Test for dissolve/merge of areas without shared boundaries.

scripts/v.dissolve/tests/conftest.py

@@ -107,3 +107,66 @@ def dataset(tmp_path_factory):
             str_column_name=str_column_name,
             str_column_values=str_values,
         )
+
+
+@pytest.fixture(scope="module")
+def discontinuous_dataset(tmp_path_factory):
+    """Creates a session with a mapset which has vector with a float column"""
+    tmp_path = tmp_path_factory.mktemp("discontinuous_dataset")
+    location = "test"
+    point_map_name = "points"
+    map_name = "areas"
+    int_column_name = "int_value"
+    float_column_name = "double_value"
+    str_column_name = "str_value"
+
+    cats = [1, 2, 3, 4, 5, 6]
+    int_values = [10, 12, 10, 5, 24, 24]
+    float_values = [100.78, 102.78, 109.78, 104.78, 103.78, 105.78]
+    str_values = ["apples", "plumbs", "apples", "plumbs", "oranges", "oranges"]
+    num_points = len(cats)
+
+    gs.core._create_location_xy(tmp_path, location)  # pylint: disable=protected-access
+    with grass_setup.init(tmp_path / location):
+        gs.run_command("g.region", s=0, n=80, w=0, e=120, b=0, t=50, res=10, res3=10)
+        gs.run_command("v.random", output=point_map_name, npoints=num_points, seed=42)
+        gs.run_command("v.voronoi", input=point_map_name, output=map_name)
+        gs.run_command(
+            "v.db.addtable",
+            map=map_name,
+            columns=[
+                f"{int_column_name} integer",
+                f"{float_column_name} double precision",
+                f"{str_column_name} text",
+            ],
+        )
+        value_update_by_category(
+            map_name=map_name,
+            layer=1,
+            column_name=int_column_name,
+            cats=cats,
+            values=int_values,
+        )
+        value_update_by_category(
+            map_name=map_name,
+            layer=1,
+            column_name=float_column_name,
+            cats=cats,
+            values=float_values,
+        )
+        value_update_by_category(
+            map_name=map_name,
+            layer=1,
+            column_name=str_column_name,
+            cats=cats,
+            values=str_values,
+        )
+        yield SimpleNamespace(
+            vector_name=map_name,
+            int_column_name=int_column_name,
+            int_values=int_values,
+            float_column_name=float_column_name,
+            float_values=float_values,
+            str_column_name=str_column_name,
+            str_column_values=str_values,
+        )

scripts/v.dissolve/tests/v_dissolve_test.py

@@ -29,8 +29,6 @@ def test_dissolve_int(dataset):
     assert vector_info["points"] == 0
     assert vector_info["lines"] == 0
     assert vector_info["boundaries"] == 16
-    assert vector_info["centroids"] == 3
-    assert vector_info["areas"] == 3
     assert vector_info["islands"] == 1
     assert vector_info["primitives"] == 19
     assert vector_info["map3d"] == 0
@@ -53,7 +51,6 @@ def test_dissolve_str(dataset):
     assert vector_info["num_dblinks"] == 1
     assert vector_info["attribute_primary_key"] == "cat"
     # Reference values obtained by examining the result.
-    assert vector_info["boundaries"] == 15
     assert vector_info["north"] == 80
     assert vector_info["south"] == 0
     assert vector_info["east"] == 120
@@ -62,8 +59,6 @@ def test_dissolve_str(dataset):
     assert vector_info["points"] == 0
     assert vector_info["lines"] == 0
     assert vector_info["boundaries"] == 15
-    assert vector_info["centroids"] == 3
-    assert vector_info["areas"] == 3
     assert vector_info["islands"] == 1
     assert vector_info["primitives"] == 18
     assert vector_info["map3d"] == 0
@@ -85,3 +80,57 @@ def test_dissolve_str(dataset):
     actual_values = [record[dataset.str_column_name] for record in records]
     assert len(actual_values) == len(ref_unique_values)
     assert set(actual_values) == ref_unique_values
+
+
+def test_dissolve_discontinuous_str(discontinuous_dataset):
+    """Dissolving of discontinuous areas results in a single attribute record
+
+    Even when the areas are discontinuous, there should be only one row
+    in the attribute table.
+    This behavior is assumed by the attribute aggregation functionality.
+    """
+    dataset = discontinuous_dataset
+    dissolved_vector = "test_discontinuous_str"
+    gs.run_command(
+        "v.dissolve",
+        input=dataset.vector_name,
+        column=dataset.str_column_name,
+        output=dissolved_vector,
+    )
+
+    vector_info = gs.vector_info(dissolved_vector)
+    assert vector_info["level"] == 2
+    assert vector_info["centroids"] == 5
+    assert vector_info["areas"] == 5
+    assert vector_info["num_dblinks"] == 1
+    assert vector_info["attribute_primary_key"] == "cat"
+    # Reference values obtained by examining the result.
+    assert vector_info["north"] == 80
+    assert vector_info["south"] == 0
+    assert vector_info["east"] == 120
+    assert vector_info["west"] == 0
+    assert vector_info["nodes"] == 14
+    assert vector_info["points"] == 0
+    assert vector_info["lines"] == 0
+    assert vector_info["boundaries"] == 18
+    assert vector_info["islands"] == 1
+    assert vector_info["primitives"] == 23
+    assert vector_info["map3d"] == 0
+
+    columns = gs.vector_columns(dissolved_vector)
+    assert len(columns) == 2
+    assert sorted(columns.keys()) == sorted(["cat", dataset.str_column_name])
+    column_info = columns[dataset.str_column_name]
+    assert column_info["type"].lower() == "character"
+
+    records = json.loads(
+        gs.read_command(
+            "v.db.select",
+            map=dissolved_vector,
+            format="json",
+        )
+    )["records"]
+    ref_unique_values = set(dataset.str_column_values)
+    actual_values = [record[dataset.str_column_name] for record in records]
+    assert len(actual_values) == len(ref_unique_values)
+    assert set(actual_values) == ref_unique_values

scripts/v.dissolve/v.dissolve.py

@@ -205,10 +205,6 @@ def check_aggregate_methods_or_fatal(methods, backend):
     # and open for SQLite depending on its extensions.
 
 
-# TODO: Confirm that there is only one record in the table
-# for a given attribute value after dissolve.
-
-
 def aggregate_attributes_sql(
     input_name,
     column,