# Changelog

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

The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).

## [0.12.0] - 2026-05-22

0.12.0 lands two internal-shape changes that compose on top of the
0.11.0 conditional-compilation work: contract closures move out of
override clauses into named private functions on the user's module
(reducing injected code per contract'd function), and `:telemetry`
events fire on assertion failures.

### Added

- **`[:bond, :assertion, :failure]` telemetry event.** Fires once per
  contract violation — `@pre`, `@post`, or `check` — immediately before
  the corresponding `Bond.PreconditionError` / `Bond.PostconditionError`
  / `Bond.CheckError` is raised. Single event family for all three
  kinds; consumers filter on the `:kind` metadata. Measurements carry
  `:system_time` and `:monotonic_time`; metadata carries `:kind`,
  `:module`, `:function`, `:label`, `:expression`, `:assertion_id`,
  `:file`, `:line`, and `:binding`. See the new "Telemetry" section in
  the `Bond` moduledoc / README. `{:telemetry, "~> 1.0"}` is now a
  regular dependency.

- **`Bond.Runtime.Eval.should_evaluate?/2`** — internal helper that
  performs the `Application.get_env/3` runtime guard. Used by the
  emission shape (see "Internal" below) to avoid allocating the
  assertion-evaluation closure when the runtime guard says skip.

### Changed

- **Per-function assertion closures are lifted into named `defp`s** on
  the using module: `__bond_preconditions__<fun>__<arity>` and
  `__bond_postconditions__<fun>__<arity>`. The override clause itself
  is now a small wrapper that calls these via
  `Bond.Runtime.Eval.evaluate_preconditions/1` /
  `evaluate_postconditions/1`. The big inline assertion-evaluation AST
  that used to be re-emitted into every override is gone; the BEAM
  carries one tiny override + one defp per non-purged kind, rather
  than the whole eval body inlined per function.

- **Runtime guard moved into `Bond.Runtime.Eval`.** The override calls
  `should_evaluate?(:preconditions, <compile_time_mode>)` and only
  builds the assertion-evaluation closure when that returns `true`.
  The `Application.get_env/3` lookup logic lives entirely in
  `Bond.Runtime` rather than being inlined at every contract'd
  function.

- **`Bond.check/1,2` routes through the same throw/catch path as
  `@pre`/`@post`.** All three kinds now produce
  `{:assertion_failure, info}` throws caught by `Bond.Runtime.Eval`,
  which fires the telemetry event and raises. This unifies the
  plumbing across the three kinds; previously `check` raised inline.

- **Stacktrace pruning** now also filters frames whose function name
  starts with `__bond_` (the lifted defps), so failures continue to
  point at the user's call site rather than into Bond-generated
  plumbing.

- **Benchmark** on the project fixture
  (`bench/runtime_check_overhead.exs`, trivial `@pre is_number(x)` in a
  tight loop):

  | mode    | 0.11.0   | 0.12.0   |
  |---------|----------|----------|
  | `:purge`  | ~48 ns   | ~34 ns   |
  | `true`    | ~155 ns  | ~143 ns  |
  | `false`   | ~89 ns   | ~91 ns   |

  The `true` path improves because the override no longer re-emits the
  full assertion-eval AST inline. The `false` (runtime-skip) path is
  flat within noise — `should_evaluate?/2` short-circuits before the
  closure is allocated.

### Fixed

- `Bond.CheckError`'s `message/1` no longer crashes when the error's
  `:function` metadata is missing (regression introduced and fixed
  internally during the `check` plumbing unification).

### Requirements

- Unchanged. Elixir `~> 1.14`.

## [0.11.0] - 2026-05-21

0.11.0 reshapes the conditional-compilation config introduced in 0.10.0
around a new value space — `true | false | :purge` per kind — and adds two
new features that compose on top of it: runtime toggling without
recompilation, and per-module overrides.

### Breaking changes (minor)

- **`config :bond, <kind>: false` no longer compiles contracts out.** It
  now means "compiled in, runtime guard defaults to off." If you used
  `false` in 0.10.0 to get zero-overhead behaviour, change it to `:purge`
  to preserve that behaviour. `true` continues to work as before (with the
  addition of runtime toggleability — see below).

### Added

- **`:purge` mode for each contract kind.** Setting any of `:preconditions`,
  `:postconditions`, or `:checks` to `:purge` causes Bond to emit no code
  for that kind. The resulting BEAM contains no contract logic; per-call
  overhead is zero. Contract documentation for that kind is also
  suppressed.

