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FA-76641 / Email MIME structure / Open access

Collect the plain-text body to display: alternative empty skip · case 01

An HTML-only last alternative produces an empty display although a text alternative exists.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The alternative empty skip decision evaluates `if True:` where the contract requires `if got:`.

VERIFIED REPAIR

Use `if got:` for the alternative empty skip decision and keep every other rule of the model unchanged.

Unsuccessful approach: An empty list is not None, so the empty HTML result is still accepted. The attempted `if got is not None:` still disagrees with a fixture.

Case contract

Returns the text/plain strings to display in order. Types compare case-insensitively. multipart/alternative yields the result of its last child that yields any text; other multiparts concatenate their children. Entities with an attachment disposition yield nothing. A message/rfc822 without attachment disposition yields its body; text/plain yields its text; everything else yields nothing.

Why this case matters

Text extraction powers previews, replies and search; wrong choices quote attachments or skip the real body.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(tree):
    def walk(n):
        t = n['type'].lower()
        disp = (n.get('disp') or 'inline').lower()
        if t == 'multipart/alternative':
            for child in reversed(n['parts']):
                got = walk(child)
                if True:
                    return got
            return []
        if t.startswith('multipart/'):
            out = []
            for child in n['parts']:
                out.extend(walk(child))
            return out
        if disp == 'attachment':
            return []
        if t == 'message/rfc822':
            return walk(n['body'])
        if t == 'text/plain':
            return [n['text']]
        return []
    return walk(tree)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A1'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B1'}, {'type': 'image/png'}]}]},), ['B1']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 1'}, {'type': 'text/html'}]},), ['plain 1']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 1'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw1'}, {'type': 'text/html'}]}}]},), ['x', 'fw1']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't1'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t1', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 2: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A2'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B2'}, {'type': 'image/png'}]}]},), ['B2']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 2'}, {'type': 'text/html'}]},), ['plain 2']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 2'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw2'}, {'type': 'text/html'}]}}]},), ['x', 'fw2']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't2'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t2', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 3: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A3'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B3'}, {'type': 'image/png'}]}]},), ['B3']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 3'}, {'type': 'text/html'}]},), ['plain 3']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 3'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw3'}, {'type': 'text/html'}]}}]},), ['x', 'fw3']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't3'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t3', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 4: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A4'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B4'}, {'type': 'image/png'}]}]},), ['B4']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 4'}, {'type': 'text/html'}]},), ['plain 4']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 4'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw4'}, {'type': 'text/html'}]}}]},), ['x', 'fw4']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't4'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t4', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 5: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A5'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B5'}, {'type': 'image/png'}]}]},), ['B5']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 5'}, {'type': 'text/html'}]},), ['plain 5']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 5'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw5'}, {'type': 'text/html'}]}}]},), ['x', 'fw5']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't5'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t5', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])]}
for _label, _args, _expected in _CASES[N]:
    check(_label, solve(*_args), _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 fixtureActualExpectedOutcome
richer alternative holds text['B1']['B1']Passed
html last alternative[]['plain 1']Failed
attached message and log['hi']['hi']Passed
inline forwarded alternative['x']['x', 'fw1']Failed
mixed-case types['t1', 'u']['t1', 'u']Passed
no text at all[][]Passed

SHA-256 / 5bb0c4fac26004cb6133b39d7e437021d5cb4e60bb8f1c0e0b0d97ee970d255d

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(tree):
    def walk(n):
        t = n['type'].lower()
        disp = (n.get('disp') or 'inline').lower()
        if t == 'multipart/alternative':
            for child in reversed(n['parts']):
                got = walk(child)
                if got is not None:
                    return got
            return []
        if t.startswith('multipart/'):
            out = []
            for child in n['parts']:
                out.extend(walk(child))
            return out
        if disp == 'attachment':
            return []
        if t == 'message/rfc822':
            return walk(n['body'])
        if t == 'text/plain':
            return [n['text']]
        return []
    return walk(tree)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A1'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B1'}, {'type': 'image/png'}]}]},), ['B1']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 1'}, {'type': 'text/html'}]},), ['plain 1']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 1'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw1'}, {'type': 'text/html'}]}}]},), ['x', 'fw1']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't1'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t1', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 2: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A2'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B2'}, {'type': 'image/png'}]}]},), ['B2']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 2'}, {'type': 'text/html'}]},), ['plain 2']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 2'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw2'}, {'type': 'text/html'}]}}]},), ['x', 'fw2']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't2'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t2', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 3: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A3'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B3'}, {'type': 'image/png'}]}]},), ['B3']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 3'}, {'type': 'text/html'}]},), ['plain 3']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 3'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw3'}, {'type': 'text/html'}]}}]},), ['x', 'fw3']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't3'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t3', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 4: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A4'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B4'}, {'type': 'image/png'}]}]},), ['B4']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 4'}, {'type': 'text/html'}]},), ['plain 4']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 4'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw4'}, {'type': 'text/html'}]}}]},), ['x', 'fw4']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't4'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t4', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 5: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A5'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B5'}, {'type': 'image/png'}]}]},), ['B5']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 5'}, {'type': 'text/html'}]},), ['plain 5']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 5'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw5'}, {'type': 'text/html'}]}}]},), ['x', 'fw5']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't5'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t5', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])]}
for _label, _args, _expected in _CASES[N]:
    check(_label, solve(*_args), _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 fixtureActualExpectedOutcome
richer alternative holds text['B1']['B1']Passed
html last alternative[]['plain 1']Failed
attached message and log['hi']['hi']Passed
inline forwarded alternative['x']['x', 'fw1']Failed
mixed-case types['t1', 'u']['t1', 'u']Passed
no text at all[][]Passed

