feat(compiler): add experimental $onInfo hook and program.getTypeInfo API

[timotheeguerin]

Fixes #1993

Summary

Adds a new experimental $onInfo library hook and program.getTypeInfo(type) API that lets libraries contribute extra, domain-specific information about types. This information is surfaced in IDE hover tooltips and can be queried programmatically by tooling (e.g. AI agents).

Unlike $onValidate, this hook:

• is never run during compilation — it is invoked lazily and on demand.
• must not mutate the type graph — it only reads the program to answer questions about a type.

The feature is gated behind a new type-info-hook compiler feature flag.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@typespec/bundler@11489

npm i https://pkg.pr.new/@typespec/compiler@11489

npm i https://pkg.pr.new/@typespec/http@11489

commit: bfd1778

[github-actions]

All changed packages have been documented.

• ✅ @typespec/bundler
• ✅ @typespec/compiler
• ✅ @typespec/http

Show changes

@typespec/bundler - fix ✏️

Include a library's own tspconfig.yaml in the generated bundle so per-library opt-ins (such as compiler features) are preserved when the library is loaded in the browser (e.g. in the playground).

@typespec/compiler - feature ✏️

Add a new experimental $onInfo library hook and program.getTypeInfo(type) API allowing libraries to contribute extra, domain-specific information about types. Unlike $onValidate, this hook never runs during compilation and must not mutate the type graph — it is invoked lazily and on demand (e.g. by the language server for hover documentation, or by tooling querying the type).,> ,> The hook is gated by the type-info-hook compiler feature, scoped to the package that declares it: a library opts in via its own tspconfig.yaml and consumers do not need to enable anything.,> ,> ts,> // A library exports a provider (use `defineInfoHook` for typing):,> export const $onInfo = defineInfoHook(({ program, target }) => {,> if (target.kind !== "Operation") return undefined;,> return { content: "extra info about this operation" };,> });,> ,> // Tooling / language server queries it (merges every library's contribution):,> const info = program.getTypeInfo(type);,>

@typespec/http - feature ✏️

Add an $onInfo provider that surfaces the resolved HTTP route (verb and URI template) and response status codes of an operation. This is shown when hovering an operation in the IDE and can be queried programmatically via program.getTypeInfo(operation).,> ,> ts,> const info = program.getTypeInfo(operation);,> // { content: "`HTTP Route`: `GET /pets/{id}`\n\n`Responses`: `204`" },>

[azure-sdk-automation]

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension

[timotheeguerin]

can we add experimental badge to sidebar?

[timotheeguerin]

Done — the sidebar entry is now a SlugItem with badge: { text: "experimental", variant: "caution" } (matching the variant used for alpha/beta libraries).