example

fluent_bundle example

A console tour exercising every core capability — the syntax barrel (parse, spans, junk recovery, unescape), the bundle (arguments, attributes, terms, selectors), the NUMBER / DATETIME builtins, bidi isolation, the pseudo-localization transform, custom functions, inert errors, hot reload, locale fallback chains, and the markup span tree. Everything renders through the spec-fallback FluentBackend, so the tour runs anywhere dart runs — no CLDR data, no native build, no setup.

Run

# from the package root
fvm dart run example/main.dart

Tests

# from the package root
make test-example

# or directly
fvm dart test test/example

The test runs this exact showcase and pins every output line, so every claim in the tour is proven on every run — including the invisible ones (the FSI/PDI bidi-isolation marks are asserted as \u2068 / \u2069 escapes). The suite is two-world: it also runs in real Chrome as part of make test-web.

What's inside

Ten sections, one per capability area:

Section	Surface	What it covers
Parse	package:fluent_bundle/syntax.dart	FluentParser → spanned AST, attached comments, junk recovery for bad syntax, unescapeFluentString
Bundle	FluentBundle	hasMessage / getMessage, argument substitution, attribute access, terms
Selectors	select expressions	Exact-number keys (always match), string keys, *[other] defaults — and why [one] is the backend's job
Builtins	NUMBER / DATETIME	Digit options honored locale-blind (minimumFractionDigits, significant digits), ISO-8601 dates
Bidi + transform	useIsolating, transform	FSI/PDI wrapping of substituted values; pseudo-localization of author text only
Custom functions	FluentFunction	A user-supplied STRLEN() callable from FTL
Errors	FluentError out-lists	Missing variable, missing message, reference cycle, parse junk — output always comes back, errors land in the caller's list
Hot reload	addResource(allowOverrides:)	Duplicates rejected by default; overrides replace in place
Locale chain	FluentBundle.locales	The priority-ordered fallback chain the app negotiated
Markup	package:fluent_bundle/markup.dart	formatMessageAsSpans → walkable FluentSpan tree, tag attributes, the standalone parseFluentMarkup

One file on purpose

The whole tour lives in main.dart because pub.dev renders that file as the package's Example tab — splitting it would hide everything else from that page.

Backend-blind on purpose

The core never renders CLDR. Plurals classify as other, numbers are digit-correct but locale-blind, dates are ISO-8601 — that IS the Fluent spec fallback. Swap in IcuBackend (fluent_icu) or IntlBackend (fluent_intl) and every message in this tour renders locale-aware without changing a line of FTL.