---
id: config-validation-and-trivia
name: Config robustness + trivia batch — ALPN dedup, empty-domains validation, packaging excludes, https doc line (C-2, C-3, N-6, N-7)
status: completed
depends_on: []
scope: narrow
risk: low
impact: component
level: implementation
tags: [robustness, packaging, docs, review-001, c2, c3, n6, n7]
---

## Description

Four small findings in one pass (all verified in the decomposition
session):

1. **C-2** — `acme-tls/1` is appended unconditionally
   (src/server.rs:91); a caller who already includes it in `alpns`
   gets it twice (probed: `alpn_protocols == [acme-tls/1, acme-tls/1]`).
   Harmless to rustls-acme's challenge dispatch today, but the
   duplication leaks into the wire config and the ACME/non-ACME
   asymmetry is undocumented. Fix: a one-line
   `if !alpn.contains(&b"acme-tls/1".to_vec())` guard — **or** pin the
   current shape in a doc note + test. The guard is the better
   default (idempotent construction), but either way a test pins the
   chosen shape.
2. **C-3** — `TlsIdentity::Acme` with an **empty** `domains` list
   constructs successfully (probed) and spawns the order loop that
   then fails per-order at runtime as logged-only events. A one-line
   validation (`if domains.is_empty() { return
   Err(TlsError::AcmeConfig("empty domain list".into())) }`) at
   construction is additive and cheap. Note: empty `contact` stays
   legal (RFC 8555 §7.3 allows zero-contact accounts) — do NOT
   validate that. **Mechanics note (2026-09-12 re-check): the new
   test must be `#[cfg(feature = "acme")]`-gated like the existing
   ACME tests — under default features the Acme arm already errors
   with `AcmeConfig` for the *missing-feature* reason (pinned by
   `new_acme_identity_without_feature_returns_config_error`,
   server.rs), so a non-gated empty-domains test would pass
   vacuously and prove nothing.**
3. **N-6** — `tasks/*.md` and `docs/architecture/**` ship in the
   published package (`cargo package --list` re-verified). One-line
   `exclude` addition: `"tasks/`, `"docs/architecture/` per the
   alktunnels house pattern (internal SDD notes + architecture docs
   don't belong in the public package).
4. **N-7** — `AcmeDirectory::Custom(String)` accepts any string and
   the URL goes to rustls-acme verbatim, so an `http://` custom
   directory silently runs ACME over plaintext (token-bearing). One
   doc line on the variant ("must be an `https://` ACME directory
   URL") closes it. Do not add runtime URL validation — the doc line
   is the fix (a caller pointing at a non-https *test* directory
   should not be blocked).

## Work

1. C-2: the dedup guard (preferred) + a test pinning
   idempotence (caller-supplied `acme-tls/1` → single entry).
2. C-3: the empty-domains validation + a test
   (`TlsServerConfig::new(&Acme{domains: vec![]}, ..)` →
   `TlsError::AcmeConfig`), feature-gated like the existing ACME
   tests.
3. N-6: `exclude = [... , "tasks/", "docs/architecture/"]`;
   re-run `cargo package --list --allow-dirty` + `cargo publish
   --dry-run --allow-dirty`.
4. N-7: the doc line on `AcmeDirectory::Custom`.

## Verification

- [ ] Dedup: caller-supplied `acme-tls/1` yields exactly one entry
      (test pinned)
- [ ] Empty-domains ACME construction errors with
      `TlsError::AcmeConfig` (test pinned)
- [ ] `cargo package --list --allow-dirty` contains neither `tasks/`
      nor `docs/architecture/`; `cargo publish --dry-run
      --allow-dirty` passes
- [ ] The `Custom` variant's doc states the https requirement
- [ ] `cargo test`, `--all-features`, clippy, fmt, doc green

## Acceptance Criteria

- [ ] All four findings resolved (or explicitly doc-pinned with a
      test, per finding)
- [ ] No behavior change beyond the three intended ones

## References

- docs/reviews/001-implementation-review.md §C-2, §C-3, §N-6, §N-7
- src/server.rs:91 (the ALPN append), src/server.rs:64-145
  (`new_acme` — where the domains validation goes),
  src/identity.rs:65 (`AcmeDirectory::Custom`), Cargo.toml:11
  (exclude list)
- (line refs re-checked 2026-09-12 against the post-ADR-007/008 tree;
  the file has shifted since the decomposition — re-grep before
  editing rather than trusting these absolutely)

## Notes

- C-2: implemented the dedup guard (preferred option) in `new_acme` —
  `if !alpn.contains(&b"acme-tls/1".to_vec())` before the push. Also
  documented the ACME/non-ACME ALPN asymmetry on
  `TlsServerConfig::new` (ACME always serves `acme-tls/1`, appended
  idempotently; non-ACME uses the caller's list verbatim). Pinned by
  `new_acme_caller_supplied_acme_tls_alpn_is_not_duplicated`
  (`src/server.rs`, `#[cfg(feature = "acme")]`).
- C-3: added the empty-domains validation at the top of `new_acme`
  (before any `AcmeConfig` construction or task spawn) returning
  `TlsError::AcmeConfig("TlsIdentity::Acme requires a non-empty domain
  list")`. `contact` left unvalidated per the finding (RFC 8555 §7.3
  zero-contact accounts are legal). Test
  `new_acme_empty_domains_returns_config_error` is
  `#[cfg(feature = "acme")]`-gated per the task's mechanics note.
- N-6: `exclude` now also lists `"tasks/"` and `"docs/architecture/"`.
  Verified `cargo package --list --allow-dirty` contains neither path
  and `cargo publish --dry-run --allow-dirty` passes.
- N-7: doc line added on `AcmeDirectory::Custom` (`src/identity.rs`):
  the URL goes to rustls-acme verbatim and must be `https://` (an
  `http://` URL would run ACME token-bearing over plaintext); explicitly
  notes no runtime validation is applied so non-https test directories
  stay usable. No runtime check added, per the finding.

## Summary

All four findings resolved. Changes:

1. `src/server.rs` — `new_acme` dedups the `acme-tls/1` ALPN append
   (idempotent construction) and rejects an empty `domains` list with
   `TlsError::AcmeConfig` before spawning the order loop; the
   ACME/non-ACME ALPN asymmetry is documented on `TlsServerConfig::new`.
2. `src/identity.rs` — `AcmeDirectory::Custom` documents the
   https-only caller contract (no runtime validation, per finding).
3. `Cargo.toml` — `exclude` gains `"tasks/"` and `"docs/architecture/"`.

New tests (both `#[cfg(feature = "acme")]`): caller-supplied
`acme-tls/1` yields exactly one entry; empty `domains` constructs to
`TlsError::AcmeConfig`.

Verification: `cargo test` (default) and `cargo test --all-features`
(77 lib tests, both new tests pass), `cargo clippy --all-targets -- -D
warnings`, `cargo fmt --check`, `cargo doc --no-deps`,
`cargo package --list --allow-dirty` (no `tasks/` / `docs/architecture/`
entries), `cargo publish --dry-run --allow-dirty` — all green.