"first_null_row" configuration option

internal/project/project_test.go

@@ -191,6 +191,34 @@ topdata:
 	}
 }
 
+func TestEffectiveConfigIncludesTopDataRowGeneration(t *testing.T) {
+	root := t.TempDir()
+	writeProjectFile(t, filepath.Join(root, ConfigFile), `
+module:
+  name: Test Module
+  resref: testmod
+topdata:
+  source: topdata
+  row_generation:
+    - namespace: portraits
+      mode: first_null_row
+`)
+
+	proj, err := Load(root)
+	if err != nil {
+		t.Fatalf("Load returned error: %v", err)
+	}
+
+	rules := proj.EffectiveConfig().TopData.RowGeneration
+	if len(rules) != 1 {
+		t.Fatalf("expected one topdata row generation rule, got %#v", rules)
+	}
+	got := rules[0]
+	if got.Dataset != "portraits" || got.Namespace != "portraits" || got.Mode != "first_null_row" {
+		t.Fatalf("unexpected topdata row generation rule: %#v", got)
+	}
+}
+
 func TestEffectiveConfigIncludesTopDataClassFeatInjections(t *testing.T) {
 	root := t.TempDir()
 	writeProjectFile(t, filepath.Join(root, ConfigFile), `
@@ -252,6 +280,12 @@ func TestValidateLayoutRejectsInvalidTopDataValueEncodings(t *testing.T) {
 					{Dataset: "racialtypes/core", Column: "ECL", Value: 1},
 					{Dataset: "", Column: "", Value: 0},
 				},
+				RowGeneration: []TopDataRowGenerationConfig{
+					{Dataset: "portraits", Mode: "first_null_row"},
+					{Dataset: "portraits", Mode: "after_base"},
+					{Namespace: "placeabletypes", Mode: "unsupported"},
+					{Mode: "first_null_row"},
+				},
 			},
 		},
 	}
@@ -271,6 +305,9 @@ func TestValidateLayoutRejectsInvalidTopDataValueEncodings(t *testing.T) {
 		"topdata.value_defaults[1] duplicates an earlier dataset/column default",
 		"topdata.value_defaults[2].dataset is required",
 		"topdata.value_defaults[2].column is required",
+		"topdata.row_generation[1] duplicates an earlier dataset row generation rule",
+		"topdata.row_generation[2].mode \"unsupported\" is not supported",
+		"topdata.row_generation[3].dataset is required",
 	} {
 		if !strings.Contains(text, want) {
 			t.Fatalf("expected validation error %q, got %v", want, err)