False positives with German mobile phone numbers

[tobiaseisenschenk]

Describe the bug
Mobile phone numbers in Germany start with a 0 prefix such as 0157xxxxxxx. However the preceding 0 is dropped if the country code prefix +49 is added. This is described on this wikipedia page. Therefore the related change made a while ago is not restrictive enough.

Examples
invalid:
'+49015123456789'
valid:
'+4915123456789'

Additional context
Validator.js version: 13.6.0
Node.js version: v12.15.0
OS platform: macOS

[profnandaa]

Thanks for raising. You are right, PR welcome!

[Burnett01]

Hey guys, I have submitted a PR #1675 for this issue, but the validation of german mobile phone numbers overall is still not correct.

I was wondering as to why a number such as 030556699884 is deemed a valid german mobile phone number.
The format of that number is only valid for landline phones and is subject to a state in Germany, Berlin.

According to Wikipedia and the federal agency of networking (Bundesnetzagentur), german mobile phone numbers always start with either +49|0 and 1, for example: 017699988855 (+4917699988855).

Numbers for mobile services commence with a two-digit service code. The service code is
followed by a subscriber number consisting of a block code and a terminal equipment
number. When dialling the number from a German landline or mobile number, the number
must be preceded by the prefix "0".
(Source)

The change introduced with #1378 (#1391) is invalid as it includes local (landline) phone numbers for Berlin as well, but those are not mobile phone numbers. (See #941)

Additonally, the change introduced with #933 is probably incorrect as well, as it would allow for german mobile phone numbers without a leading country code (+49) or zero (0). This only makes sense when the userland code explicitly offers two input fields where the first one already contains +49 or 0, and only the second one gets validated.

Example:

<input type="text" value="+49" readonly/> <input type="text" placeholder="Enter number" readonly/>

But then again, this is subject to userland and shouldn't be part of this library.

If it's of any help, I have created another branch called fix/improve-german-phone-validation in my fork where german mobile phone numbers are strictly validated (where the leading country code (+49) or 0 must be present and landlines are not included.).: Burnett01@a98ca0c

Greetings, Steve