Changelog

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All notable changes to erli18n will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning 2.0.0.

Versioning policy

Per SemVer 2.0.0 §4, this project is in the 0.x.y initial-development phase:

  • 0.x.y → 0.x.y+1 (patch): backward-compatible bug fixes only.
  • 0.x.y → 0.x+1.0 (minor): may introduce backward-incompatible changes, announced in advance via CHANGELOG. Additive changes (new functions, new arities, new opt-in flags, new telemetry events) are the norm.
  • Telemetry events are versioned per the schema policy documented in the erli18n_telemetry module -moduledoc; events marked @stable cannot change schema within 0.x series, events marked @unstable may.

Criteria for 1.0.0

The 1.0.0 release commits to API stability. Tag bumps to 1.0.0 only when all of the following hold:

  1. At least one external project uses erli18n in production for ≥ 6 months without reporting breaking issues.
  2. The Post-0.1.0 Roadmap items that affect public API surface (charset support, hot upgrade behavior, async load) are either implemented or formally rejected with rationale.
  3. Parity SUITE (erli18n_parity_SUITE) passes end-to-end against the real GNU gettext / ngettext CLI (gettext-tools ≥ 0.21) as oracle (currently 6 scenarios; target ≥ 20 covering the full PSD-001…009 semantics matrix).
  4. No unfixed @unstable telemetry events remain — all events either promoted to @stable or removed.
  5. CHANGELOG documents zero behavioral changes for at least 2 consecutive minor releases.

[Unreleased]

No unreleased changes.

[0.3.0] — 2026-06-19

Phase 2: canonicalization-aware BCP-47 fallback chain + Accept-Language negotiation (opt-in). This release is additive — a new module, four new facade functions, one new application-env key defaulting to off, and one new telemetry event under the existing opt-in flag. With the default configuration every public function behaves exactly as in 0.2.0; the exact-match lookup hot path is byte-for-byte unchanged and reads nothing extra. The minor bump follows the 0.x SemVer policy above.

Added

  • erli18n_negotiate — a pure, total, dependency-free engine for locale canonicalization, fallback-chain construction, and Accept-Language negotiation. Holds no state (no gen_server, ETS, or process dictionary) and is property-tested in isolation.
    • canonicalize/1 — folds a BCP-47 / POSIX tag to the erli18n catalog-key shape (<<"pt-BR">> → <<"pt_BR">>): hyphen/underscore equivalence, RFC 5646 §2.1.1 positional casing (language lowercase, script Titlecase, region UPPERCASE), POSIX charset/modifier suffix stripping (pt_BR.UTF-8, ca_ES@valencia), and a closed legacy-language alias table (in→id, iw→he, ji→yi, jw→jv, mo→ro). Total and idempotent. Out of scope (documented non-goals): macrolanguage/script inference such as zh_Hans ⇄ zh_CN (needs the CLDR Add Likely Subtags algorithm) and grandfathered/irregular tags.
    • fallback_chain/2 — the ordered RFC 4647 Lookup candidate list (pt-BR + default en → [<<"pt_BR">>, <<"pt">>, <<"en">>]), canonicalized, order-preserving-deduplicated, and bounded.
    • parse_accept_language/1 — parses an HTTP Accept-Language header (RFC 9110 §12.5.4) into [{Range, Q}] with Q as an integer in milli-units (0..1000); absent q = 1000, well-formed q=0 dropped, sorted by descending quality with a stable header-order tiebreak. Total and fail-soft; output shape matches cowlib's cow_http_hd:parse_accept_language/1.
    • negotiate/2,3 and best_match/3 — RFC 4647 Lookup of a preference list against an available-locale set, returning the first supported match (preserving the available entry's original casing), a default, or error.
  • Facade additions on erli18n — negotiate/2 (always returns a usable locale, defaulting to default_locale/0 on no match), parse_accept_language/1, canonicalize_locale/1, and set_locale_fallback/1. None changes an existing arity.
  • Opt-in lookup fallback chain — the four lookup families (gettext / ngettext / pgettext / npgettext, and so the interpolating f-family that delegates to them) consult the fallback chain only on an exact-match miss and only when enabled, so a pt_BR request resolves a loaded pt catalog instead of returning the raw msgid.
  • Config erli18n.locale_fallback (env, default off):
    • off — exact match only (0.2.0 behavior; the hit path reads nothing extra).
    • base_language — RFC 4647 Lookup chain (pt_BR → pt → default_locale).
    • {explicit, Map} — Map :: #{locale() => [locale()]} override layer; an unlisted locale falls through to base_language.
  • Telemetry [erli18n, locale, fallback] — emitted when a non-exact locale resolves a translation through the chain, with a chain_depth measurement and requested_locale / resolved_locale metadata. Opt-in under the existing emit_lookup_telemetry flag and kept entirely off the exact-hit path.
  • event_locale_fallback/0 on erli18n_telemetry.

