writeonce/docs/examples/shop

shop — the writeonce program template

A small store you can buy from, structured the way a real writeonce web app should be. Copy this directory to start a new app; every file has one concern, and the module system (one directory = one module, pub = the export line) enforces the separation the layout promises.

Run it

cd docs/examples/shop
woc . && WO_DATA=./data ./target/shop 8080     # durable store
./target/shop 8080                             # RAM-only (dev)

Browse http://127.0.0.1:8080/ — products → product page → buy (stock checked and decremented) → confirmation → /orders. With WO_DATA, kill it and restart: the orders are still there (WAL replay).

The template builds and runs as written — the two [deps] resolve, the seed lands, and every route answers.

The view form

A render() body is one backtick raw text literal. Markup is markup: real newlines, real double-quoted attributes, and the method's source indentation removed at compile time, so the served bytes carry the markup's own nesting and not the code's.

fn render() -> Text {
  return `
    <div class="card">
      <h3><a href="/p/{{ self.sku }}">{{ self.name }}</a></h3>
      <p class="price">€ ${self.price}</p>
      ${stock}
    </div>`;
}

Every render() makes its class a component — wo-html's structural Component interface, satisfied by having the method, never declared. Parent components hold children directly (cards: multi Component) and render them with render_all, so ProductListPage knows nothing about ProductCard beyond render(). The document itself is a component too: AppShell { title, content } in layout/app.wo, which links a real stylesheet rather than inlining one — that is why it is its own shell and not wo-html's Layout.

Two holes, and the difference is the whole escaping story:

• {{ expr }} HTML-escapes — it compiles to a call to the esc in scope (wo-html's, unless the app declares its own). Display data goes here; a typo'd field is a compile error, not a broken page.
• ${ expr } is raw — for markup you built yourself, like the ${stock} fragment above or ${content} in the app shell.

Nothing is parsed at request time. The literal is a compile-time form: it produces exactly the string constant and concatenation chain the old hand-written version did, so there is no template engine to ship, warm up, or sandbox.

The file map (Angular equivalents)

this template	concern	Angular analog
types.wo	MODEL — @table classes ARE the WAL database	models/*.ts (+ the entire database)
layout/app.wo	app shell: document, header+footer composition, ok_html/html_error transport helpers	app.component.html
layout/header.wo / footer.wo	shared chrome fragments	header.html / footer.html
product_list/view.wo	VIEW — classes with fn render() -> Text, fields = exactly what is displayed	product-list/view.html
product_list/controller.wo	CONTROLLER — query the model, fill the view, answer a Resp; beside its view in the same module	component .ts + service
product_page/, orders/	one module per feature: view.wo + controller.wo	feature folders
static_files/controller.wo	/assets/* from disk, traversal-safe, typed	angular.json assets
assets/style.css	ONE real stylesheet, sectioned per feature	the .scss files
the render() bodies	ONE raw text literal each: real newlines, real double-quoted attributes, source indentation removed at compile time, ${} raw holes and {{ }} auto-escaping ones	Vue <template> (in-SFC)
layout/app.wo → AppShell	the document, as a two-slot component	app.component.html
main.wo	bootstrap: seed, routes, serve — nothing else	app-routing.module.ts + main.ts

Separation is compiler-enforced: one feature = one directory = one module, holding that feature's view AND its controller. A module sees only its own declarations plus what it uses, so a controller reaching into another feature has to say so. The @table classes sit in types.wo at the root and are reachable from every feature module without export — see gap #1 below for why that is not the contradiction it looks like.

What is deliberately different (doctrine)

• Templates compile or they don't exist (story 37). See The view form above: the markup is a compile-time literal, never a file parsed per request. Gap #3 ("the language has NO multi-line expression or literal", recorded while writing this template) is CLOSED — the raw literal landed with story 37's compiler slice, and this directory was its consumer. Styles stay a real CSS file, served statically (there is no scss preprocessor).
• No closures, no DI. A view is a class with fields + render() (wo-html's Component); a controller is a class satisfying Handler. Capture = a field.
• The MVC seam is enforced by where the query sits. Controllers hold every from … select; a view receives VALUES — for the list page, a multi Component of already-filled cards. No view in this template touches the database, and wo-html contains no query at all.
• No sessions/cart yet. Buying is per-product (qty → order). A cart needs a session story that does not exist yet.
• No client-side JS. Every interaction is a form round trip.
• pub + @table cannot combine (recorded gap #1) — and it does not matter. pub in front of an annotated class is a parse error (WO-E101), but no @table needs it: a CLASS is reachable across module lines without being exported. Verified 2026-08-25 by building and running all three shapes — a feature module querying a root @table, a feature module using a root plain class, and an @table declared inside a types/ module and queried from the root. What IS module-scoped is a free fn (WO-E210), so a query shared by two features belongs on a class as a static fn. An earlier revision of this file claimed the gap forced controllers into the root module and made a types/ module impossible; both were wrong, and the layout below is what the language actually allows.
• @view projection classes (recorded gap #2): today controllers copy row fields into view classes by hand. The wished-for form — class ProductCard @view { ... } filled by from p in Product select p.name, p.price — needs projection queries; recorded, not worked around.

Judging the DX — what to look at

1. types.wo — the entire persistence layer is 20 lines.
2. orders.controller.wo — the whole buying flow (validate, stock check, decrement, durable insert, render) with no framework magic.
3. orders/view.wo — the referendum, now answered: three render() bodies, each one literal, no concatenation and no esc() calls, and OrdersPage holding its rows as child components.
4. main.wo — the app at a glance: five routes, one middleware, serve.