Crate mf2_build 

mf2-build — a directory of translated message resources to what an application ships: the manifest, one catalog per locale, and a generated Rust module.

It runs from the build.rs of the crate that includes the generated module — fn main() { mf2_build::run(); }, which reads mf2’s features through links (run) — and from mf2-cli, reading the same Config both times so that the two can never disagree. Nothing here is linked into the client wasm.

locales/<tag>/*.mf2   ─▶ Loader ─▶ records ─▶ mf2-syntax ─▶ models
                                                 │
                                    manifest ◀───┤  ids → MsgId, slots,
                                                 │  markup, functions, hash
                            lints (mf2 check) ◀──┤
                                                 ▼
                                     fallbacks flattened
                                                 ▼
                      locale data sliced ─▶ mf2-catalog writer ─▶ .mf2b + .br/.gz
                                                 ▼
                                      the generated Rust module

What 2.x promises here

What an i18n crate’s build.rs and a tool call: Build and what it returns (Outcome, Published, LocaleInfo, Report, Diagnostic), the mf2.toml it reads (Config and its parts), the client Features, the lints (Lint, Level) and the Error. The pipeline — the modules below, which mf2-cli and the conformance crate reach into — is private or hidden from the documentation, and not promised (docs/versioning.md):

Module	What it does
config	mf2.toml
features	the client feature set, from CARGO_FEATURE_* or --features
loader	a locale’s files to records: .mf2 resources or flat JSON
lint	the names and levels of mf2 check’s lints
corpus	reading and parsing every locale, with errors placed in their files
manifest	ids → MsgId, slots, markup, functions, the hash
check	the lints themselves
slice	the locale data a corpus needs
catalog	one catalog per locale: fallbacks, compression, content hashes
codegen	the generated Rust module
pseudo	the pseudo-locales en-XA and ar-XB
build	Build, which runs all of it

The user guide

The Rust MF2 book is the user guide: how the crates fit together, web and native applications, the command line, and what 2.x promises. An application names this crate in its i18n crate’s [build-dependencies], and mf2 in its [dependencies].

Structs

Build

A build, configured.

CatalogConfig

[catalog].

Config

A corpus’s configuration.

Diagnostic

One thing a build has to say.

Features

Which functions the built catalogs may use, and which locale data they need.

LocaleDataConfig

[locale_data].

LocaleInfo

One locale in the built corpus.

Outcome

What a build produced.

Published

What Outcome::publish did.

Report

Everything a build found, in the order found.

Enums

DataSet

How much of one CLDR table a catalog carries.

Emit

What a build writes (plans/05-tooling.md §4; owner question 1 of plans/12-phase-5a-work-order.md).

Error

What stops a build.

Level

What a lint does when it fires.

Lint

One check mf2 check makes.

Missing

What a locale that lacks a message gets.

Strip

A catalog section a production build leaves out.

Functions

run

Everything a build script does: fn main() { mf2_build::run(); }.

Type Aliases

Result

The result of a build step.