Language Construct Stability

This table is the per-construct stability and deprecation contract for the experimental 0.x .gwdk language. The diagnostics registry already records a stability tier per diagnostic code (internal/diagnostics/registry.go); this page does the same for the language constructs themselves, so a user or tooling author can tell which syntax is safe to depend on and which is still moving.

It complements, and is pinned by, the machine-checked Conformance Corpus: a Stable or Partial construct should have an accept/ case, and a Planned/Deprecated construct should have a reject/ case asserting the diagnostic code named below.

Status Tiers

Stable: accepted by the current compiler and not expected to change shape within 0.x without a deprecation step.
Partial: accepted for a narrower slice than the final contract; the syntax is real but its capability will grow.
Planned: not accepted as source behavior yet; using it is rejected with the listed diagnostic code so it cannot become accidental behavior.
Deprecated: previously accepted spelling that is now rejected with a migration diagnostic.

The tiers below are the code-level registry lang.ConstructStabilities() (with metadata keywords derived from lang.MetadataKeywords and directives checked against viewparse.SupportedDirectiveNames()). TestStabilityRegistryCoversCodeConstructs asserts the registry covers every keyword and directive in code, and TestStabilityTableMatchesRegistry asserts this page matches the registry, so neither the table nor the registry can drift without failing a test.

Top-Level Blocks

Construct	Tier	Notes
`package`	Stable	Required first declaration.
`import`	Stable	Go import for colocated blocks.
`use`	Stable	Package-scoped component import.
`paths {}`	Partial	Literal `=> { field: "value" }` records only.
`build {}`	Partial	Literal records and no-argument Go calls.
`server {}`	Partial	Request-time server-lane data; requires the SSR addon.
`view {}`	Stable	Markup; see directives below.
`style {}`	Stable	Scoped CSS body.
`client {}`	Partial	Bounded component client language.
`go {}` / `go build {}` / `go server {}` / `go client {}` / `go addon.* {}`	Partial	Colocated Go lanes.
`store` / `props` / `state` / `emits`	Partial	Component contracts.
Unknown top-level block	Planned	Rejected with `unsupported_top_level_block`.

Metadata Keywords

All metadata keywords are Stable. The canonical list is lang.MetadataKeywords.

Keyword	Tier
`page`	Stable
`route`	Stable
`title`	Stable
`description`	Stable
`canonical`	Stable
`image`	Stable
`robots`	Stable
`noindex`	Stable
`preload`	Stable
`prefetch`	Stable
`layout`	Stable
`cache`	Stable
`revalidate`	Stable
`error`	Stable
`guard`	Stable
`css`	Stable
`component`	Stable
`wasm`	Stable
`asset`	Stable

Legacy @-prefixed metadata is Deprecated and rejected with malformed_legacy_metadata.

View `g:` Directives

Supported exact-name directives (the closed set in viewparse.SupportedDirectiveNames()):

Directive	Tier	Notes
`g:if`	Stable	Conditional render. Server-side over a `server {}` field; a client island over state/store. `g:else-if`/`g:else` are client-only chains.
`g:for` / `g:key`	Stable	List render. Server-side over a `server {}` field; a client island over state/store. The lane is inferred from the operand.
`g:bind:value` / `g:bind:checked`	Partial	Two-way bindings.
`g:on:*`	Partial	Event handlers with `.prevent`/`.stop`/`.once`/`.capture`/`.debounce`/`.throttle`.
`g:post` / `g:target` / `g:swap`	Partial	Progressive form/fragment submission.
`g:message:*`	Partial	`required`, `minlength`, `maxlength`, `pattern`.
`g:island`	Partial	`js` or `wasm` island.
`g:command` / `g:query`	Partial	Contract web adapters.
`g:subscribe`	Partial	Realtime presentation-event subscription metadata on query-owned elements.
`g:event`	Partial	Parses to explain backend-owned domain events.
`g:unsafe-html`	Stable	Raw HTML escape hatch; `unsafe_raw_html` is reported.
`g:ref`	Partial	Client reference.
`g:slot`	Partial	Named/scoped slot.
`g:transition`	Partial	CSS class/state hooks for client `g:if` branches and keyed client `g:for` rows.
`g:animate`	Partial	CSS class/state hooks for keyed client `g:for` row moves.

Component calls also accept g:bind:<ExportedState> for exported child state fields. HTML elements remain limited to g:bind:value and g:bind:checked.

View Markup Blocks

Construct	Tier	Notes
`{#await}`	Partial	Client-island async placeholder for `fetchJSON[T](urlExpr)` with pending, `{:then name}`, and optional `{:catch err}` branches.

Planned directives are rejected. They currently surface as the generic parse_error rather than the intended unsupported_markup_directive code; that code lands when markup rejections carry their own code (see Conformance Corpus).

Directive family	Tier	Replacement
`g:window`, `g:document`, `g:body`, `g:head`	Planned	Page metadata or `g:on:*` on elements.
`g:await`, `g:async`	Planned	Use `{#await fetchJSON[T](urlExpr)}` for local island placeholders, or build/load data, actions, APIs, and fragments for server-owned data.
`g:use`, `g:action`, `g:attach`	Planned	`client {}` with `g:ref`.

Foreign template syntax ({#if}, {@html}, and similar) is Planned/Unsupported and likewise currently surfaces as parse_error (intended: unsupported_markup_syntax).

Endpoint Declarations

Construct	Tier	Notes
`act`	Stable	`act <Name> POST "<path>"`; POST only today.
`api`	Stable	`api <Name> <METHOD> "<path>"`; GET/POST/PUT/PATCH/DELETE.
`fragment`	Partial	First-slice partial updates.
`act` block form	Deprecated	`act <name> { ... }`; rejected with `old_action_block_syntax`.
`api` block form	Deprecated	`api <name> { ... }`; rejected with `old_api_block_syntax`.