idna 3.11: uts46_remap

# idna: UTS46 Domain Remapping (idna.uts46_remap)

## Prior Network Solutions

The network query for `verify idna.uts46_remap in pkg:pypi/idna@3.11` returned NO_SAFE_MATCH.

## Release Pinned

- `idna`: 3.11

## Observed Behaviour

In `idna` 3.11:
1. `uts46_remap` normalizes domain strings with Unicode case folding and NFC normalization (e.g. `EXAMPLE.COM` -> `example.com`, `KÖLN.DE` -> `köln.de`).
2. Label separators such as fullwidth dots (`\u3002`, `\uff0e`) are remapped to standard ASCII dots (`.`).
3. Ignored characters (UTS#46 status 'I', e.g. Zero-Width Space `\u200b`) are stripped from output.
4. Deviation characters (UTS#46 status 'D', e.g. German Eszett `ß` `\u00df` and Greek final sigma `ς` `\u03c2`) are preserved when `transitional=False` and mapped to replacement sequences (`ss`, `σ`) when `transitional=True`.
5. Disallowed characters (UTS#46 status 'X', e.g. `\x80`, `\u200e`) raise `idna.InvalidCodepoint`.

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 idna.uts46_remap in pkg:pypi/idna@3.11
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:pypi/idna@3.11
Demonstrate these symbols/APIs:
  - idna.uts46_remap

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:sha256:4407aa747fa3bf4295563e57196d521525b774cabf3e7f247b4b237e04826197","contract":["uts46_remap normalizes domain names with case folding and NFC normalization","uts46_remap maps fullwidth and ideographic label separators to ASCII dots","uts46_remap removes characters with status I (ignored) such as zero-width spaces","uts46_remap preserves deviation characters when transitional=False and replaces them when transitional=True","uts46_remap raises InvalidCodepoint for disallowed UTS46 codepoints"],"goal":"verify idna.uts46_remap in pkg:pypi/idna@3.11","kind":"HOW","packages":["pkg:pypi/idna@3.11"],"schemaVersion":1,"symbols":["idna.uts46_remap"]},"contractCommand":["python","test/contract.py"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"pypi","executionContext":"python","language":"python","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"pip","runtime":"python","runtimeVersion":"3.12","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/idna@3.11"],"schemaVersion":1,"subject":"pkg:pypi/idna@3.11","symbols":["idna.uts46_remap"],"verifierAdapter":"python@1"}

idna==3.11

{
  "schemaVersion": 1,
  "goal": "verify idna.uts46_remap in pkg:pypi/idna@3.11",
  "kind": "HOW",
  "packages": [
    "pkg:pypi/idna@3.11"
  ],
  "symbols": [
    "idna.uts46_remap"
  ]
}

import idna


def main() -> None:
    # 1. Unicode case folding and normalization (NFC)
    assert idna.uts46_remap("EXAMPLE.COM") == "example.com"
    assert idna.uts46_remap("KÖLN.DE") == "köln.de"

    # 2. Remapping label separators to ASCII dot
    assert idna.uts46_remap("example\u3002com") == "example.com"
    assert idna.uts46_remap("example\uff0ecom") == "example.com"

    # 3. Ignored characters (status 'I') such as Zero-Width Space are deleted
    assert idna.uts46_remap("sub\u200bdomain.example.com") == "subdomain.example.com"

    # 4. Deviation characters (status 'D') with transitional flag
    # German Eszett 'ß' (U+00DF): preserved when transitional=False, mapped to 'ss' when transitional=True
    assert idna.uts46_remap("faß.de", transitional=False) == "faß.de"
    assert idna.uts46_remap("faß.de", transitional=True) == "fass.de"

    # Greek final sigma 'ς' (U+03C2): preserved when transitional=False, mapped to small sigma 'σ' when transitional=True
    assert idna.uts46_remap("βόλος.com", transitional=False) == "βόλος.com"
    assert idna.uts46_remap("βόλος.com", transitional=True) == "βόλοσ.com"

    # 5. Disallowed codepoints raise idna.InvalidCodepoint
    for invalid_char in ["\x80", "\u200e", "\u202e"]:
        try:
            idna.uts46_remap(f"bad{invalid_char}.example.com")
            raise AssertionError(f"Expected InvalidCodepoint for codepoint {hex(ord(invalid_char))}")
        except idna.InvalidCodepoint as exc:
            assert f"Codepoint U+{ord(invalid_char):04X}" in str(exc)


if __name__ == "__main__":
    main()