Performance & safety

  • Zero-overhead exact hit. All fallback work runs strictly in the post-miss branch and only when enabled; an exact hit remains a single ets:lookup with no extra allocation or config read (verified by a dedicated CT case). On a miss with fallback on, cost is O(chain length) extra reads, short-circuiting on the first hit.
  • Total / fail-soft & anti-DoS. Parsing untrusted tags and headers never raises and never interns atoms (no binary_to_atom); bounded by per-tag (35 B), subtag (8), chain (8), header (4096 B), element (64), and range (32) caps. An invalid locale_fallback value degrades to off rather than breaking a lookup.

Caveats

  • Likely-subtags inference is not performed. zh-CN canonicalizes to zh_CN, not zh_Hans; a script-only catalog (zh_Hans) is not matched by a region-only request (zh_CN) or vice versa. Load catalogs under the keys your clients send, or supply an {explicit, Map} mapping.

[0.2.0] — 2026-06-16

Phase 1: named %{var} interpolation. This release is additive — every change is a new function, type, or module; the existing gettext / ngettext / pgettext / npgettext families (and their d / dc variants) are behaviorally unchanged. The minor bump follows the 0.x SemVer policy above.

Added

  • erli18n_interp — a pure, dependency-free substituter for named %{name} placeholders. format/2 (lenient) is total and fail-soft: for any input and any bindings it returns a binary and never raises. format/3 takes an opts() map whose single key, on_missing, selects the missing-binding policy (lenient | strict).
    • Named placeholders. %{name} decouples wording from argument order — a translator can move or repeat %{name} and the binding still resolves by name (atom keys). Values may be a binary, an iolist/string, an integer, a float, or an atom, and are coerced to UTF-8 text.
    • Escaping. A literal percent is %%; to emit a literal, un-substituted %{name}, write %%{name} (the %% collapses to %, leaving {name} untouched).
    • lenient vs strict. Lenient leaves an unbound %{name} in place literally; strict raises {erli18n_interp, {missing_binding, Name}}.
    • Anti-DoS caps. Output is bounded by ?MAX_OUTPUT_BYTES (65536): every append (literal chunk, coerced bound value, literal placeholder) is size-checked in O(1) and the result is truncated to fit before scanning stops. Placeholder expansion is bounded by ?MAX_EXPANSIONS (1024); past that, placeholders are emitted literally. Truncation/clamp paths use binary:copy/1 so the returned binary does not pin a large parent binary.
  • bindings/0 type — #{atom() => term()}, exported from erli18n_interp (alongside on_missing/0 and opts/0).
  • Interpolating f-suffix façade family — 24 new functions on erli18n: gettextf, ngettextf, pgettextf, npgettextf and their d / dc domain-explicit variants, each with a process-locale and an explicit-locale arity. Every f function resolves the translation exactly like its non-f sibling, then splices %{var} values from a trailing Bindings :: map(). The façade f family is lenient (unbound placeholders stay literal; never raises); opt into strict by calling erli18n_interp:format/3 directly.
  • Plural count auto-bind. The ngettextf / npgettextf families auto-bind count => N, so %{count} is always available without passing it; a caller-supplied count wins.

Caveats

  • Bidi / RTL. Interpolation does not auto-insert Unicode bidi isolation marks (U+2066–U+2069) around spliced values. Placing an RTL value into an LTR sentence (or the reverse) can reorder neighbouring punctuation under the Unicode Bidirectional Algorithm. Isolate mixed-direction values yourself until a future version offers opt-in isolation.

[0.1.0] — 2026-06-14

Initial development release. The public API is functional but subject to backward-incompatible changes on minor bumps per the 0.x SemVer policy.

Requires OTP 27 or newer. The public modules carry native -doc / -moduledoc documentation attributes (EEP-59), which only compile on OTP 27+; OTP 25.3 and 26 reject them at compile time with attribute doc after function definitions.

