feat(blueprints): 添加蓝图URL前缀动态计算功能

添加对嵌套蓝图URL前缀的动态计算支持，包括：
1. 将url_prefix改为属性并添加setter
2. 新增full_url_prefix属性获取完整前缀
3. 添加get_registered_url_prefix方法获取特定注册的前缀
4. 添加_registrations字典存储注册信息
5. 新增测试用例验证功能

src/flask/sansio/blueprints.py

@@ -199,7 +199,7 @@ class Blueprint(Scaffold):
             raise ValueError("'name' may not contain a dot '.' character.")
 
         self.name = name
-        self.url_prefix = url_prefix
+        self._url_prefix = url_prefix
         self.subdomain = subdomain
         self.deferred_functions: list[DeferredSetupFunction] = []
 
@@ -209,6 +209,57 @@ class Blueprint(Scaffold):
         self.url_values_defaults = url_defaults
         self.cli_group = cli_group
         self._blueprints: list[tuple[Blueprint, dict[str, t.Any]]] = []
+        self._registrations: dict[str, dict[str, t.Any]] = {}
+
+    @property
+    def url_prefix(self) -> str | None:
+        """The URL prefix for this blueprint as set during initialization.
+
+        To get the full URL prefix including parent blueprint prefixes after
+        registration, use :attr:`full_url_prefix` or
+        :meth:`get_registered_url_prefix`.
+
+        .. versionadded:: 0.7
+        """
+        return self._url_prefix
+
+    @url_prefix.setter
+    def url_prefix(self, value: str | None) -> None:
+        self._url_prefix = value
+
+    @property
+    def full_url_prefix(self) -> str | None:
+        """The full URL prefix for this blueprint including any parent blueprint
+        prefixes.
+
+        If the blueprint has been registered exactly once, returns the full
+        URL prefix. If the blueprint has not been registered or has been
+        registered multiple times, returns None.
+
+        To get the URL prefix for a specific registration when the blueprint
+        has been registered multiple times, use :meth:`get_registered_url_prefix`.
+
+        .. versionadded:: 3.1
+        """
+        if len(self._registrations) == 1:
+            return next(iter(self._registrations.values())).get("url_prefix")
+        return None
+
+    def get_registered_url_prefix(self, name: str | None = None) -> str | None:
+        """Get the full URL prefix for a specific registration of this blueprint.
+
+        :param name: The registration name. If not provided and the blueprint
+            has been registered exactly once, returns that registration's prefix.
+        :return: The full URL prefix for the registration, or None if not found.
+
+        .. versionadded:: 3.1
+        """
+        if name is None:
+            if len(self._registrations) == 1:
+                return next(iter(self._registrations.values())).get("url_prefix")
+            return None
+        registration = self._registrations.get(name)
+        return registration.get("url_prefix") if registration else None
 
     def _check_setup_finished(self, f_name: str) -> None:
         if self._got_registered_once:
@@ -320,6 +371,13 @@ class Blueprint(Scaffold):
         self._got_registered_once = True
         state = self.make_setup_state(app, options, first_bp_registration)
 
+        self._registrations[name] = {
+            "url_prefix": state.url_prefix,
+            "subdomain": state.subdomain,
+            "name": name,
+            "options": options.copy(),
+        }
+
         if self.has_static_folder:
             state.add_url_rule(
                 f"{self.static_url_path}/<path:filename>",