- **Runtime toggling.** When a kind is compiled with `true` or `false`, the
  emitted override carries a runtime guard:
  `Application.get_env(:bond, <kind>, <compile_time_value>)`. The contract
  is evaluated unless the runtime value is exactly `false`. Operators can
  flip contracts on or off via `Application.put_env/3` from a remote
  console — no recompilation needed. The compile-time value sets the
  default for the runtime guard.

  Benchmark on the project fixture (`bench/runtime_check_overhead.exs`,
  trivial `@pre is_number(x)` in a tight loop): `:purge` ~48 ns/call,
  `false` ~89 ns/call (~40 ns guard overhead), `true` ~155 ns/call (guard
  plus assertion eval).

- **`:overrides` config for per-module rules.** A list of
  `{Module | Regex, opts}` tuples. Module-atom keys match exactly; `Regex`
  keys match against the source-visible module name (no `Elixir.` prefix).
  Use this to opt specific modules in or out of contract compilation
  without touching their source. Example:

      config :bond,
        preconditions: true,
        overrides: [
          {MyApp.HotPath, preconditions: :purge, postconditions: :purge},
          {~r/Workers\\./, postconditions: false}
        ]

- **`use Bond, opts` per-module options.** Pass any of `:preconditions`,
  `:postconditions`, `:checks` directly at the `use` site to override
  global and `:overrides` settings for that module.

      defmodule MyApp.HotPath do
        use Bond, preconditions: :purge, postconditions: :purge
      end

  Precedence: `use Bond` opts > exact-atom `:overrides` match > first
  `Regex` `:overrides` match > global config.

- **`Bond.Compiler.resolve_config/3`** — internal helper exposed for
  testing that combines global config, `:overrides`, and `use Bond` opts
  into the final per-module mode map.

### Changed

- `Bond.Compiler.AnnotatedFunction.apply_contract/2` now expects each kind
  in the config map to be `true | false | :purge` rather than a boolean.
  The function returns `nil` when both kinds resolve to `:purge`; in all
  other cases it emits the override with the appropriate runtime guards.

- `Bond.check/1,2` now expands to a runtime-guarded call when the resolved
  `:checks` mode is `true` or `false`, and to `:ok` (a compile-time no-op)
  when the mode is `:purge`.

### Requirements

- Unchanged. Elixir `~> 1.14`.

## [0.10.0] - 2026-05-21

The headline feature of 0.10.0 is **conditional compilation** of contracts.
You can now compile some or all of your contracts out entirely via
application config, with zero per-call overhead for disabled contracts. The
release also adds an ExUnit helper module, polishes error reporting, and
substantially rewrites the user-facing documentation.

### Added

- **Conditional compilation via `:bond` application config.** Three keys,
  read at compile time via `Application.compile_env/3`:
  - `:preconditions` (default `true`) — when `false`, no precondition
    evaluation is emitted in override clauses, and the auto-generated
    `#### Preconditions` doc section is omitted.
  - `:postconditions` (default `true`) — same for postconditions.
  - `:checks` (default `true`) — when `false`, every `check/1,2` macro
    call in modules that `use Bond` expands to `:ok` and the wrapped
    expression is **not evaluated**. (Don't put side effects inside
    `check`.)

  When both `:preconditions` and `:postconditions` are disabled for a
  function, Bond emits no override at all. The function runs exactly as
  written, with zero per-call overhead. The function's auto-generated
  contract docs are also suppressed in that case.

  See the new "Conditional compilation" section in the `Bond` moduledoc.

- **`Bond.Test` module** with `assert_precondition_violation/2`,
  `assert_postcondition_violation/2`, and `assert_check_violation/2`
  macros for testing contract violations in ExUnit. Field expectations
  (`:label`, `:expression`, etc.) can be exact values or `Regex` patterns.

- **New `guides/faq.md`** answering the questions that come up most: why
  contracts when I have ExUnit, will contracts slow down prod, how does
  Bond compare to Norm, what does Bond do that typespecs don't, the
  Assertion Evaluation rule, default-arg behaviour, multi-clause handling.

### Changed

- **Assertion failure messages pretty-print the captured `binding/0`** with
  `inspect/2 ... pretty: true, limit: 20, printable_limit: 200, width: 80`,
  so small bindings stay compact and large structs no longer dominate the
  failure output.

