---
title: September 2023
releaseDate: 2023-09-12
---

:::caution
This release contains **breaking changes**
:::

## New Features

### `@typespec/compiler` New Features

- Allow library authors to precisely define the visibility of operation templates with new decorators `@parameterVisibility` and `@returnTypeVisibility`, paired with corresponding accessor methods `getParameterVisibility` and `getReturnTypeVisibility`.
- Add coloring for documentation comments in Visual Studio and Visual Studio Code language extensions.
- Change yaml parser from `js-yaml` to `yaml`, enabling more precise validation and error reporting in `tspconfig.yaml`
- Added validation to ensure that properties of a derived model (using `extends`) are compatible with the base model indexer.
- Export `CompilerOptions` TypeScript type.
- Report library information when library code crashes during `$onValidate` execution.
- Diagnostics reported on a node with an `id` property will highlight the id instead of the entire node. For example, if a diagnostic is reported on a `model` type, the model name will be highlighted, instead of the entire model definition.

### `@typespec/http` New Features

- Add new helper method `resolveRequestVisibility` which incorporates settings from new core decorators `@parameterVisibility` and `@returnTypeVisibility`. This replaces the deprecated `getRequestVisibility` helper.
- Add new helper method `getDefaultVisibilityForVerb` which returns the default visibility for Http verbs.
- Add validation step to issue a warning when an `operation is` statement does not include route information from the original operation container (`interface` or `namespace`). This helps to prevent unexpected route changes when using operation references.
- Add validation to prevent runtime errors when `OAuth2Auth` is given invalid `OAuth2Flow` arguments.

### `@typespec/json-schema` New Features

- Support decimal scalar types.

### `@typespec/openapi3` New Features

- Allow library authors to override default Http verb visibility in operation declarations.

### `@typespec/protobuf` New features

- Support `omit-unreachable-types` option.
- Automatically convert empty operation parameters into a reference to `google.protobuf.Empty` instead of synthesizing an empty model.

### `typespec-vscode` New features

- Add color definition for `@param` tag in documentation comments

## Bug Fixes

### `@typespec/compiler` Bug Fixes

- Fix issue where specifying a directory using the `--config` command line option would search the parent folder hierarchy looking for `tspconfig.yaml`.
- Fix Stack overflow when a model property references itself.
- Fix compiler crash when using the alias of a namespace that has decorators.
- Fix compiler freeze when an invalid token appears between doc comment and type.
- Fix compiler crash when relating recursive types.
- Fix typo in format error diagnostic.

### `@typespec/openapi3` Bug Fixes

- Fixed issue where parameters marked with visibility \"create\" did not appear in a `PATCH` request body.
- Fixed incorrect usage of `exclusiveMinimum` and `exclusiveMaximum` boolean properties.
- Use `anyOf` instead of `oneOf` for operations with shared routes and different request or response bodies.
- Fix handling of `Record<T>` in `model is` and `model extends` statements.

### `@typespec/versioning` Bug Fixes

- Fixed validation in `@typeChangedFrom` for incorrect versioned references.

## Deprecations

### `@typespec/compiler` Deprecations

- The `@deprecated` decorator has been marked as deprecated. Use `#deprecated` directive instead.

### `@typespec/http` Deprecations

- The `getRequestVisibility` helper function is now deprecated. Use `resolveRequestVisibility` or `getDefaultVisibilityForVerb` instead.

## Breaking Changes

### `@typespec/compiler` Breaking Changes

- A semicolon is now required at the end of augment decorator statements. The formatter was already inserting the semicolon, if omitted. For example:

  ```tsp
  @@doc(MyType.myProperty, "Documentation for myProperty");
  ```
