ePassport: render the MRZ personal number without its fillers

9303 Part 4, positions 29 to 42: "Any special characters, including spaces,
in the personal identification number ... shall be replaced by the filler
character (<). The number shall be followed by the filler character (<)
repeated up to position 42."

So the field holds two different kinds of filler.  The trailing run is
padding, which was already stripped, but a filler inside the number stands
for a space or special character substituted on the way in, and those were
printed as they came - a US passport showed its personal number with a '<'
in the middle of it.

Strip the padding, then put a space back for what remains.  It is the
closest recovery available: the original could have been a hyphen, and the
MRZ does not keep which.

optional_data itself stays a faithful copy of the field.  Nothing else
reads it, and it is the personal number that is being rendered here.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -3,7 +3,7 @@ All notable changes to this project will be documented in this file.
 This project uses the changelog in accordance with [keepchangelog](http://keepachangelog.com/). Please use this to write notable changes, which is not the same as git commit log...
 
 ## [unreleased][unreleased]
-- Fixed `tools/ePassport` - a document number longer than nine characters left its overflow in the MRZ optional-data field, where it was reported as the holder's personal number (@pkilar)
+- Fixed `tools/ePassport` - the personal number read from the MRZ optional-data field showed a filler character where a space belonged, and a document number longer than nine characters left its overflow there (@pkilar)
 - Added `tools/ePassport` - EF_DG13 is decoded, and a Polish document's PESEL is shown as the personal number when it carries no EF_DG11 (@pkilar)
 - Fixed `tools/ePassport` - a disabled button drew Kivy's banded disabled texture, which left its label unreadable (@pkilar)
 - Fixed `hf 14b` - a card asking for a waiting time extension of 4 or more left the timeout at zero, so any ISO14443-B card needing time to answer looked like it had stopped responding (@pkilar)

tools/ePassport/epassport/emrtd/model.py

@@ -10,7 +10,7 @@ from __future__ import annotations
 from dataclasses import dataclass, field
 from pathlib import Path
 
-from .mrz import Mrz
+from .mrz import FILLER, Mrz
 
 
 class FileState:
@@ -81,6 +81,17 @@ class DocumentDetails:
         return not any(v for k, v in vars(self).items() if not k.startswith("image_"))
 
 
+def _mrz_personal_number(field: str) -> str:
+    """The MRZ optional-data field read as a personal number.
+
+    9303 replaces every space and special character in the number with ``<``
+    and then pads the field with the same character, so the trailing run is
+    padding while a filler inside the number stood for something we cannot
+    recover.  A space is the closest we can put back.
+    """
+    return field.rstrip(FILLER).replace(FILLER, " ").strip()
+
+
 #: Poland carries the PESEL, its national identity number, in this DG13 tag.
 PESEL_TAG = "5F70"
 
@@ -232,7 +243,7 @@ class PassportRecord:
         if self.personal.personal_number:
             return self.personal.personal_number
         if self.mrz is not None:
-            optional = self.mrz.optional_data.value.strip()
+            optional = _mrz_personal_number(self.mrz.optional_data.value)
             if optional:
                 return optional
         if self.dg13_personal_number:
@@ -258,7 +269,7 @@ class PassportRecord:
         """Where :attr:`personal_number` came from, for an honest caption."""
         if self.personal.personal_number:
             return "DG11"
-        if self.mrz is not None and self.mrz.optional_data.value.strip():
+        if self.mrz is not None and _mrz_personal_number(self.mrz.optional_data.value):
             return "MRZ"
         if self.dg13_personal_number:
             return "DG13"

tools/ePassport/tests/test_personal_number.py

@@ -0,0 +1,53 @@
+"""The personal number taken from the MRZ optional-data field.
+
+ICAO 9303 Part 4, positions 29 to 42: "Any special characters, including
+spaces, in the personal identification number ... shall be replaced by the
+filler character (<). The number shall be followed by the filler character
+(<) repeated up to position 42."
+
+So the trailing run is padding, and a filler inside the number stands for a
+space or a special character that was substituted on the way in.  Printing it
+raw put a '<' in the middle of the number.
+"""
+
+from __future__ import annotations
+
+from epassport.emrtd.model import PassportRecord
+from epassport.emrtd.mrz import Checked, Mrz
+
+
+def _record(optional: str) -> PassportRecord:
+    record = PassportRecord()
+    blank = Checked("")
+    record.mrz = Mrz(
+        kind="TD3",
+        lines=[],
+        document_number=blank,
+        date_of_birth=blank,
+        date_of_expiry=blank,
+        composite=blank,
+        nationality="USA",
+        optional_data=Checked(optional),
+    )
+    return record
+
+
+def test_a_filler_inside_the_number_stands_for_a_space() -> None:
+    assert _record("123456789<0123").personal_number == "123456789 0123"
+
+
+def test_trailing_padding_never_reaches_the_value() -> None:
+    assert _record("ZE184226B").personal_number == "ZE184226B"
+    assert _record("ZE184226B<<<<<").personal_number == "ZE184226B"
+
+
+def test_a_plain_number_is_untouched() -> None:
+    assert _record("6512168").personal_number == "6512168"
+
+
+def test_an_empty_field_yields_no_number() -> None:
+    assert _record("").personal_number_source == ""
+
+
+def test_the_source_is_still_reported_as_the_mrz() -> None:
+    assert _record("123456789<0123").personal_number_source == "MRZ"