Fix minor holes in PEP-508 name validation

changes/1762.bugfix.rst

@@ -0,0 +1 @@
+When creating a new project, the validation for App Name now rejects all non-ASCII values.

src/briefcase/config.py

@@ -15,8 +15,12 @@
 from .constants import RESERVED_WORDS
 from .exceptions import BriefcaseConfigError
 
-# PEP508 provides a basic restriction on naming
-PEP508_NAME_RE = re.compile(r"^([A-Z0-9]|[A-Z0-9][A-Z0-9._-]*[A-Z0-9])$", re.IGNORECASE)
+# PEP 508 restricts the naming of modules. The PEP defines a regex that uses
+# re.IGNORECASE; but in in practice, packaging uses a version that rolls out the lower
+# case, which has very slightly different semantics with non-ASCII characters. This
+# definition is the one from
+# https://github.com/pypa/packaging/blob/24.0/src/packaging/_tokenizer.py#L80
+PEP508_NAME_RE = re.compile(r"^([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9._-]*[a-zA-Z0-9])$")
 
 
 def is_valid_pep508_name(app_name):

tests/commands/new/test_validate_app_name.py

@@ -10,7 +10,6 @@
         "42helloworld",  # ?? Are we sure this is correct?
         "hello_world",
         "hello-world",
-        "helloworld_ı",
     ],
 )
 def test_valid_app_name(new_command, name):

tests/config/test_is_valid_app_name.py

@@ -34,6 +34,12 @@ def test_is_valid_app_name(name):
         "main",
         "socket",
         "test",
+        # ı, İ and K (i.e. 0x212a) are valid ASCII when made lowercase and as such are
+        # accepted by the official PEP 508 regex... but they are rejected here to ensure
+        # compliance with the regex that is used in practice.
+        "helloworld_ı",
+        "İstanbul",
+        "Kelvin",
     ],
 )
 def test_is_invalid_app_name(name):