Test email address validation with esoteric email addresses

gistfile1.m

- (BOOL)isValidEmailAddress:(NSString *)text {
    NSError *error = NULL;
    NSRange textRange = {0, [text length]};
    NSDataDetector *detector = [NSDataDetector dataDetectorWithTypes:NSTextCheckingTypeLink error:&error];
    if (!detector) {
        NSLog(@"Could not instantiate link detector for email validation: %@", error);
        return NO;
    }
    
    NSTextCheckingResult *result = [detector firstMatchInString:text options:0 range:textRange];
    if (![result.URL.scheme isEqual:@"mailto"]) {
        // No link was detected, or it wasn't an email address
        return NO;
    }
    if (result.range.location > textRange.location || result.range.length < textRange.length) {
        // The detected email address does't span the entire input text
        return NO;
    }
    
    return YES;
}

- (void)testEmail:(NSString *)text isValid:(BOOL)isValid {
    BOOL result = [self isValidEmailAddress:text];
    if (result != isValid) NSLog(@"%@ should be %@", text, isValid ? @"valid" : @"invalid");
}

- (void)testEmails {
    [self testEmail:@"NotAnEmail" isValid:NO];
    [self testEmail:@"@NotAnEmail" isValid:NO];
    [self testEmail:@"\"test\\\\blah\"@example.com" isValid:YES];
    [self testEmail:@"\"test\\blah\"@example.com" isValid:NO];
    [self testEmail:@"\"test\\\rblah\"@example.com" isValid:YES];
    [self testEmail:@"\"test\rblah\"@example.com" isValid:NO];
    [self testEmail:@"\"test\\\"blah\"@example.com" isValid:YES];
    [self testEmail:@"\"test\"blah\"@example.com" isValid:NO];
    [self testEmail:@"customer/department@example.com" isValid:YES];
    [self testEmail:@"$A12345@example.com" isValid:YES];
    [self testEmail:@"!def!xyz%abc@example.com" isValid:YES];
    [self testEmail:@"_Yosemite.Sam@example.com" isValid:YES];
    [self testEmail:@"~@example.com" isValid:YES];
    [self testEmail:@".wooly@example.com" isValid:NO];
    [self testEmail:@"wo..oly@example.com" isValid:NO];
    [self testEmail:@"pootietang.@example.com" isValid:NO];
    [self testEmail:@".@example.com" isValid:NO];
    [self testEmail:@"\"Austin@Powers\"@example.com" isValid:YES];
    [self testEmail:@"Ima.Fool@example.com" isValid:YES];
    [self testEmail:@"\"Ima.Fool\"@example.com" isValid:YES];
    [self testEmail:@"\"Ima Fool\"@example.com" isValid:YES];
    [self testEmail:@"Ima Fool@example.com" isValid:NO];
}

Results:

✅ NotAnEmail detected as invalid
✅ @NotAnEmail detected as invalid
⛔️ "test\\blah"@example.com should be valid
✅ "test\blah"@example.com detected as invalid
⛔️ "test\\nblah"@example.com should be valid
✅ "test\nblah"@example.com detected as invalid
⛔️ "test\"blah"@example.com should be valid
✅ "test"blah"@example.com detected as invalid
✅ customer/department@example.com detected as valid
⛔️ $A12345@example.com should be valid
⛔️ !def!xyz%abc@example.com should be valid
⛔️ _Yosemite.Sam@example.com should be valid
⛔️ ~@example.com should be valid
✅ .wooly@example.com detected as invalid
⛔️ wo..oly@example.com should be invalid
✅ pootietang.@example.com detected as invalid
✅ .@example.com detected as invalid
⛔️ "Austin@Powers"@example.com should be valid
✅ Ima.Fool@example.com detected as valid
⛔️ "Ima.Fool"@example.com should be valid
⛔️ "Ima Fool"@example.com should be valid
✅ Ima Fool@example.com detected as invalid

11 of 22 failed.