feat(compiler): add experimental $provideTypeInfo provider and program.getTypeInfo API

[Timothee Guerin (timotheeguerin)]

Fixes #1993
Fixes #4860 (http specific info)

Summary

Adds a new experimental $provideTypeInfo library provider 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, a provider:

• 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-provider compiler feature flag, scoped to the package declaring it: a library opts in via its own tspconfig.yaml and consumers do not need to enable anything.

export const $provideTypeInfo = defineTypeInfoProvider(({ program, target }) => {
  if (target.kind !== "Operation") return undefined;
  return { content: "extra info about this operation" };
});

[pkg-pr-new]

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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: 36ec24a

[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 $provideTypeInfo library provider and program.getTypeInfo(type) API allowing libraries to contribute extra, domain-specific information about types. Unlike the $onValidate lifecycle hook, a provider 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).,> ,> Providers are gated by the type-info-provider 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 `defineTypeInfoProvider` for typing):,> export const $provideTypeInfo = defineTypeInfoProvider(({ 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 a $provideTypeInfo 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

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[Copilot]

Pull request overview

Adds a new experimental “type info” contribution mechanism so TypeSpec libraries can lazily provide extra domain-specific markdown (e.g., HTTP route details) for IDE hover/tooling via a new program.getTypeInfo(type) API, gated behind a per-library compiler feature opt-in.

Changes:

• Introduces $provideTypeInfo discovery/registration in the compiler (feature-gated), plus Program.getTypeInfo to query merged provider output.
• Extends the language server hover details to append contributed info (with a horizontal rule separator) and adds comprehensive compiler/server tests.
• Implements an @typespec/http provider that surfaces resolved HTTP route + response status codes, adds docs, and ensures bundling/publishing preserves per-library tspconfig.yaml feature opt-ins.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
website/src/content/docs/docs/extending-typespec/providing-type-info.md	New documentation for authoring and consuming $provideTypeInfo contributions.
website/src/content/current-sidebar.ts	Adds the new doc page to the sidebar with an “experimental” badge.
packages/http/tspconfig.yaml	Opts @typespec/http into the type-info-provider feature for provider registration.
packages/http/test/type-info.test.ts	Tests HTTP provider output and verifies real compiler registration via program.getTypeInfo.
packages/http/src/type-info.ts	Implements $provideTypeInfo for HTTP operations (route + response status codes).
packages/http/src/tsp-index.ts	Exports $provideTypeInfo from the library entry point.
packages/http/package.json	Ensures tspconfig.yaml is shipped so the per-library opt-in survives publishing.
packages/compiler/test/type-info-provider.test.ts	Compiler-level tests for merging, gating, and error handling of providers.
packages/compiler/test/server/get-hover.test.ts	Language-server hover tests verifying appended info and separator behavior.
packages/compiler/test/server/completion.tspconfig.test.ts	Updates config completion to include type-info-provider and its description.
packages/compiler/test/core/cli/actions/info.test.ts	Updates tsp info feature listing output to include type-info-provider.
packages/compiler/src/server/type-details.ts	Appends contributed type info to symbol details/hover output.
packages/compiler/src/index.ts	Exports defineTypeInfoProvider and related TypeInfo* types from public API surface.
packages/compiler/src/core/types.ts	Defines TypeInfo, TypeInfoContext, and TypeInfoProvider types.
packages/compiler/src/core/program.ts	Adds provider registration and getTypeInfo implementation with design-time crash handling.
packages/compiler/src/core/library.ts	Adds defineTypeInfoProvider typing helper.
packages/compiler/src/core/features.ts	Registers the type-info-provider compiler feature with a description.
packages/compiler/src/core/external-error.ts	Extends ExternalError to support $provideTypeInfo crash reporting.
packages/compiler/src/core/binder.ts	Discovers $provideTypeInfo exports and registers them when feature is enabled per declaring project/library.
packages/bundler/src/bundler.ts	Bundles a library’s tspconfig.yaml so per-library feature opt-ins persist in browser bundles.
.chronus/changes/provide-type-info-http-route-2026-7-30-12-30-0.md	Changelog entry for @typespec/http type info provider.
.chronus/changes/provide-type-info-2026-7-30-12-30-0.md	Changelog entry for compiler API/hook introduction.
.chronus/changes/on-info-bundler-tspconfig-2026-7-31-9-30-0.md	Changelog entry for bundler preserving tspconfig.yaml in bundles.

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[Copilot]

Pull request overview

Copilot reviewed 23 out of 23 changed files in this pull request and generated no new comments.

Suppressed comments (2)

Previously missed (2) — in code that hasn't changed since the last review.

packages/compiler/src/core/program.ts:337

• getTypeInfo reuses the same context object for all providers. A misbehaving provider could mutate context (e.g. replace target) and affect subsequent providers, producing incorrect merged results. Passing a fresh context object per provider prevents cross-provider interference at minimal cost.

      const context: TypeInfoContext = { program, target };
      for (const provider of typeInfoProviders) {
        let result: TypeInfo | undefined;
        try {
          result = provider.callback(context);

packages/http/src/type-info.ts:19

• getHttpOperation always returns an HttpOperation as the first tuple element, so the if (!operation) branch is dead code and implies operation can be undefined when it cannot. This also prevents TypeScript from helping catch real nullability issues.

  const [operation] = getHttpOperation(program, target);
  if (!operation) {
    return undefined;
  }

[iscai-msft]

ooh looks great!