Component signatures

A component's authored parameter list is its Go signature and its markup contract. gsx emits no props wrapper type.

Choose a signature shape

Shape	Declaration	Use it when
Loose parameters	component Card(title string, count int)	The component has a small, direct API.
Options value	component Panel(opts PanelOptions)	A long-lived or high-arity Go API benefits from an author-owned struct.
Nullary	component Divider()	The component needs no call-site data.
Callable value	func(attrs gsx.Attrs) gsx.Node	A package function or factory-produced value should be tag-callable.

Method receivers are not component inputs. Parameters keep their authored order for direct Go callers; markup binds ordinary parameters by exact name.

package views

import "github.com/gsxhq/gsx"

component Button(variant string, children gsx.Node, attrs gsx.Attrs) {
	<button class={ "btn", variant } { attrs... }>{ children }</button>
}

component Page() {
	<Button variant="primary" data-test="save">Save</Button>
}

Renders:

<button class="btn primary" data-test="save">Save</button>

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Button is emitted as func Button(variant string, children gsx.Node, attrs gsx.Attrs) gsx.Node. Go callers pass those values directly.

Exact-name inputs

An ordinary markup attribute fills a parameter only when its name exactly matches the authored identifier. Matching is case-sensitive and does not convert kebab names or struct fields.

package views

type Props struct {
	Title string
}

component Greeting(name string) {
	<p>Hi { name }</p>
}

component Card(title string, n int) {
	<div>{ title }: { n }</div>
}

component Panel(p Props) {
	<section>{ p.Title }</section>
}

component Page() {
	<>
		<Greeting name="Ann"/>
		<Card title="T" n={2}/>
		<Panel p={Props{Title: "P"}}/>
	</>
}

Renders:

<p>Hi Ann</p><div>T: 2</div><section>P</section>

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• <Greeting name="Ann"/> fills name.
• <Panel p={Props{Title: "P"}}/> passes one ordinary composite value.
• An ordinary parameter can be filled at most once on a call.
• title does not address a field inside p; declare title as a separate parameter if callers should fill it separately.
• data-*, aria-*, hx-*, and other non-identifier names always contribute to attrs.

Omitted ordinary parameters receive their Go zero value when gsx can express it at the call site. An opaque cross-package type whose zero cannot be named must be supplied explicitly; gsx reports a positioned required-input diagnostic.

Author-owned options structs

Use an ordinary struct parameter when keyed Go construction is valuable:

type CardOptions struct {
	Title    string
	Featured bool
}

component Card(opts CardOptions) {
	<article class={ "featured": opts.Featured }>{opts.Title}</article>
}

component Page() {
	<Card opts={CardOptions{Title: "News", Featured: true}}/>
}

The struct is entirely application-owned. gsx does not inspect its fields or derive a second markup API from them.

Forward values explicitly

Pass an assembled value through the target parameter's exact name.

package views

type cardData struct {
	Title string
}

type pageData struct {
	Heading string
}

type Home struct{}

component Card(d cardData) {
	<div>{ d.Title }</div>
}

component Page(d pageData) {
	<Card d={cardData{Title: d.Heading}}/>
}

component (p Home) Content(pd pageData) {
	<h1>{ pd.Heading }</h1>
}

component (p Home) Shell(pd pageData) {
	<p.Content pd={pd}/>
}

Renders:

<h1>Hi</h1>

▶ Open in Playground

<p.Content pd={pd}/> is ordinary named input binding. {bag...} on a component always means an attrs contributor, never struct destructuring.

Tag-callable Go values

A package-level function or value is tag-callable when gsx can resolve a concrete function signature returning gsx.Node. Parameter names are part of the markup contract, including the reserved attrs role:

package views

import "github.com/gsxhq/gsx"

component icon(name string, attrs gsx.Attrs) {
	<span class="icon" data-name={name} {attrs...}>i</span>
}

func namedIcon(name string) func(attrs ...gsx.Attr) gsx.Node {
	return func(attrs ...gsx.Attr) gsx.Node {
		return icon(name, gsx.Attrs(attrs))
	}
}

var HomeIcon = namedIcon("house")

component Toolbar() {
	<HomeIcon class="text-blue" aria-label="Home"/>
}

The supported attrs types are gsx.Attrs, []gsx.Attr, a defined slice with underlying type []gsx.Attr, and ...gsx.Attr. A differently named attrs-shaped parameter is an ordinary input; a non-reserved variadic is Go-callable but not markup-bindable. Since Go allows only one final variadic parameter, use non-variadic attrs gsx.Attrs when a signature also has variadic children.

Reserved component inputs

Name	Role
ctx	Ambient render context; it is not declared as a component parameter.
children	Body input; declare children gsx.Node or children ...gsx.Node.
attrs	Ordered fallthrough input; declare one of the supported attrs-bag types.

children and attrs are special only in lowercase. Parameters named Children or Attrs are ordinary exact-name inputs. A component without children rejects a non-empty body, and a component without attrs rejects every unmatched attribute or attrs contributor.

Names beginning _gsx are reserved for generated implementation details.