Code Refactor

I have changed code across several files to be more Pythonic, readable and succinct.

src/flask/app.py

@@ -9,6 +9,7 @@ import weakref
 from collections.abc import Iterator as _abc_Iterator
 from datetime import timedelta
 from itertools import chain
+from itertools import product
 from threading import Lock
 from types import TracebackType
 
@@ -823,9 +824,7 @@ class Flask(Scaffold):
 
         .. versionadded:: 0.8
         """
-        root_path = self.root_path
+        root_path = self.instance_path if instance_relative else self.root_path
-        if instance_relative:
-            root_path = self.instance_path
         defaults = dict(self.default_config)
         defaults["ENV"] = os.environ.get("FLASK_ENV") or "production"
         defaults["DEBUG"] = get_debug_flag()
@@ -994,7 +993,7 @@ class Flask(Scaffold):
         for name in names:
             if name in self.template_context_processors:
                 for func in self.template_context_processors[name]:
-                    context.update(func())
+                    context |= func()
 
         context.update(orig_ctx)
 
@@ -1007,7 +1006,7 @@ class Flask(Scaffold):
         """
         rv = {"app": self, "g": g}
         for processor in self.shell_context_processors:
-            rv.update(processor())
+            rv |= processor()
         return rv
 
     @property
@@ -1167,11 +1166,7 @@ class Flask(Scaffold):
             sn_host, _, sn_port = server_name.partition(":")
 
         if not host:
-            if sn_host:
+            host = sn_host or "127.0.0.1"
-                host = sn_host
-            else:
-                host = "127.0.0.1"
-
         if port or port == 0:
             port = int(port)
         elif sn_port:
@@ -1559,8 +1554,7 @@ class Flask(Scaffold):
         exc_class, code = self._get_exc_class_and_code(type(e))
         names = (*request.blueprints, None)
 
-        for c in (code, None) if code is not None else (None,):
+        for c, name in product((code, None) if code is not None else (None,), names):
-            for name in names:
             handler_map = self.error_handler_spec[name][c]
 
             if not handler_map:
@@ -1604,9 +1598,7 @@ class Flask(Scaffold):
             return e
 
         handler = self._find_error_handler(e)
-        if handler is None:
+        return e if handler is None else self.ensure_sync(handler)(e)
-            return e
-        return self.ensure_sync(handler)(e)
 
     def trap_http_exception(self, e: Exception) -> bool:
         """Checks if an HTTP exception should be trapped or not.  By default
@@ -1638,10 +1630,7 @@ class Flask(Scaffold):
         ):
             return True
 
-        if trap_bad_request:
+        return isinstance(e, BadRequest) if trap_bad_request else False
-            return isinstance(e, BadRequest)
-
-        return False
 
     def handle_user_exception(
         self, e: Exception
@@ -1795,7 +1784,8 @@ class Flask(Scaffold):
         ):
             return self.make_default_options_response()
         # otherwise dispatch to the handler for that endpoint
-        view_args: t.Dict[str, t.Any] = req.view_args  # type: ignore[assignment]
+        # type: ignore[assignment]
+        view_args: t.Dict[str, t.Any] = req.view_args
         return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
 
     def full_dispatch_request(self) -> Response:
@@ -1886,10 +1876,7 @@ class Flask(Scaffold):
 
         .. versionadded:: 2.0
         """
-        if iscoroutinefunction(func):
+        return self.async_to_sync(func) if iscoroutinefunction(func) else func
-            return self.async_to_sync(func)
-
-        return func
 
     def async_to_sync(
         self, func: t.Callable[..., t.Coroutine]
@@ -2142,7 +2129,7 @@ class Flask(Scaffold):
 
         # make sure the body is an instance of the response class
         if not isinstance(rv, self.response_class):
-            if isinstance(rv, (str, bytes, bytearray)) or isinstance(rv, _abc_Iterator):
+            if isinstance(rv, (str, bytes, bytearray, _abc_Iterator)):
                 # let the response class set the status and headers instead of
                 # waiting to do it manually, so that the class can handle any
                 # special logic
@@ -2213,11 +2200,11 @@ class Flask(Scaffold):
             # If subdomain matching is disabled (the default), use the
             # default subdomain in all cases. This should be the default
             # in Werkzeug but it currently does not have that feature.
-            if not self.subdomain_matching:
+            subdomain = (
-                subdomain = self.url_map.default_subdomain or None
+                None
-            else:
+                if self.subdomain_matching
-                subdomain = None
+                else self.url_map.default_subdomain or None
-
+            )
             return self.url_map.bind_to_environ(
                 request.environ,
                 server_name=self.config["SERVER_NAME"],

src/flask/blueprints.py

@@ -84,7 +84,7 @@ class BlueprintSetupState:
         #: A dictionary with URL defaults that is added to each and every
         #: URL that was defined with the blueprint.
         self.url_defaults = dict(self.blueprint.url_values_defaults)
-        self.url_defaults.update(self.options.get("url_defaults", ()))
+        self.url_defaults |= self.options.get("url_defaults", ())
 
     def add_url_rule(
         self,
@@ -387,7 +387,7 @@ class Blueprint(Scaffold):
                 f" provide a unique name."
             )
 