test_nested_blueprint_prefix.py

@@ -0,0 +1,180 @@
+"""Test cases for nested blueprint URL prefix dynamic calculation."""
+import pytest
+import flask
+
+
+def test_blueprint_url_prefix_original():
+    """Test that url_prefix returns the original value set during initialization."""
+    bp = flask.Blueprint("test", __name__, url_prefix="/test")
+
+    assert bp.url_prefix == "/test"
+    assert bp._url_prefix == "/test"
+
+
+def test_blueprint_full_url_prefix_before_registration():
+    """Test that full_url_prefix returns None before registration."""
+    bp = flask.Blueprint("test", __name__, url_prefix="/test")
+
+    assert bp.full_url_prefix is None
+
+
+def test_blueprint_full_url_prefix_after_single_registration():
+    """Test that full_url_prefix returns the full path after single registration."""
+    app = flask.Flask(__name__)
+    bp = flask.Blueprint("test", __name__, url_prefix="/test")
+
+    @bp.route("/")
+    def index():
+        return "test"
+
+    app.register_blueprint(bp, url_prefix="/api")
+
+    assert bp.url_prefix == "/test"
+    assert bp.full_url_prefix == "/api/test"
+    assert bp.get_registered_url_prefix() == "/api/test"
+
+
+def test_nested_blueprint_full_url_prefix():
+    """Test that nested blueprints get the full URL prefix including parent prefixes."""
+    app = flask.Flask(__name__)
+
+    parent = flask.Blueprint("parent", __name__, url_prefix="/parent")
+    child = flask.Blueprint("child", __name__, url_prefix="/child")
+    grandchild = flask.Blueprint("grandchild", __name__, url_prefix="/grandchild")
+
+    @parent.route("/")
+    def parent_index():
+        return "parent"
+
+    @child.route("/")
+    def child_index():
+        return "child"
+
+    @grandchild.route("/")
+    def grandchild_index():
+        return "grandchild"
+
+    child.register_blueprint(grandchild)
+    parent.register_blueprint(child)
+    app.register_blueprint(parent, url_prefix="/api")
+
+    assert parent.url_prefix == "/parent"
+    assert parent.full_url_prefix == "/api/parent"
+
+    assert child.url_prefix == "/child"
+    assert child.full_url_prefix == "/api/parent/child"
+
+    assert grandchild.url_prefix == "/grandchild"
+    assert grandchild.full_url_prefix == "/api/parent/child/grandchild"
+
+
+def test_nested_blueprint_url_rules():
+    """Test that nested blueprints have correct URL rules."""
+    app = flask.Flask(__name__)
+
+    parent = flask.Blueprint("parent", __name__, url_prefix="/parent")
+    child = flask.Blueprint("child", __name__, url_prefix="/child")
+
+    @parent.route("/home")
+    def parent_home():
+        return "parent home"
+
+    @child.route("/home")
+    def child_home():
+        return "child home"
+
+    parent.register_blueprint(child)
+    app.register_blueprint(parent, url_prefix="/api")
+
+    client = app.test_client()
+
+    assert client.get("/api/parent/home").data == b"parent home"
+    assert client.get("/api/parent/child/home").data == b"child home"
+
+
+def test_multiple_registrations():
+    """Test behavior when blueprint is registered multiple times."""
+    app = flask.Flask(__name__)
+    bp = flask.Blueprint("test", __name__, url_prefix="/test")
+
+    @bp.route("/")
+    def index():
+        return flask.request.endpoint
+
+    app.register_blueprint(bp, url_prefix="/api1")
+    app.register_blueprint(bp, name="test2", url_prefix="/api2")
+
+    assert bp.url_prefix == "/test"
+    assert bp.full_url_prefix is None
+    assert bp.get_registered_url_prefix() is None
+    assert bp.get_registered_url_prefix("test") == "/api1/test"
+    assert bp.get_registered_url_prefix("test2") == "/api2/test"
+
+    client = app.test_client()
+    assert client.get("/api1/test/").data == b"test.index"
+    assert client.get("/api2/test/").data == b"test2.index"
+
+
+def test_get_registered_url_prefix_with_name():
+    """Test get_registered_url_prefix with specific name."""
+    app = flask.Flask(__name__)
+    bp = flask.Blueprint("test", __name__, url_prefix="/test")
+
+    app.register_blueprint(bp, url_prefix="/api")
+
+    assert bp.get_registered_url_prefix("test") == "/api/test"
+    assert bp.get_registered_url_prefix("nonexistent") is None
+
+
+def test_blueprint_without_url_prefix():
+    """Test blueprint without initial url_prefix."""
+    app = flask.Flask(__name__)
+    bp = flask.Blueprint("test", __name__)
+
+    @bp.route("/")
+    def index():
+        return "test"
+
+    app.register_blueprint(bp, url_prefix="/api")
+
+    assert bp.url_prefix is None
+    assert bp.full_url_prefix == "/api"
+    assert bp.get_registered_url_prefix() == "/api"
+
+
+def test_nested_with_partial_prefixes():
+    """Test nested blueprints with some missing prefixes."""
+    app = flask.Flask(__name__)
+
+    parent = flask.Blueprint("parent", __name__)
+    child = flask.Blueprint("child", __name__, url_prefix="/child")
+    grandchild = flask.Blueprint("grandchild", __name__)
+
+    @parent.route("/")
+    def parent_index():
+        return "parent"
+
+    @child.route("/")
+    def child_index():
+        return "child"
+
+    @grandchild.route("/")
+    def grandchild_index():
+        return "grandchild"
+
+    child.register_blueprint(grandchild, url_prefix="/gc")
+    parent.register_blueprint(child)
+    app.register_blueprint(parent, url_prefix="/api")
+
+    assert parent.full_url_prefix == "/api"
+    assert child.full_url_prefix == "/api/child"
+    assert grandchild.full_url_prefix == "/api/child/gc"
+
+    client = app.test_client()
+    assert client.get("/api/").data == b"parent"
+    assert client.get("/api/child/").data == b"child"
+    assert client.get("/api/child/gc/").data == b"grandchild"
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])