SHA-256 / c92a2d045aafe5ccaf76ea8daec4bf965cafc80e9d6d083ec99750b9d7c00dff

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(tree):
    def walk(n):
        t = n['type'].lower()
        disp = (n.get('disp') or 'inline').lower()
        if t == 'multipart/alternative':
            for child in reversed(n['parts']):
                got = walk(child)
                if got:
                    return got
            return []
        if t.startswith('multipart/'):
            out = []
            for child in n['parts']:
                out.extend(walk(child))
            return out
        if disp == 'attachment':
            return []
        if t == 'message/rfc822':
            return walk(n['body'])
        if t == 'text/plain':
            return [n['text']]
        return []
    return walk(tree)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A1'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B1'}, {'type': 'image/png'}]}]},), ['B1']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 1'}, {'type': 'text/html'}]},), ['plain 1']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 1'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw1'}, {'type': 'text/html'}]}}]},), ['x', 'fw1']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't1'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t1', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 2: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A2'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B2'}, {'type': 'image/png'}]}]},), ['B2']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 2'}, {'type': 'text/html'}]},), ['plain 2']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 2'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw2'}, {'type': 'text/html'}]}}]},), ['x', 'fw2']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't2'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t2', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 3: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A3'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B3'}, {'type': 'image/png'}]}]},), ['B3']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 3'}, {'type': 'text/html'}]},), ['plain 3']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 3'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw3'}, {'type': 'text/html'}]}}]},), ['x', 'fw3']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't3'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t3', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 4: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A4'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B4'}, {'type': 'image/png'}]}]},), ['B4']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 4'}, {'type': 'text/html'}]},), ['plain 4']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 4'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw4'}, {'type': 'text/html'}]}}]},), ['x', 'fw4']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't4'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t4', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])], 5: [('richer alternative holds text', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'A5'}, {'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'B5'}, {'type': 'image/png'}]}]},), ['B5']), ('html last alternative', ({'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'plain 5'}, {'type': 'text/html'}]},), ['plain 5']), ('attached message and log', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'hi'}, {'type': 'message/rfc822', 'disp': 'attachment', 'body': {'type': 'text/plain', 'text': 'inner'}}, {'type': 'text/plain', 'disp': 'attachment', 'text': 'log 5'}]},), ['hi']), ('inline forwarded alternative', ({'type': 'multipart/mixed', 'parts': [{'type': 'text/plain', 'text': 'x'}, {'type': 'message/rfc822', 'body': {'type': 'multipart/alternative', 'parts': [{'type': 'text/plain', 'text': 'fw5'}, {'type': 'text/html'}]}}]},), ['x', 'fw5']), ('mixed-case types', ({'type': 'MULTIPART/Mixed', 'parts': [{'type': 'Text/Plain', 'text': 't5'}, {'type': 'TEXT/PLAIN', 'text': 'u'}]},), ['t5', 'u']), ('no text at all', ({'type': 'multipart/mixed', 'parts': [{'type': 'image/png'}, {'type': 'application/pdf'}]},), [])]}
for _label, _args, _expected in _CASES[N]:
    check(_label, solve(*_args), _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 fixtureActualExpectedOutcome
richer alternative holds text['B1']['B1']Passed
html last alternative['plain 1']['plain 1']Passed
attached message and log['hi']['hi']Passed
inline forwarded alternative['x', 'fw1']['x', 'fw1']Passed
mixed-case types['t1', 'u']['t1', 'u']Passed
no text at all[][]Passed

SHA-256 / f1be4396ec22927d1b8a710afb41affde67f9ec6d7239ad0d04e2efbb6c09514

Verification & scope

Stipulated offline model over pre-parsed MIME dictionaries; not a conforming MIME parser, generator or mail client. 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 2026-09-29T14:49:18.055892+00:00.

Case digest / 80860f72560134d4e31e7b63e0b472bb8a9ac34ee8bd100790c1b56dbd53dd24