Browser-Facing Output

GOWDK does not compile arbitrary Go or JavaScript for the browser by default. The current browser-facing output slices are:

• Partial form enhancement runtime emitted as assets/gowdk/gowdk.js.
• Generated JavaScript islands for stateful components.
• Component-level WASM island asset emission for components that declare @wasm, with g:island="wasm" still supported as a call-site override.

Partial Runtime

When a page uses a fragment-producing action form with g:target and g:swap, SPA builds emit the client runtime:

<form g:post={Refresh} g:target="#patients" g:swap="innerHTML">
  <input name="query" />
  <button>Refresh</button>
</form>

The compiler lowers this to normal form attributes plus data-gowdk-* metadata and emits a deferred script tag for assets/gowdk/gowdk.js.

The runtime:

• Submits enhanced forms with X-GOWDK-Partial, X-GOWDK-Target, and X-GOWDK-Swap headers.
• Applies innerHTML or outerHTML swaps.
• Reloads the current page when the response carries X-GOWDK-Reload: 1.
• Dispatches gowdk:before-request, gowdk:after-swap, and gowdk:request-error. Failed enhanced requests include response status, body, and response in event detail when available.
• Toggles aria-busy on the submitting form.
• Restores focus by matching the active element's id or name when possible.
• Calls generated island destroy and mount hooks around replaced island DOM.

JavaScript Islands

Stateful components use generated JavaScript by default:

@component Counter

import ui "github.com/acme/app/ui"

state ui.CounterState = ui.NewCounterState()

client {
  fn Increment() {
    Count++
  }
}

view {
  <button g:on:click={Increment()}>{Count}</button>
}

The compiler validates a small Go-like client subset and emits browser JavaScript under assets/gowdk/islands/.

Supported island syntax is documented in docs/language/syntax.md, docs/language/markup.md, and docs/language/components.md. The subset includes scalar handler parameters, scalar locals, field assignment, increment/decrement, arithmetic, comparisons, boolean logic, conditional expressions, computed values, lifecycle/effect blocks, refs, simple bindings, conditionals, keyed list rendering, and compiler-owned list/string/numeric built-ins.

Unsupported today:

• Arbitrary Go syntax in the browser.
• Arbitrary JavaScript.
• Loops in client handlers.
• Event object reads.
• Broad date/time/browser APIs.
• Recursive helper functions.
• User-defined browser runtime imports.

Component-Level WASM Islands

Components declare WASM at the component level:

@component Counter
@wasm ./browser/counter

view {
  <button>Counter</button>
}

<Counter />

When @wasm points to a local package, GOWDK builds that package with GOOS=js GOARCH=wasm. The package must be browser-safe and cannot import server/process/network packages such as net/http, os/exec, database/sql, raw syscall, plugin, or unsafe. Declared Go WASM island packages also ship assets/gowdk/islands/wasm_exec.js; the generated component loader first tries a direct WASM instantiate path and falls back to Go runtime imports when a compiled Go module needs them.

Declared browser-side Go packages must produce a browser WASM module and export the component-scoped ABI entrypoints:

//go:wasmexport GOWDKMountCounter
func GOWDKMountCounter() uint32 { return 0 }

//go:wasmexport GOWDKHandleCounter
func GOWDKHandleCounter() uint32 { return 0 }

//go:wasmexport GOWDKDestroyCounter
func GOWDKDestroyCounter() uint32 { return 0 }

The generated loader passes a bootstrap object containing component name, state, props, emits, refs, and compiler-owned binding metadata. Returned patch lists may use setText, setAttr, removeAttr, toggleClass, setStyle, setHidden, replaceList, and emit; unsupported patch operations are rejected with a console error. Missing required exports and startup failures are reported to the browser console instead of silently disabling the island.

Normal calls to a component with @wasm use the WASM island runtime. If a component is called with g:island="wasm" and no @wasm package is declared, GOWDK emits the current placeholder module plus loader shape.

Production Mode

Build.Mode affects generated island assets:

Build: gowdk.BuildConfig{
	Mode: gowdk.Production,
	Output: "dist/site",
}

Development mode emits JavaScript island source maps. Production mode omits .js.map artifacts and sourceMappingURL comments and trims formatting-only whitespace from generated island JavaScript.