@barefootjs/jinja

Jinja2 adapter for BarefootJS: compiles the BarefootJS IR (JSX → IR, see spec/compiler.md) into .jinja template files plus the client JS bundle every other adapter produces, and ships a Python rendering runtime (python/barefootjs/) that renders those templates through a plain jinja2.Environment — no framework is required (Flask, Django, bare WSGI, etc. all work the same way).

Near-mechanical port of @barefootjs/xslate (the Text::Xslate/Kolon adapter) to Jinja2 syntax. See src/adapter/jinja-adapter.ts's header comment for the full Kolon↔Jinja syntax-mapping table and the JS/Python semantics divergences this port handles uniformly (truthiness, stringification, reserved-word identifier mangling, and the evaluator-only higher-order-callback lowering since Jinja has no lambda expression).

Template output shape

• name: 'jinja', extension: '.jinja', templatesPerComponent: true — one .jinja file per component, named by snake-casing the PascalCase component name (UserCard → user_card.jinja).
• Hydration markers (bf-s, bf-h/bf-m/bf-r, bf-p, slot/conditional comment markers, loop boundary comments) use the SAME runtime method names as every other adapter's bf.* calls (bf.scope_attr(), bf.hydration_attrs(), bf.text_start/text_end, bf.comment(...), …) — see spec/template-helpers.md for the shared helper contract.
• Every text/attribute interpolation of a possibly-non-string value is routed through bf.string(...) (or bf.bool_str(...) for boolean-shaped values); every non-comparison condition position is routed through bf.truthy(...). Both are pure Python-runtime helpers — see the Python runtime pointer below.

Python runtime

python/barefootjs/ is a self-contained Python package (only dependency: jinja2) implementing the engine-agnostic bf object every emitted template calls into: hydration markers, context propagation (provide_context/use_context), child-component rendering (render_child), script registration, and the JS-compatible helper library (string, bool_str, truthy, number, floor/ceil/round, array/string helpers, the *_eval evaluator helpers, spread_attrs, query, …). It mirrors the layering of packages/adapter-perl/lib/ (an engine-agnostic core plus a thin per-engine backend) — see spec/template-helpers.md for the semantic contract each helper must satisfy, and the package's own tests under python/tests/.

Usage

// vite.config.ts
import { defineConfig } from 'vite'
import { barefoot } from '@barefootjs/jinja/vite'

export default defineConfig({
  plugins: barefoot({
    components: ['./src/components'],
    templates: './dist/templates',
  }),
})

vite build then emits .jinja templates + client JS under templates / Vite's own build.outDir. A Python host renders a component by constructing a jinja2.Environment (with autoescape=True, undefined=barefootjs.JsUndefined, trim_blocks=True, lstrip_blocks=True — see the adapter header comment for why the last two are required) over a FileSystemLoader pointed at the emitted templates, wiring in barefootjs.backend_jinja as the render backend. JinjaBackend(paths=[...]) builds exactly that Environment.

JS undefined and null are two values: host None is JS null, and barefootjs.UNDEF (a JsUndefined) is JS undefined. To leave a prop unset, omit its key (an omitted prop takes its destructure default, or reads as undefined); pass UNDEF for a prop that is present and undefined. A prop passed as None is null: its default does not apply.