Resolve edge case in nested BP Groups (#2592)

sanic/app.py

@@ -480,17 +480,16 @@ def blueprint(
             for item in blueprint:
                 params = {**options}
                 if isinstance(blueprint, BlueprintGroup):
-                    if blueprint.url_prefix:
-                        merge_from = [
-                            options.get("url_prefix", ""),
-                            blueprint.url_prefix,
-                        ]
-                        if not isinstance(item, BlueprintGroup):
-                            merge_from.append(item.url_prefix or "")
-                        merged_prefix = "/".join(
-                            u.strip("/") for u in merge_from
-                        ).rstrip("/")
-                        params["url_prefix"] = f"/{merged_prefix}"
+                    merge_from = [
+                        options.get("url_prefix", ""),
+                        blueprint.url_prefix or "",
+                    ]
+                    if not isinstance(item, BlueprintGroup):
+                        merge_from.append(item.url_prefix or "")
+                    merged_prefix = "/".join(
+                        u.strip("/") for u in merge_from if u
+                    ).rstrip("/")
+                    params["url_prefix"] = f"/{merged_prefix}"
 
                     for _attr in ["version", "strict_slashes"]:
                         if getattr(item, _attr) is None:

tests/test_blueprint_group.py

@@ -323,3 +323,20 @@ def blueprint_2_default_route(request):
     assert "api/v1/grouped/bp2/" in routes
     assert "api/v1/primary/grouped/bp1" in routes
     assert "api/v1/primary/grouped/bp2" in routes
+
+
+def test_nested_bp_group_properties():
+    one = Blueprint("one", url_prefix="/one")
+    two = Blueprint.group(one)
+    three = Blueprint.group(two, url_prefix="/three")
+
+    @one.route("/four")
+    def handler(request):
+        return text("pi")
+
+    app = Sanic("PropTest")
+    app.blueprint(three)
+    app.router.finalize()
+
+    routes = [route.path for route in app.router.routes]
+    assert routes == ["three/one/four"]