Bug in parsing passport with only one name

[tahajahangir]

Some passports (TD3 MRZ) have only one name, like:

P<IND<<AHMADI<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
K2578285<7IND5601240F2202288<<<<<<<<<<<<<<<4

or

P<PAKZAHRA<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
DD51243520PAK8501019F27032135440067474356<98

TD3CodeChecker(value) for this input fails with this exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "lib/python3.7/site-packages/mrz/checker/td3.py", line 123, in __init__
    self.result = self._all_hashes() & self._all_fields()
  File "lib/python3.7/site-packages/mrz/checker/_fields.py", line 223, in _all_fields
    self.optional_data &
  File "lib/python3.7/site-packages/mrz/checker/_fields.py", line 92, in identifier
    if check.begin_by(primary, "<") or check.begin_by(secondary, "<"):
  File "lib/python3.7/site-packages/mrz/base/string_checkers.py", line 119, in begin_by
    if string[0] != char:
IndexError: string index out of range

[Arg0s1080]

Yes, it's correct. That should not happen.

As ICAO 9303-3 3.4 says:
"The name of the holder is usually represented in two parts, the primary identifier and the secondary identifier."

So I think that the right thing to do, in case of getting only one identifier, would be to report it as a warning.

Also, thanks to your report, I discovered that something similar happens in mrz.generator. When the primary identifier is not given, an incorrect output is got. For example:

from mrz.generator.td3 import TD3CodeGenerator

print(TD3CodeGenerator("P",           # Document type
                       "Utopia",      # Country
                       "",            # Surname(s)
                       "Anna María",  # Given name(s)
                       "L898902C3",   # Passport number
                       "UTO",         # Nationality
                       "740812",      # Birth date
                       "F",           # Genre
                       "120415",      # Expiry date
                       "ZE184226B"))  # Id number

This wrong output is got:

P<UTO<<ANNA<MARIA<<<<<<<<<<<<<<<<<<<<<<<<<<<
L898902C36UTO7408122F1204159ZE184226B<<<<<10

Next week I'll work to try to fix it

Thank you very much for your feedback

[tahajahangir]

Thanks,
Also, the first example MRZ, is an instance of another false-positive, where optional data hash fails when optional-data is empty (all <) and optional-data-hash is < (instead of 0). I think it may be an error according to specs, but exists in real-world.

[Arg0s1080]

@tahajahangir , hi again!

_fields method at the beginning was very simple... then, little by little, I added more checks. That's why it had several errors. I almost rewritten it from scratch. I've tested it again and I think it works fine now, but if you find something wrong, I would appreciate it if you told me

Thank you so much!

PS: I have created a new issue with the 2nd problem you have reported.