FA-96516 / Phone number formatting / Open access
Dial string from E.164: spaced numbers are accepted as canonical · case 01
"+42 555..." produces a dial string that contains a space.
ROOT CAUSE
Only the leading plus is verified, not that the rest is digits.
THE FAILURE
Only the leading plus is verified, not that the rest is digits.
Unsuccessful approach: Ignoring spaces in the check still returns the spaced digits.
Case contract
Input [canonical +digits, caller country]. Toy table (code, exit prefix, trunk): DD 8/00/-, AA 42/00/0, BB 83/810/8, CC 891/011/-. The input must be "+" and digits only. The destination is the longest matching code. Same code as the caller: dial trunk + national number. Otherwise dial the caller exit prefix + code + national number. Unknown caller or code returns None.
Why this case matters
Click-to-call and PBX integrations dial the string produced here; a wrong prefix connects to a different subscriber or fails.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
e164, frm = x
TABLE = {'DD': ('8', '00', ''), 'AA': ('42', '00', '0'), 'BB': ('83', '810', '8'), 'CC': ('891', '011', '')}
if frm not in TABLE or not e164.startswith('+'):
return None
digits = e164[1:]
cc = max((v[0] for v in TABLE.values() if digits.startswith(v[0])), key=len, default=None)
if cc is None:
return None
nsn = digits[len(cc):]
own_cc, exit_prefix, trunk = TABLE[frm]
if cc == own_cc:
return trunk + nsn
return exit_prefix + cc + nsn
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['domestic call adds trunk', ['+42555011123', 'AA'], '0555011123'], ['domestic call without trunk', ['+8915550135', 'CC'], '5550135'], ['caller code is a prefix of destination code', ['+835550121221', 'DD'], '00835550121221'], ['destination code is a prefix of caller code', ['+8555010141', 'BB'], '8108555010141'], ['three-digit exit prefix', ['+8915550135', 'AA'], '008915550135'], ['spaced E.164 rejected', ['+42 555011123', 'AA'], None], ['missing plus rejected', ['42555011123', 'AA'], None], ['leading zero instead of plus rejected', ['042555011123', 'AA'], None], ['unknown caller country', ['+42555011123', 'ZZ'], None]], [['domestic call adds trunk', ['+42555012234', 'AA'], '0555012234'], ['domestic call without trunk', ['+8915550246', 'CC'], '5550246'], ['caller code is a prefix of destination code', ['+835550122332', 'DD'], '00835550122332'], ['destination code is a prefix of caller code', ['+8555010252', 'BB'], '8108555010252'], ['three-digit exit prefix', ['+8915550246', 'AA'], '008915550246'], ['spaced E.164 rejected', ['+42 555012234', 'AA'], None], ['missing plus rejected', ['42555012234', 'AA'], None], ['leading zero instead of plus rejected', ['042555012234', 'AA'], None], ['unknown caller country', ['+42555012234', 'ZZ'], None]], [['domestic call adds trunk', ['+42555013345', 'AA'], '0555013345'], ['domestic call without trunk', ['+8915550357', 'CC'], '5550357'], ['caller code is a prefix of destination code', ['+835550123443', 'DD'], '00835550123443'], ['destination code is a prefix of caller code', ['+8555010363', 'BB'], '8108555010363'], ['three-digit exit prefix', ['+8915550357', 'AA'], '008915550357'], ['spaced E.164 rejected', ['+42 555013345', 'AA'], None], ['missing plus rejected', ['42555013345', 'AA'], None], ['leading zero instead of plus rejected', ['042555013345', 'AA'], None], ['unknown caller country', ['+42555013345', 'ZZ'], None]], [['domestic call adds trunk', ['+42555014456', 'AA'], '0555014456'], ['domestic call without trunk', ['+8915550468', 'CC'], '5550468'], ['caller code is a prefix of destination code', ['+835550124554', 'DD'], '00835550124554'], ['destination code is a prefix of caller code', ['+8555010474', 'BB'], '8108555010474'], ['three-digit exit prefix', ['+8915550468', 'AA'], '008915550468'], ['spaced E.164 rejected', ['+42 555014456', 'AA'], None], ['missing plus rejected', ['42555014456', 'AA'], None], ['leading zero instead of plus rejected', ['042555014456', 'AA'], None], ['unknown caller country', ['+42555014456', 'ZZ'], None]], [['domestic call adds trunk', ['+42555015567', 'AA'], '0555015567'], ['domestic call without trunk', ['+8915550579', 'CC'], '5550579'], ['caller code is a prefix of destination code', ['+835550125665', 'DD'], '00835550125665'], ['destination code is a prefix of caller code', ['+8555010585', 'BB'], '8108555010585'], ['three-digit exit prefix', ['+8915550579', 'AA'], '008915550579'], ['spaced E.164 rejected', ['+42 555015567', 'AA'], None], ['missing plus rejected', ['42555015567', 'AA'], None], ['leading zero instead of plus rejected', ['042555015567', 'AA'], None], ['unknown caller country', ['+42555015567', 'ZZ'], None]]]
for label, arg, expected in fixtures[N - 1]:
check(label, solve(arg), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| domestic call adds trunk | 0555011123 | 0555011123 | Passed |
| domestic call without trunk | 5550135 | 5550135 | Passed |
| caller code is a prefix of destination code | 00835550121221 | 00835550121221 | Passed |
| destination code is a prefix of caller code | 8108555010141 | 8108555010141 | Passed |
| three-digit exit prefix | 008915550135 | 008915550135 | Passed |
| spaced E.164 rejected | 0 555011123 | None | Failed |
| missing plus rejected | None | None | Passed |
| leading zero instead of plus rejected | None | None | Passed |
