Several fixes for parsing display names

* Fix error message text for input addresses without @-signs. The incorrect message was "There must be something after the @-sign.". This was broken by the changes to parse display names. Prior to that, the message was "The email address is not valid. It must have exactly one @-sign.".
* Move the allow_display_name check to the end of the syntax checks. The optional checks should be the last to occur so that fatal syntax errors are raised first.
* Check that display name email addresses have a closing angle bracket and nothing after.
* Don't treat < + U+0338 (Combining Long Solidus Overlay) as the start of a bracketed email address. This would already be rejected because the combining character would be reported as an unsafe character at the start of the address, but it may be confusing since the caller won't see the address that way. When splitting the address into parts, skip the other special characters (@, quote, backslash) that have meaningful combining characters after them (i.e. they change under NFC normalization), although I don't think there are any such cases.

email_validator/syntax.py

@@ -48,12 +48,22 @@ def split_email(email: str) -> Tuple[Optional[str], str, str, bool]:
 
     def split_string_at_unquoted_special(text: str, specials: Tuple[str, ...]) -> Tuple[str, str]:
         # Split the string at the first character in specials (an @-sign
-        # or left angle bracket) that does not occur within quotes.
+        # or left angle bracket) that does not occur within quotes and
+        # is not followed by a Unicode combining character.
+        # If no special character is found, raise an error.
         inside_quote = False
         escaped = False
         left_part = ""
-        for c in text:
-            if inside_quote:
+        for i, c in enumerate(text):
+            # < plus U+0338 (Combining Long Solidus Overlay) normalizes to
+            # ≮ U+226E (Not Less-Than), and  it would be confusing to treat
+            # the < as the start of "<email>" syntax in that case. Liekwise,
+            # if anything combines with an @ or ", we should probably not
+            # treat it as a special character.
+            if unicodedata.normalize("NFC", text[i:])[0] != c:
+                left_part += c
+
+            elif inside_quote:
                 left_part += c
                 if c == '\\' and not escaped:
                     escaped = True
@@ -72,6 +82,9 @@ def split_string_at_unquoted_special(text: str, specials: Tuple[str, ...]) -> Tu
             else:
                 left_part += c
 
+        if len(left_part) == len(text):
+            raise EmailSyntaxError("An email address must have an @-sign.")
+
         # The right part is whatever is left.
         right_part = text[len(left_part):]
 
@@ -134,6 +147,14 @@ def unquote_quoted_string(text: str) -> Tuple[str, bool]:
         # Check for other unsafe characters.
         check_unsafe_chars(display_name, allow_space=True)
 
+        # Check that the right part ends with an angle bracket
+        # but allow spaces after it, I guess.
+        if ">" not in right_part:
+            raise EmailSyntaxError("An open angle bracket at the start of the email address has to be followed by a close angle bracket at the end.")
+        right_part = right_part.rstrip(" ")
+        if right_part[-1] != ">":
+            raise EmailSyntaxError("There can't be anything after the email address.")
+
         # Remove the initial and trailing angle brackets.
         addr_spec = right_part[1:].rstrip(">")
 

email_validator/validate_email.py

@@ -68,8 +68,6 @@ def validate_email(
     # part if the local part is quoted.
     display_name, local_part, domain_part, is_quoted_local_part \
         = split_email(email)
-    if display_name is not None and not allow_display_name:
-        raise EmailSyntaxError("A display name and angle brackets around the email address are not permitted here.")
 
     # Collect return values in this instance.
     ret = ValidatedEmail()
@@ -139,6 +137,11 @@ def validate_email(
     # Check the length of the address.
     validate_email_length(ret)
 
+    # Check that a display name is permitted. It's the last syntax check
+    # because we always check against optional parsing features last.
+    if display_name is not None and not allow_display_name:
+        raise EmailSyntaxError("A display name and angle brackets around the email address are not permitted here.")
+
     if check_deliverability and not test_environment:
         # Validate the email address's deliverability using DNS
         # and update the returned ValidatedEmail object with metadata.

tests/test_syntax.py

@@ -352,6 +352,7 @@ def test_domain_literal() -> None:
 @pytest.mark.parametrize(
     'email_input,error_msg',
     [
+        ('hello.world', 'An email address must have an @-sign.'),
         ('my@localhost', 'The part after the @-sign is not valid. It should have a period.'),
         ('[email protected]', 'An email address cannot have a period immediately after the @-sign.'),
         ('my@．leadingfwdot.com', 'An email address cannot have a period immediately after the @-sign.'),
@@ -413,6 +414,10 @@ def test_domain_literal() -> None:
         ('me@[untaggedtext]', 'The part after the @-sign in brackets is not an IPv4 address and has no address literal tag.'),
         ('me@[tag:invalid space]', 'The part after the @-sign contains invalid characters in brackets: SPACE.'),
         ('<[email protected]>', 'A display name and angle brackets around the email address are not permitted here.'),
+        ('<[email protected]', 'An open angle bracket at the start of the email address has to be followed by a close angle bracket at the end.'),
+        ('<[email protected]> !', 'There can\'t be anything after the email address.'),
+        ('<\u0338[email protected]', 'The email address contains invalid characters before the @-sign: \'<\'.'),
+        ('DisplayName <[email protected]>', 'An email address cannot have a hyphen immediately after the @-sign.'),
         ('DisplayName <[email protected]>', 'A display name and angle brackets around the email address are not permitted here.'),
         ('Display Name <[email protected]>', 'A display name and angle brackets around the email address are not permitted here.'),
         ('\"Display Name\" <[email protected]>', 'A display name and angle brackets around the email address are not permitted here.'),