-        first_bp_registration = not any(bp is self for bp in app.blueprints.values())
+        first_bp_registration = all(bp is not self for bp in app.blueprints.values())
         first_name_registration = name not in app.blueprints
 
         app.blueprints[name] = self
@@ -414,9 +414,7 @@ class Blueprint(Scaffold):
                 value = defaultdict(
                     dict,
                     {
-                        code: {
+                        code: dict(code_values.items())
-                            exc_class: func for exc_class, func in code_values.items()
-                        }
                         for code, code_values in value.items()
                     },
                 )

src/flask/cli.py

@@ -299,11 +299,8 @@ class ScriptInfo:
 
         if self.create_app is not None:
             app = self.create_app()
-        else:
+        elif self.app_import_path:
-            if self.app_import_path:
+            path, name = (re.split(r":(?![\\/])", self.app_import_path, 1) + [None])[:2]
-                path, name = (
-                    re.split(r":(?![\\/])", self.app_import_path, 1) + [None]
-                )[:2]
             import_name = prepare_import(path)
             app = locate_app(import_name, name)
         else:
@@ -797,13 +794,13 @@ def _validate_key(ctx, param, value):
                 'When "--cert" is an SSLContext object, "--key is not used.', ctx, param
             )
 
-        if not cert:
+        if cert:
-            raise click.BadParameter('"--cert" must also be specified.', ctx, param)
-
             ctx.params["cert"] = cert, value
 
         else:
-        if cert and not (is_adhoc or is_context):
+            raise click.BadParameter('"--cert" must also be specified.', ctx, param)
+
+    elif cert and not is_adhoc and not is_context:
         raise click.BadParameter('Required when using "--cert".', ctx, param)
 
     return value
@@ -962,7 +959,7 @@ def shell_command() -> None:
         with open(startup) as f:
             eval(compile(f.read(), startup, "exec"), ctx)
 
-    ctx.update(current_app.make_shell_context())
+    ctx |= current_app.make_shell_context()
 
     # Site, customize, or startup script can set a hook to call when
     # entering interactive mode. The default one sets up readline with
@@ -1008,7 +1005,7 @@ def routes_command(sort: str, all_methods: bool) -> None:
 
     ignored_methods = set(() if all_methods else ("HEAD", "OPTIONS"))
 
-    if sort in ("endpoint", "rule"):
+    if sort in {"endpoint", "rule"}:
         rules = sorted(rules, key=attrgetter(sort))
     elif sort == "methods":
         rules = sorted(rules, key=lambda rule: sorted(rule.methods))  # type: ignore

src/flask/config.py

@@ -1,3 +1,4 @@
+import contextlib
 import errno
 import json
 import os
@@ -133,12 +134,8 @@ class Config(dict):
 
             value = os.environ[key]
 
-            try:
+            with contextlib.suppress(Exception):
                 value = loads(value)
-            except Exception:
-                # Keep the value as a string if loading failed.
-                pass
-
             # Change to key.removeprefix(prefix) on Python >= 3.9.
             key = key[len_prefix:]
 
@@ -325,10 +322,7 @@ class Config(dict):
         for k, v in self.items():
             if not k.startswith(namespace):
                 continue
-            if trim_namespace:
+            key = k[len(namespace) :] if trim_namespace else k
-                key = k[len(namespace) :]
-            else:
-                key = k
             if lowercase:
                 key = key.lower()
             rv[key] = v

src/flask/debughelpers.py

@@ -129,9 +129,7 @@ def explain_template_loading_attempts(app: Flask, template, attempts) -> None:
 
         info.append(f"{idx + 1:5}: trying loader of {src_info}")
 
-        for line in _dump_loader_info(loader):
+        info.extend(f"       {line}" for line in _dump_loader_info(loader))
-            info.append(f"       {line}")
-
         if triple is None:
             detail = "no match"
         else:

src/flask/sessions.py

@@ -28,7 +28,7 @@ class SessionMixin(MutableMapping):
 
     @permanent.setter
     def permanent(self, value: bool) -> None:
-        self["_permanent"] = bool(value)
+        self["_permanent"] = value
 
     #: Some implementations can detect whether a session is newly
     #: created, but that is not guaranteed. Use with caution. The mixin
@@ -195,7 +195,7 @@ class SessionInterface:
         # set explicitly, or cached from SERVER_NAME detection
         # if False, return None
         if rv is not None:
-            return rv if rv else None
+            return rv or None
 
         rv = app.config["SERVER_NAME"]
 

src/flask/wrappers.py

@@ -52,10 +52,7 @@ class Request(RequestBase):
     @property
     def max_content_length(self) -> t.Optional[int]:  # type: ignore
         """Read-only view of the ``MAX_CONTENT_LENGTH`` config key."""
-        if current_app:
+        return current_app.config["MAX_CONTENT_LENGTH"] if current_app else None
-            return current_app.config["MAX_CONTENT_LENGTH"]
-        else:
-            return None
 
     @property
     def endpoint(self) -> t.Optional[str]:
@@ -67,10 +64,7 @@ class Request(RequestBase):
         This in combination with :attr:`view_args` can be used to
         reconstruct the same URL or a modified URL.
         """
-        if self.url_rule is not None:
+        return self.url_rule.endpoint if self.url_rule is not None else None
-            return self.url_rule.endpoint
-
-        return None
 
     @property
     def blueprint(self) -> t.Optional[str]:
@@ -103,10 +97,7 @@ class Request(RequestBase):
         """
         name = self.blueprint
 
-        if name is None:
+        return [] if name is None else _split_blueprint_path(name)
-            return []
-
-        return _split_blueprint_path(name)
 
     def _load_form_data(self) -> None:
         super()._load_form_data()