show warning instead of error when passing bytes to iri_to_uri (#2709)

CHANGES.rst

@@ -10,6 +10,8 @@ Unreleased
 -   The debugger escapes the exception message in the page title. :pr:`2719`
 -   When binding ``routing.Map``, a long IDNA ``server_name`` with a port does not fail
     encoding. :issue:`2700`
+-   ``iri_to_uri`` shows a deprecation warning instead of an error when passing bytes.
+    :issue:`2708`
 
 
 Version 2.3.4

src/werkzeug/urls.py

@@ -966,6 +966,16 @@ def iri_to_uri(
 
     .. versionadded:: 0.6
     """
+    if charset is not None:
+        warnings.warn(
+            "The 'charset' parameter is deprecated and will be removed"
+            " in Werkzeug 3.0.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+    else:
+        charset = "utf-8"
+
     if isinstance(iri, tuple):
         warnings.warn(
             "Passing a tuple is deprecated and will not be supported in Werkzeug 3.0.",
@@ -982,16 +992,6 @@ def iri_to_uri(
         )
         iri = iri.decode(charset)
 
-    if charset is not None:
-        warnings.warn(
-            "The 'charset' parameter is deprecated and will be removed"
-            " in Werkzeug 3.0.",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-    else:
-        charset = "utf-8"
-
     if errors is not None:
         warnings.warn(
             "The 'errors' parameter is deprecated and will be removed in Werkzeug 3.0.",

tests/test_urls.py

@@ -229,6 +229,9 @@ def test_iri_support():
     with pytest.deprecated_call():
         assert urls.uri_to_iri(b"/foo") == "/foo"
 
+    with pytest.deprecated_call():
+        assert urls.iri_to_uri(b"/foo") == "/foo"
+
     assert urls.iri_to_uri("/foo") == "/foo"
 
     assert (