FA-28656 / HTTP redirects / Open access
Expand redirect templates with context-specific escaping and missing-variable policy: missing capture explicit · case 01
Expand redirect templates with context-specific escaping and missing-variable policy: the missing capture explicit branch emits an incorrect decision.
ROOT CAUSE
The missing-capture-explicit decision uses 'index > len(captures)'; this violates the stipulated controller policy.
THE FAILURE
The missing-capture-explicit decision uses 'index > len(captures)'; this violates the stipulated controller policy.
Unsuccessful approach: The partial repair uses 'not captures' and still fails an explicit boundary or control.
Case contract
Expand redirect templates with context-specific escaping and missing-variable policy. The explicit fixture inputs and outputs define a bounded offline policy; request identity must accompany the decision.
Why this case matters
Models a redirect controller decision before following a target or exposing a redirect result.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
from urllib.parse import urlsplit, unquote, quote
import posixpath
import re
N = 1
observations = []
def solve(request, template, value, captures, index, query_value, literal):
return {'request': request, 'decision': [quote(value,safe=''), template.replace('{id}',value), captures[index] if 0<=index<len(captures) else None, index > len(captures), quote(query_value,safe=''), literal, bool(re.search(r'\{[^{}]+\}',template.replace('{id}',value))), captures[index] == '' if 0<=index<len(captures) else False, len(value.encode('utf-8')), template.count('{id}')]}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', '/item/{id}', 'a/b', ['zero', 'one'], 1, 'a&b', '{id}'), {'request': '/requests/' + str(N) + '/0', 'decision': ['a%2Fb', '/item/a/b', 'one', False, 'a%26b', '{id}', False, False, 3, 1]})
check('fixture 2', solve('/requests/' + str(N) + '/1', '/{id}/{id}', 'x y', ['only'], 0, 'a+b', 'plain'), {'request': '/requests/' + str(N) + '/1', 'decision': ['x%20y', '/x y/x y', 'only', False, 'a%2Bb', 'plain', False, False, 3, 2]})
check('fixture 3', solve('/requests/' + str(N) + '/2', '/fixed', 'z', [], 0, '', '{missing}'), {'request': '/requests/' + str(N) + '/2', 'decision': ['z', '/fixed', None, True, '', '{missing}', False, False, 1, 0]})
check('fixture 4', solve('/requests/' + str(N) + '/3', '/{id}', '%2F', ['a', 'b', 'c'], 2, 'x=y', '{id}'), {'request': '/requests/' + str(N) + '/3', 'decision': ['%252F', '/%2F', 'c', False, 'x%3Dy', '{id}', False, False, 3, 1]})
check('fixture 5', solve('/requests/' + str(N) + '/4', '/{id}', 'café', ['a'], 2, 'a b', '{{id}}'), {'request': '/requests/' + str(N) + '/4', 'decision': ['caf%C3%A9', '/café', None, True, 'a%20b', '{{id}}', False, False, 5, 1]})
check('fixture 6', solve('/requests/' + str(N) + '/5', '/{id}', '', [''], 0, '#frag', ''), {'request': '/requests/' + str(N) + '/5', 'decision': ['', '/', '', False, '%23frag', '', False, True, 0, 1]})
check('fixture 7', solve('/requests/' + str(N) + '/6', '/{other}/{id}', '/a//b', ['x'], 0, 'a/b', 'literal'), {'request': '/requests/' + str(N) + '/6', 'decision': ['%2Fa%2F%2Fb', '/{other}//a//b', 'x', False, 'a%2Fb', 'literal', True, False, 5, 1]})
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 |
