < 0 || row >= window.rows)
             continue;
 

vector/v.what.rast/tests/v_what_rast_test.py

@@ -0,0 +1,107 @@
+import os
+from io import StringIO
+
+import pytest
+
+import grass.script as gs
+from grass.tools import Tools
+
+# Points sampled in the tests, as cat: (easting, northing).
+# The region is 10 by 10 cells with n=10, s=0, e=10, w=0 and res=1.
+POINTS = {
+    1: (0.5, 9.5),  # interior, first row and column
+    2: (9.5, 0.5),  # interior, last row and column
+    3: (5.5, 0),  # southern edge
+    4: (10, 5.5),  # eastern edge
+    5: (10, 0),  # south-eastern corner
+    6: (0, 9.5),  # western edge
+    7: (5.5, 10),  # northern edge
+}
+
+# Values of grid = (row() - 1) * 10 + col() at those points, as reported by
+# r.what, which brings the southern and eastern edges into the region.
+EXPECTED = {1: 1, 2: 100, 3: 96, 4: 50, 5: 100, 6: 1, 7: 6}
+
+
+@pytest.fixture
+def session_with_points(tmp_path):
+    """A GRASS session with a grid raster and points on the region edges.
+
+    The raster encodes its own cell position, so the value tells which cell
+    was sampled.
+    """
+    project = tmp_path / "v_what_rast_project"
+    gs.create_project(project)
+    with gs.setup.init(project, env=os.environ.copy()) as session:
+        tools = Tools(session=session)
+        tools.g_region(n=10, s=0, e=10, w=0, res=1)
+        tools.r_mapcalc(expression="grid = (row() - 1) * 10 + col()")
+        text = "".join(f"{cat}|{x}|{y}\n" for cat, (x, y) in POINTS.items())
+        tools.v_in_ascii(
+            input=StringIO(text),
+            output="points",
+            separator="|",
+            x=2,
+            y=3,
+            cat=1,
+            columns="cat integer, x double precision, y double precision",
+        )
+        tools.v_db_addtable(map="points", columns="value integer")
+        yield session
+
+
+def sampled_values(tools):
+    """Run v.what.rast and return the sampled value per category."""
+    tools.v_what_rast(map="points", raster="grid", column="value")
+    records = tools.v_db_select(map="points", format="json").json["records"]
+    return {record["cat"]: record["value"] for record in records}
+
+
+@pytest.mark.parametrize("cat", [3, 4, 5], ids=["south", "east", "corner"])
+def test_points_on_south_and_east_edge_are_sampled(session_with_points, cat):
+    """Points on the southern or eastern edge are inside the region.
+
+    Those edges belong to the first cell beyond the region, so they have to be
+    brought into the last row or column instead of being dropped.
+    """
+    tools = Tools(session=session_with_points)
+
+    assert sampled_values(tools)[cat] == EXPECTED[cat]
+
+
+@pytest.mark.parametrize("cat", [1, 2, 6, 7], ids=["nw", "se", "west", "north"])
+def test_points_inside_region_are_sampled(session_with_points, cat):
+    """Interior points and the northern and western edges are sampled."""
+    tools = Tools(session=session_with_points)
+
+    assert sampled_values(tools)[cat] == EXPECTED[cat]
+
+
+def test_values_agree_with_r_what(session_with_points):
+    """v.what.rast and r.what report the same value for the same coordinates."""
+    tools = Tools(session=session_with_points)
+    values = sampled_values(tools)
+
+    for cat, coordinates in POINTS.items():
+        queried = tools.r_what(map="grid", coordinates=coordinates, format="json").json
+        assert values[cat] == queried[0]["grid"]["value"], f"category {cat}"
+
+
+def test_points_outside_region_are_not_sampled(session_with_points):
+    """Points beyond the region are still reported as outside and skipped."""
+    tools = Tools(session=session_with_points)
+    tools.v_in_ascii(
+        input=StringIO("8|20|20\n"),
+        output="outside",
+        separator="|",
+        x=2,
+        y=3,
+        cat=1,
+        columns="cat integer, x double precision, y double precision",
+    )
+    tools.v_db_addtable(map="outside", columns="value integer")
+
+    tools.v_what_rast(map="outside", raster="grid", column="value")
+
+    records = tools.v_db_select(map="outside", format="json").json["records"]
+    assert records[0]["value"] is None