- **Stack traces of raised assertion exceptions are pruned** to omit
  `Bond.*` frames. Failures point at the user's call site rather than
  into `Bond.Runtime.Eval`.

- **`Bond` moduledoc / README restructured.** Leads with a five-line
  `Account.withdraw` example and a one-paragraph elevator pitch. The
  Wikipedia quote moves out. Assertion syntax recommends the keyword-list
  form as primary. New `Conditional compilation` section. The `Math.sqrt`
  example remains as the "showing everything" sample.

- **`guides/getting-started.md` expanded** into a step-by-step walkthrough:
  first `@pre`, postcondition with `result`, labelled assertions,
  predicates, `old` expressions, inline checks, disabling in prod, and
  ExUnit integration.

### Internal

- New private function in `Bond.Runtime.Eval` that prunes Bond frames from
  the captured stack trace before raising.
- `Bond.Compiler.AnnotatedFunction.apply_contract/1` is now
  `apply_contract/2` taking a `contract_config` map.
  The `__before_compile__/1` callback reads the config from a
  `@__bond_contract_config__` module attribute set by Bond's `__using__/1`.

### Requirements

- Unchanged. Elixir `~> 1.14`.

## [0.9.1] - 2026-05-21

A patch release covering documentation cleanup left over from the 0.9.0
refactor plus a handful of usability improvements.

### Added

- `.formatter.exs` is now published with the Hex package and declares
  `locals_without_parens` for `check/1`, `check/2`, and `old/1`. Downstream
  projects can pick these up with `import_deps: [:bond]` in their own
  `.formatter.exs`.
- Assertion-failure messages now include an `at: <file>:<line>` line so the
  source location is clickable in editors.

### Changed

- `binding/0` captured in assertion-failure info is sorted by name so
  failure messages are reproducible across runs.

### Fixed

- README/moduledoc no longer references the removed Bond.def/2 and
  Bond.defp/2 macros, eliminating `mix docs` cross-reference warnings.
- The `getting-started` guide installation hint now references the current
  version.
- CHANGELOG no longer auto-links the removed `define_function_with_contract/4`
  helper.

### Internal

- Removed the vestigial `:context` field from `Bond.Compiler.Assertion`.
- Tightened the `Bond.Compiler.AnnotatedFunction` moduledoc.

## [0.9.0] - 2026-05-21

This release is a large internal refactor with no breaking changes to the
public API. `@pre`, `@post`, and `check/1,2` all behave the same as in 0.8.x.

### Changed

- **Bond no longer overrides `Kernel.def/2` and `Kernel.defp/2`.** Contracts
  are now applied via Elixir compiler hooks (`@on_definition`,
  `@before_compile`, `@after_compile`). This makes Bond more robust against
  changes in Elixir's macro expansion semantics, eliminates a class of
  macro-hygiene issues, and plays nicer with other macros that produce
  function definitions.
- **Multi-clause functions are now wrapped by a single override clause that
  delegates to `super/1`** rather than having contract logic inlined into
  each clause. Elixir's normal pattern matching handles dispatch inside the
  `super` call.
- **Assertion failures are signalled by a throw / catch** instead of being
  raised inline. Each `@pre`/`@post` group compiles to an anonymous function
  that throws `{:assertion_failure, info}` on the first failure;
  `Bond.Runtime.Eval` catches it and raises the appropriate exception type.
- Functions with contracts now get auto-generated `Preconditions` and
  `Postconditions` sections in their documentation even if the user did not
  attach a `@doc` themselves. Previously contract documentation was only
  emitted when a `@doc` was present.
- Internal modules are reorganised into `Bond.Compiler.*` (compile-time) and
  `Bond.Runtime.*` (run-time) namespaces.

### Internal

- New modules: `Bond.Compiler.AnnotatedFunction` (multi-clause function
  model), `Bond.Compiler.FunctionDefinition`, `Bond.Compiler.CompileStateFSM`
  (rewritten), `Bond.Runtime.Eval`.
- Removed internal modules `Bond.Compiler.AnnotatedFunctionClause` and
  `Bond.Compiler.LegacyCompileStateFSM`, along with the
  `define_function_with_contract/4` helper they used.
- `Bond.Compiler.Assertion` now carries a stable random `:id` for use in
  error reporting and future internal tooling.

### Requirements

- Unchanged. Elixir `~> 1.14`.

## [0.8.3] - 2024-11-08

Released before this changelog was established. See the git history for
details.