|---|---|---|---|
| fixture 1 | {'decision': ['a%2Fb', '/item/a/b', 'one', False, 'a%26b', '{id}', False, False, 3, 1], 'request': '/requests/1/0'} | {'decision': ['a%2Fb', '/item/a/b', 'one', False, 'a%26b', '{id}', False, False, 3, 1], 'request': '/requests/1/0'} | Passed |
| fixture 2 | {'decision': ['x%20y', '/x y/x y', 'only', False, 'a%2Bb', 'plain', False, False, 3, 2], 'request': '/requests/1/1'} | {'decision': ['x%20y', '/x y/x y', 'only', False, 'a%2Bb', 'plain', False, False, 3, 2], 'request': '/requests/1/1'} | Passed |
| fixture 3 | {'decision': ['z', '/fixed', None, False, '', '{missing}', False, False, 1, 0], 'request': '/requests/1/2'} | {'decision': ['z', '/fixed', None, True, '', '{missing}', False, False, 1, 0], 'request': '/requests/1/2'} | Failed |
| fixture 4 | {'decision': ['%252F', '/%2F', 'c', False, 'x%3Dy', '{id}', False, False, 3, 1], 'request': '/requests/1/3'} | {'decision': ['%252F', '/%2F', 'c', False, 'x%3Dy', '{id}', False, False, 3, 1], 'request': '/requests/1/3'} | Passed |
| fixture 5 | {'decision': ['caf%C3%A9', '/café', None, True, 'a%20b', '{{id}}', False, False, 5, 1], 'request': '/requests/1/4'} | {'decision': ['caf%C3%A9', '/café', None, True, 'a%20b', '{{id}}', False, False, 5, 1], 'request': '/requests/1/4'} | Passed |
| fixture 6 | {'decision': ['', '/', '', False, '%23frag', '', False, True, 0, 1], 'request': '/requests/1/5'} | {'decision': ['', '/', '', False, '%23frag', '', False, True, 0, 1], 'request': '/requests/1/5'} | Passed |
| fixture 7 | {'decision': ['%2Fa%2F%2Fb', '/{other}//a//b', 'x', False, 'a%2Fb', 'literal', True, False, 5, 1], 'request': '/requests/1/6'} | {'decision': ['%2Fa%2F%2Fb', '/{other}//a//b', 'x', False, 'a%2Fb', 'literal', True, False, 5, 1], 'request': '/requests/1/6'} | Passed |
SHA-256 / 8ef1b375492c2f48e020119988247ad03db71daad0c788c34dfb746d59e59c70
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
from urllib.parse import urlsplit, unquote, quote
import posixpath
import re
N = 1
observations = []
def solve(request, template, value, captures, index, query_value, literal):
return {'request': request, 'decision': [quote(value,safe=''), template.replace('{id}',value), captures[index] if 0<=index<len(captures) else None, not captures, quote(query_value,safe=''), literal, bool(re.search(r'\{[^{}]+\}',template.replace('{id}',value))), captures[index] == '' if 0<=index<len(captures) else False, len(value.encode('utf-8')), template.count('{id}')]}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', '/item/{id}', 'a/b', ['zero', 'one'], 1, 'a&b', '{id}'), {'request': '/requests/' + str(N) + '/0', 'decision': ['a%2Fb', '/item/a/b', 'one', False, 'a%26b', '{id}', False, False, 3, 1]})
check('fixture 2', solve('/requests/' + str(N) + '/1', '/{id}/{id}', 'x y', ['only'], 0, 'a+b', 'plain'), {'request': '/requests/' + str(N) + '/1', 'decision': ['x%20y', '/x y/x y', 'only', False, 'a%2Bb', 'plain', False, False, 3, 2]})
check('fixture 3', solve('/requests/' + str(N) + '/2', '/fixed', 'z', [], 0, '', '{missing}'), {'request': '/requests/' + str(N) + '/2', 'decision': ['z', '/fixed', None, True, '', '{missing}', False, False, 1, 0]})
check('fixture 4', solve('/requests/' + str(N) + '/3', '/{id}', '%2F', ['a', 'b', 'c'], 2, 'x=y', '{id}'), {'request': '/requests/' + str(N) + '/3', 'decision': ['%252F', '/%2F', 'c', False, 'x%3Dy', '{id}', False, False, 3, 1]})
