0.4.0 Release Notes

2026-06-27 · first release on hex.pm

The capstone of the migration: lfmt is now an installable, dependency-free
library with a stable public API.

{deps, [{lfmt, "~> 0.4"}]}.

Highlights

• First public release on hex.pm. Zero runtime dependencies; OTP 27+.
• Multi-engine public API. A single stable surface sits in front of
  pluggable formatting engines:
  • lfmt:format/1 — format with the default engine.
  • lfmt:new/1 + lfmt:format/2 — build a reusable formatter for a chosen
    engine, e.g. lfmt:new(#{engine => fezzik}).
  • An lfmt_engine behaviour and a shared #lfmt_opts{} record define the
    contract the future pe/pc engines implement.
  • The fezzik engine ships; pe/pc are reserved — selecting one that
    isn't available yet is reported explicitly, never silently ignored.
• Renderer decomposed (pure, behaviour-identical refactor). The monolithic
  lfmt_fezzik.erl (~1,870 lines) was split into a thin orchestrator plus a
  render core (lfmt_fezzik_render), leaf helpers (lfmt_fezzik_util), and a
  shared lfmt_fezzik.hrl, with strictly one-way layering
  (lexer → cst → util → render → fezzik). Verified byte-identical against the
  pre-split output over the full corpus.
• Adopted by rebar3_lfe. As of rebar3_lfe 0.5.5, the rebar3 lfe format
  provider delegates to lfmt; its bundled formatter engine has been removed.
• Honest test harness. The corpus sweep now flattens output via the
  Unicode-safe path, so all 32 corpus files are exercised (previously 2 multibyte
  files were silently skipped).
• Local CI parity. A Makefile mirrors every CI job — run make ci to
  reproduce the full gate locally before pushing.

Usage

{ok, IoData} = lfmt:format(<<"(defun id (x) x)">>),
Bin = unicode:characters_to_binary(IoData).

Formatted output can contain Unicode codepoints (> 127), so convert it with
unicode:characters_to_binary/1 — not iolist_to_binary/1.

0.3.0 Release Notes

2026-06-26 · migration milestone (not published to hex)

• Renamed under the lfmt namespace. Engine modules r3lfe_format* →
  lfmt_fezzik*; the OTP application fmt → lfmt. Hex package metadata
  (description, Apache-2.0 license, project links) staged for the upcoming
  release.
• Unicode-honest test harness. Removed the 7-bit-ASCII carve-out that had
  excluded multibyte source files from the inline oracles. The oracles now
  flatten formatter output with unicode:characters_to_binary, so the multibyte
  corpus files (core-macros.lfe, clj-tests.lfe) are fully exercised. This
  closes a latent harness defect carried since 0.1.0.

0.2.0 Release Notes

2026-06-25 · migration milestone (not published to hex)

• Refined the brute-force formatting rules (the "rules v2" design record),
  carried in with history.
• Removed the docs/design/022-lfe-format/ staging directory now that the design
  record lives under the project's planning tree.

0.1.0 Release Notes

2026-06-15 · migration milestone (not published to hex)

• Established the standalone repo. The "Fezzik" brute-force LFE formatter was
  extracted from rebar3_lfe into lfe/fmt with full git history preserved.
• A working LFE pretty-printer. Reads LFE source and emits a consistent,
  canonical layout — preserving comments and guaranteeing idempotence
  (format(format(X)) == format(X)).
• Real test substrate. A 32-file real-world corpus plus a four-oracle harness
  checking idempotence, token preservation, AST equivalence, and comment
  preservation.