Added

  • Core OTP application: erli18n_app, erli18n_sup (intensity {5, 10} hardcoded per AMB-002).
  • erli18n_server — genserver + ETS catalog store with anti-bottleneck pattern (hot path `lookup*is lock-free direct ETS from caller process; writes serialized throughprotected` table owner).
  • erli18n_po — hand-written recursive-descent parser for GNU gettext .po format. Honors PSDs 001-009:
    • PSD-001: fuzzy entries dropped by default; opt-in via #{include_fuzzy => true}.
    • PSD-002: charset support restricted to UTF-8, Latin-1, US-ASCII (native to unicode:characters_to_binary/3).
    • PSD-003: empty msgstr preserved; fallback-to-msgid handled at lookup.
    • PSD-004: header Plural-Forms is runtime source of truth; CLDR consulted at load only for divergence warning.
    • PSD-005: BOM UTF-8 stripped silently.
    • PSD-006: msgctxt stored as a separate ETS key field, matching how GNU gettext keys contextual entries (msgctxt + EOT + msgid).
    • PSD-007: obsolete #~ entries skipped.
    • PSD-008: degenerate plural (nplurals=1) accepted.
    • PSD-009: nplurals mismatch rejected with structured error.
  • erli18n_plural — recursive-descent C-expression evaluator for Plural-Forms header. CLDR data inlined for 49 locales. Bignum-clean.
  • erli18n_server:ensure_loaded/3,4 and reload/3,4 — atomic catalog load (parse → compile plural → validate vs CLDR → insert), with idempotency fast-path (RISK-012 mitigation).
  • erli18n (façade) — full GNU gettext C-macro API surface: gettext family (singular), ngettext family (plural), pgettext family (contextual), npgettext family (contextual + plural), with d/dc aliases. Per-process locale via process dictionary; application-wide defaults via application:get_env/2.
  • erli18n_telemetry — 7 :telemetry events as first-class observability concern (catalog load/reload/unload spans; lookup miss/fuzzy_skip opt-in; plural divergence warning; memory warning rate-limited). telemetry declared as optional dep via optional_applications (OTP 24+).
  • Test suite: 289 Common Test cases, green on OTP 27 and 28 — façade API, gen_server / catalog, .po parser, plural evaluator, loader, and telemetry suites, plus PropEr properties (200 runs each) and fuzz scenarios (100–500 runs each). 6 of these are parity scenarios run against the real GNU gettext / ngettext CLI oracle; that suite skips cleanly when gettext-tools or the pt_BR.UTF-8 / ru_RU.UTF-8 locales are absent.
  • Coverage: 100% of behaviorally reachable lines. Dead defensive code removed (no silent fallbacks for invariant violations — crashes are explicit via function_clause / case_clause / badmatch).
  • Apache 2.0 license.
  • GitHub Actions CI (.github/workflows/ci.yml) — three jobs on pinned ubuntu-24.04 runners: lint (fast quality gate on OTP 28), test (Common Test + coverage across OTP 27 and 28, with gettext installed and the pt_BR.UTF-8 / ru_RU.UTF-8 locales generated so erli18n_parity_SUITE exercises the oracle path), dialyzer (isolated job with PLT cache). CI runs automatically only on main; every other branch runs on demand via workflow_dispatch. Concurrency cancellation per ref, least-privilege contents: read token, rebar3 build cache keyed per OTP.
  • Local CI emulation via act and a custom runner image (Dockerfile.act-runner): extends ghcr.io/catthehacker/ubuntu:full-24.04 with ELP 2026-02-27 (SHA256-verified per SLSA v0.2). Reuses the workflow YAML unchanged — GitHub-hosted runners gracefully [SKIP] the ELP steps in real CI. Bootstrap is declarative in compose.yml (act-toolcache volume init + image build). actionlint 1.7.12 pinned via mise.toml for static workflow analysis.
  • Repo hygiene: README.md (with usage / install / compatibility / dev sections), CONTRIBUTING.md, SECURITY.md, CODE_OF_CONDUCT.md (Contributor Covenant 3.0), .editorconfig.

Architecture decisions

The design rationale is captured inline in the source: PO-semantics decisions (PSD-001…PSD-009), risk mitigations (RISK-*), and ambiguity resolutions (AMB-*) are referenced from the relevant module -moduledoc / -doc attributes and code comments. The internal planning corpus that originally tracked them is not part of the published package.