check('fixture 5', solve('/requests/' + str(N) + '/4', '/{id}', 'café', ['a'], 2, 'a b', '{{id}}'), {'request': '/requests/' + str(N) + '/4', 'decision': ['caf%C3%A9', '/café', None, True, 'a%20b', '{{id}}', False, False, 5, 1]})
check('fixture 6', solve('/requests/' + str(N) + '/5', '/{id}', '', [''], 0, '#frag', ''), {'request': '/requests/' + str(N) + '/5', 'decision': ['', '/', '', False, '%23frag', '', False, True, 0, 1]})
check('fixture 7', solve('/requests/' + str(N) + '/6', '/{other}/{id}', '/a//b', ['x'], 0, 'a/b', 'literal'), {'request': '/requests/' + str(N) + '/6', 'decision': ['%2Fa%2F%2Fb', '/{other}//a//b', 'x', False, 'a%2Fb', 'literal', True, False, 5, 1]})
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 |
|---|---|---|---|
| fixture 1 | {'decision': ['a%2Fb', '/item/a/b', 'one', False, 'a%26b', '{id}', False, False, 3, 1], 'request': '/requests/1/0'} | {'decision': ['a%2Fb', '/item/a/b', 'one', False, 'a%26b', '{id}', False, False, 3, 1], 'request': '/requests/1/0'} | Passed |
| fixture 2 | {'decision': ['x%20y', '/x y/x y', 'only', False, 'a%2Bb', 'plain', False, False, 3, 2], 'request': '/requests/1/1'} | {'decision': ['x%20y', '/x y/x y', 'only', False, 'a%2Bb', 'plain', False, False, 3, 2], 'request': '/requests/1/1'} | Passed |
| fixture 3 | {'decision': ['z', '/fixed', None, True, '', '{missing}', False, False, 1, 0], 'request': '/requests/1/2'} | {'decision': ['z', '/fixed', None, True, '', '{missing}', False, False, 1, 0], 'request': '/requests/1/2'} | Passed |
| fixture 4 | {'decision': ['%252F', '/%2F', 'c', False, 'x%3Dy', '{id}', False, False, 3, 1], 'request': '/requests/1/3'} | {'decision': ['%252F', '/%2F', 'c', False, 'x%3Dy', '{id}', False, False, 3, 1], 'request': '/requests/1/3'} | Passed |
| fixture 5 | {'decision': ['caf%C3%A9', '/café', None, False, 'a%20b', '{{id}}', False, False, 5, 1], 'request': '/requests/1/4'} | {'decision': ['caf%C3%A9', '/café', None, True, 'a%20b', '{{id}}', False, False, 5, 1], 'request': '/requests/1/4'} | Failed |
| fixture 6 | {'decision': ['', '/', '', False, '%23frag', '', False, True, 0, 1], 'request': '/requests/1/5'} | {'decision': ['', '/', '', False, '%23frag', '', False, True, 0, 1], 'request': '/requests/1/5'} | Passed |
| fixture 7 | {'decision': ['%2Fa%2F%2Fb', '/{other}//a//b', 'x', False, 'a%2Fb', 'literal', True, False, 5, 1], 'request': '/requests/1/6'} | {'decision': ['%2Fa%2F%2Fb', '/{other}//a//b', 'x', False, 'a%2Fb', 'literal', True, False, 5, 1], 'request': '/requests/1/6'} | Passed |
SHA-256 / 17a92ca3d82d1dd9360f19f6004bdd5de852c2aba57a1b048f52483441b22aba
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 7 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.
Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.
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Sign in to the archive ↗Verification & scope
Stipulated offline redirect policy, not a complete HTTP, browser, URL, cache, or security implementation. Numbered variants vary request correlation identity. 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 2026-09-29T14:41:36.199097+00:00.
Case digest / e4b32f3627afeb684c76f0e05e151f5364b69a36eb8a01f3e6f2eb5f80382c6b