90 lines
4.8 KiB
Markdown
90 lines
4.8 KiB
Markdown
# go-wasm-web — example app for the gowasm engine
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A runnable example of kjol's **gowasm** engine: author UI **components in pure
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Go**, compiled to **WebAssembly**, with **SSR + hydration**, **Next.js-style
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server components**, layouts, the **`kjol/webui` component kit**, **Tailwind CSS**
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(compiled by kjol's own engine), and a **flash-free, state-preserving hot reload**.
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No custom markup, no JSX — just Go. The engine lives in top-level kjol packages
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(`kjol/go/{vdom,wasmruntime,rsc,wasmdevserver,webui}`); this directory is only the
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app that consumes them.
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## Run it
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```sh
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cd cmd/examples/go-wasm-web
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go run ./server # codegen + SSR + hot reload at http://localhost:8085
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```
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Open http://localhost:8085. `/` and `/about` use the light **public** layout;
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`/chart`, `/server`, **`/data`** (client-side fetching), and **`/kit`** (a UI-kit
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"kitchen-sink" demo of the webui components) use the dark **app** layout. Edit
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any `.go` file and the browser hot-swaps the new wasm **without a full reload or
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a flash**, preserving page state; a build failure shows the Go compiler output
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as an overlay.
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**Data fetching** (`/data`) shows both directions of `kjol/httputil`: the server
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answers `/api/quotes` with `httputil.RespondGob([]Quote)` and the client decodes
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it straight back into `[]Quote` with `httputil.FetchGob` (the same Go type on
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both ends — no JSON); and a **user-entered** GitHub repo (`owner/name`) is
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fetched with `httputil.FetchJSON` into a tagged Go struct. The client HTTP
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transport is `wasmruntime.FetchBytes`, injected once via
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`httputil.SetClientTransport`.
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Styling is **Tailwind**: the dev server (and `build.sh`) run `kjol/cmd/twcss`,
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which scans the Go markup + the `webui` kit for utility classes and compiles
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`css/app.css` → `wwwroot/app.css` with kjol's native Tailwind v4 engine. There is
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**no Bootstrap and no hand-written CSS**. (`build.sh` does a one-off build.)
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## This is a separate module
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`go.mod` here declares its own module (`gowasmweb`) with `replace kjol => ../../..`,
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so the app's `go-chart` dependency (and freetype / x/image) stays out of kjol —
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the engine packages (`vdom`, `wasmruntime`, `rsc`, `wasmdevserver`) are
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**stdlib-only**. `go build ./...` at the kjol root does not descend into this
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nested module; build it from this directory.
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## Layout
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```
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app/ the application — neutral, standalone functions (no central struct)
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pages.go Deps + Shell + App/Public layouts + nav + Counter + pages
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chart.go Chart page (go-chart, renders on both sides)
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kit.go /kit — UI-kit demo page showcasing kjol/webui components
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data.go /data — client fetch: gob from /api/quotes + third-party JSON
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server_counter.go //gowasm:server component (server-only; clicks-over-time chart)
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*.gen.go GENERATED by kjol/cmd/wasmgen (routes, layout dispatch, stubs)
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css/app.css Tailwind entry (@import "tailwindcss" + @theme tokens)
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wasm/ the js/wasm client entry point (main_native.go is a host stub)
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server/ the dev-server main: injects Build/Render/Document into wasmdevserver
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wwwroot/ wasmboot.js (+ generated app.css, wasm_exec.js, app.wasm)
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```
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## How it maps onto the engine (top-level `kjol` packages)
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| Engine package | Role | This app's use |
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| `kjol/vdom` | neutral virtual DOM (native + wasm): `VNode`, builders, `Signal`, `RenderHTML` | pages build `*VNode`; `server` SSRs with `vdom.RenderHTML` |
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| `kjol/wasmruntime` | wasm client runtime: reconcile, `Run`/`Hydrate`, router, fetch, HMR state | `wasm/main.go` calls `Hydrate`/`Run` |
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| `kjol/rsc` | stateless server components over HTTP (gob) | `//gowasm:server` + the generated client stub |
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| `kjol/wasmdevserver` | reusable dev server: SSR, `/rsc`, hot reload, error overlay | `server/main.go` fills a `wasmdevserver.Config` |
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| `kjol/httputil` | gob/JSON responders + typed client fetch (`RespondGob`, `FetchGob`, `FetchJSON`) | the `/data` page + the `/api/quotes` handler |
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| `kjol/cmd/wasmgen` | directive codegen → `app/*.gen.go` | run by `buildWasm` and `//go:generate` |
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The **golden rule** holds: `wasmdevserver` imports no app code. The app injects
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`Build` (how to compile the wasm), `Render` (SSR a route → HTML), and `Document`
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(wrap it in a page) via `wasmdevserver.Config` — the same coupling inversion kjol
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uses elsewhere.
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## Directives (expanded by `wasmgen` at build time)
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```go
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//gowasm:page / static layout=public // a route; `static` SSRs it, `layout=` wraps it
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func HomePage(d Deps) func() *VNode { ... }
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//gowasm:layout public // chrome for pages that opt into layout=public
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func PublicLayout(d Deps, content *VNode) *VNode { ... }
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//gowasm:server // runs on the server; calling it looks identical
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func ServerCounter() func() *VNode { count := NewSignal(0); ... }
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```
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