| unknown caller country | None | None | Passed |
SHA-256 / 37fd84100e66b4c74d3cbe31d71fee3bad4da86c7716111b8916dac759c51f64
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
e164, frm = x
TABLE = {'DD': ('8', '00', ''), 'AA': ('42', '00', '0'), 'BB': ('83', '810', '8'), 'CC': ('891', '011', '')}
if frm not in TABLE or not e164.startswith('+') or not e164[1:].replace(' ', '').isdigit():
return None
digits = e164[1:]
cc = max((v[0] for v in TABLE.values() if digits.startswith(v[0])), key=len, default=None)
if cc is None:
return None
nsn = digits[len(cc):]
own_cc, exit_prefix, trunk = TABLE[frm]
if cc == own_cc:
return trunk + nsn
return exit_prefix + cc + nsn
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['domestic call adds trunk', ['+42555011123', 'AA'], '0555011123'], ['domestic call without trunk', ['+8915550135', 'CC'], '5550135'], ['caller code is a prefix of destination code', ['+835550121221', 'DD'], '00835550121221'], ['destination code is a prefix of caller code', ['+8555010141', 'BB'], '8108555010141'], ['three-digit exit prefix', ['+8915550135', 'AA'], '008915550135'], ['spaced E.164 rejected', ['+42 555011123', 'AA'], None], ['missing plus rejected', ['42555011123', 'AA'], None], ['leading zero instead of plus rejected', ['042555011123', 'AA'], None], ['unknown caller country', ['+42555011123', 'ZZ'], None]], [['domestic call adds trunk', ['+42555012234', 'AA'], '0555012234'], ['domestic call without trunk', ['+8915550246', 'CC'], '5550246'], ['caller code is a prefix of destination code', ['+835550122332', 'DD'], '00835550122332'], ['destination code is a prefix of caller code', ['+8555010252', 'BB'], '8108555010252'], ['three-digit exit prefix', ['+8915550246', 'AA'], '008915550246'], ['spaced E.164 rejected', ['+42 555012234', 'AA'], None], ['missing plus rejected', ['42555012234', 'AA'], None], ['leading zero instead of plus rejected', ['042555012234', 'AA'], None], ['unknown caller country', ['+42555012234', 'ZZ'], None]], [['domestic call adds trunk', ['+42555013345', 'AA'], '0555013345'], ['domestic call without trunk', ['+8915550357', 'CC'], '5550357'], ['caller code is a prefix of destination code', ['+835550123443', 'DD'], '00835550123443'], ['destination code is a prefix of caller code', ['+8555010363', 'BB'], '8108555010363'], ['three-digit exit prefix', ['+8915550357', 'AA'], '008915550357'], ['spaced E.164 rejected', ['+42 555013345', 'AA'], None], ['missing plus rejected', ['42555013345', 'AA'], None], ['leading zero instead of plus rejected', ['042555013345', 'AA'], None], ['unknown caller country', ['+42555013345', 'ZZ'], None]], [['domestic call adds trunk', ['+42555014456', 'AA'], '0555014456'], ['domestic call without trunk', ['+8915550468', 'CC'], '5550468'], ['caller code is a prefix of destination code', ['+835550124554', 'DD'], '00835550124554'], ['destination code is a prefix of caller code', ['+8555010474', 'BB'], '8108555010474'], ['three-digit exit prefix', ['+8915550468', 'AA'], '008915550468'], ['spaced E.164 rejected', ['+42 555014456', 'AA'], None], ['missing plus rejected', ['42555014456', 'AA'], None], ['leading zero instead of plus rejected', ['042555014456', 'AA'], None], ['unknown caller country', ['+42555014456', 'ZZ'], None]], [['domestic call adds trunk', ['+42555015567', 'AA'], '0555015567'], ['domestic call without trunk', ['+8915550579', 'CC'], '5550579'], ['caller code is a prefix of destination code', ['+835550125665', 'DD'], '00835550125665'], ['destination code is a prefix of caller code', ['+8555010585', 'BB'], '8108555010585'], ['three-digit exit prefix', ['+8915550579', 'AA'], '008915550579'], ['spaced E.164 rejected', ['+42 555015567', 'AA'], None], ['missing plus rejected', ['42555015567', 'AA'], None], ['leading zero instead of plus rejected', ['042555015567', 'AA'], None], ['unknown caller country', ['+42555015567', 'ZZ'], None]]]
for label, arg, expected in fixtures[N - 1]:
check(label, solve(arg), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| domestic call adds trunk | 0555011123 | 0555011123 | Passed |
| domestic call without trunk | 5550135 | 5550135 | Passed |
| caller code is a prefix of destination code | 00835550121221 | 00835550121221 | Passed |
| destination code is a prefix of caller code | 8108555010141 | 8108555010141 | Passed |
| three-digit exit prefix | 008915550135 | 008915550135 | Passed |
| spaced E.164 rejected | 0 555011123 | None | Failed |
| missing plus rejected | None | None | Passed |
| leading zero instead of plus rejected | None | None | Passed |
| unknown caller country | None | None | Passed |
SHA-256 / 70459ea88f1f61ec749f4285d675ece6eecf3b49acc6e2fa8cc0968f6a3cd516
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 9 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.
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Sign in to the archive ↗Verification & scope
A deterministic toy contract over synthetic, obviously fictitious telephone numbers and toy country tables. The rules are stipulated for this model only and make no claim of conformance with any numbering plan or telecommunications standard. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.
Observations recorded using Python 3.12.14 at 2026-09-29T14:52:23.488569+00:00.
Case digest / e4dfbe9ccaae320fc3580ac848dce158e55c26c1974c84928a9e275a99b65b1f