idna 3.18

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:pypi/idna@3.18
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:pypi/idna@3.18

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:3918e0b6b4c2e273ac17009ef626df6acb629776761c29441963951adaaf4f1f","contract":["idna.encode converts internationalized domain names into Punycode ASCII-compatible encoding bytes and preserves trailing dots","idna.encode with uts46=True normalizes uppercase characters before encoding","idna.encode raises IDNAError when domain is empty or contains empty labels","idna.decode decodes Punycode byte sequences and string representations to Unicode domain strings","idna.decode raises IDNAError on malformed Punycode labels","idna.alabel and idna.ulabel convert individual domain labels between Unicode and ACE bytes","idna.uts46_remap remaps and normalizes domain names following Unicode UTS 46","idna.check_bidi validates bidirectional domain name labels"],"goal":"verify pkg:pypi/idna@3.18","kind":"HOW","packages":["pkg:pypi/idna@3.18"],"schemaVersion":1},"contractCommand":["python","test/contract.py"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"pypi","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"pip","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/idna@3.18"],"schemaVersion":1,"subject":"pkg:pypi/idna@3.18","verifierAdapter":"python@1"}

idna==3.18

{
  "schemaVersion": 1,
  "goal": "verify pkg:pypi/idna@3.18",
  "kind": "HOW",
  "packages": [
    "pkg:pypi/idna@3.18"
  ]
}

import idna
import idna.core


def test_encode() -> None:
    # 1. idna.encode converts internationalized domain names into Punycode ASCII-compatible encoding bytes and preserves trailing dots
    assert idna.encode("домен.is") == b"xn--d1acufc.is"
    assert idna.encode("example.com") == b"example.com"
    assert idna.encode("köln.de.") == b"xn--kln-sna.de."

    # 2. idna.encode with uts46=True normalizes uppercase characters before encoding
    assert idna.encode("KÖLN.de", uts46=True) == b"xn--kln-sna.de"

    # 3. idna.encode raises IDNAError when domain is empty or contains empty labels
    try:
        idna.encode("")
        raise AssertionError("Expected IDNAError for empty domain")
    except idna.IDNAError as exc:
        assert isinstance(exc, idna.IDNAError)

    try:
        idna.encode("a..b")
        raise AssertionError("Expected IDNAError for consecutive dots")
    except idna.IDNAError as exc:
        assert isinstance(exc, idna.IDNAError)


def test_decode() -> None:
    # 4. idna.decode decodes Punycode byte sequences and string representations to Unicode domain strings
    assert idna.decode(b"xn--d1acufc.is") == "домен.is"
    assert idna.decode("xn--kln-sna.de") == "köln.de"
    assert idna.decode(b"example.com.") == "example.com."

    # 5. idna.decode raises IDNAError on malformed Punycode labels
    try:
        idna.decode(b"xn--invalid_label_12345!")
        raise AssertionError("Expected IDNAError for malformed label")
    except idna.IDNAError as exc:
        assert isinstance(exc, idna.IDNAError)


def test_label_conversion() -> None:
    # 6. idna.alabel and idna.ulabel convert individual domain labels between Unicode and ACE bytes
    assert idna.alabel("köln") == b"xn--kln-sna"
    assert idna.ulabel(b"xn--kln-sna") == "köln"
    assert idna.ulabel("xn--kln-sna") == "köln"


def test_uts46_remap() -> None:
    # 7. idna.uts46_remap remaps and normalizes domain names following Unicode UTS 46
    assert idna.uts46_remap("EXAMPLE.COM") == "example.com"
    assert idna.uts46_remap("KÖLN.DE", std3_rules=True) == "köln.de"
    assert idna.uts46_remap("faß.de", transitional=False) == "faß.de"
    assert idna.uts46_remap("faß.de", transitional=True) == "fass.de"


def test_check_bidi() -> None:
    # 8. idna.check_bidi validates bidirectional domain name labels
    assert idna.check_bidi("abc") is True


def main() -> None:
    test_encode()
    test_decode()
    test_label_conversion()
    test_uts46_remap()
    test_check_bidi()
    print("All contract assertions passed.")


if __name__ == "__main__":
    main()