Rename to package/backend-openapi-utils.

Signed-off-by: Aramis Sennyey <sennyeya@amazon.com>
2023-03-20 10:31:46 -04:00
parent f14d03d08a
commit 1f5800ae6d
15 changed files with 2 additions and 2 deletions
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Common functionalities for the openapi-router plugin.
+ *
+ * @packageDocumentation
+ */
+
+export type { ApiRouter } from './router';
+export * from './types';
@@ -0,0 +1,39 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { Router } from 'express';
+import { core } from './types';
+
+/**
+ * Typed Express router based on an OpenAPI 3.1 spec.
+ * @public
+ */
+export interface ApiRouter<Doc extends core.Spec> extends Router {
+  get: core.RequestMatcher<Doc, this, 'get'>;
+
+  post: core.RequestMatcher<Doc, this, 'post'>;
+
+  all: core.RequestMatcher<Doc, this, 'all'>;
+
+  put: core.RequestMatcher<Doc, this, 'put'>;
+
+  delete: core.RequestMatcher<Doc, this, 'delete'>;
+
+  patch: core.RequestMatcher<Doc, this, 'patch'>;
+
+  options: core.RequestMatcher<Doc, this, 'options'>;
+
+  head: core.RequestMatcher<Doc, this, 'head'>;
+}
@@ -0,0 +1,16 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+export {};
@@ -0,0 +1,209 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Pulled from https://github.com/varanauskas/oatx.
+ */
+
+import { FromSchema, JSONSchema7 } from 'json-schema-to-ts';
+import {
+  ImmutableContentObject,
+  ImmutableOpenAPIObject,
+  ImmutableReferenceObject,
+} from './immutable';
+
+/**
+ * Basic OpenAPI spec with paths and components properties enforced.
+ */
+export type RequiredDoc = Pick<ImmutableOpenAPIObject, 'paths' | 'components'>;
+
+export type PathDoc = Pick<ImmutableOpenAPIObject, 'paths'>;
+
+/**
+ * Get value types of `T`.
+ */
+export type ValueOf<T> = T[keyof T];
+
+/**
+ * Validate a string against OpenAPI path template, {@link https://spec.openapis.org/oas/v3.1.0#path-templating-matching}.
+ *
+ * @example
+ * ```ts
+ * const path: PathTemplate<"/posts/{postId}/comments/{commentId}"> = "/posts/:postId/comments/:commentId";
+ * const pathWithoutParams: PathTemplate<"/posts/comments"> = "/posts/comments";
+ * ```
+ */
+export type PathTemplate<Path extends string> =
+  Path extends `${infer Prefix}{${infer PathName}}${infer Suffix}`
+    ? `${Prefix}:${PathName}${PathTemplate<Suffix>}`
+    : Path;
+
+/**
+ * Extract path as specified in OpenAPI `Doc` based on request path
+ * @example
+ * ```ts
+ * const spec = {
+ *   paths: {
+ *       "/posts/{postId}/comments/{commentId}": {},
+ *       "/posts/comments": {},
+ *   }
+ * };
+ * const specPathWithParams: DocPath<typeof spec, "/posts/:postId/comments/:commentId"> = "/posts/{postId}/comments/{commentId}";
+ * const specPathWithoutParams: DocPath<typeof spec, "/posts/comments"> = "/posts/comments";
+ * ```
+ */
+export type DocPath<
+  Doc extends PathDoc,
+  Path extends PathTemplate<Extract<keyof Doc['paths'], string>>,
+> = ValueOf<{
+  [Template in Extract<
+    keyof Doc['paths'],
+    string
+  >]: Path extends PathTemplate<Template> ? Template : never;
+}>;
+
+export type DocPathTemplate<Doc extends PathDoc> = PathTemplate<
+  Extract<keyof Doc['paths'], string>
+>;
+
+export type DocPathMethod<
+  Doc extends Pick<RequiredDoc, 'paths'>,
+  Path extends DocPathTemplate<Doc>,
+> = keyof Doc['paths'][DocPath<Doc, Path>];
+
+export type MethodAwareDocPath<
+  Doc extends PathDoc,
+  Path extends PathTemplate<Extract<keyof Doc['paths'], string>>,
+  Method extends keyof Doc['paths'][Path],
+> = ValueOf<{
+  [Template in Extract<
+    keyof Doc['paths'],
+    string
+  >]: Path extends PathTemplate<Template>
+    ? Method extends DocPathMethod<Doc, Path>
+      ? PathTemplate<Template>
+      : never
+    : never;
+}>;
+
+export type DocOperation<
+  Doc extends RequiredDoc,
+  Path extends keyof Doc['paths'],
+  Method extends keyof Doc['paths'][Path],
+> = Doc['paths'][Path][Method];
+
+export type ComponentTypes<Doc extends RequiredDoc> = Extract<
+  keyof Doc['components'],
+  string
+>;
+
+export type ComponentRef<
+  Doc extends RequiredDoc,
+  Type extends ComponentTypes<Doc>,
+  Ref extends ImmutableReferenceObject,
+> = Ref extends { $ref: `#/components/${Type}/${infer Name}` }
+  ? Name extends keyof Doc['components'][Type]
+    ? Doc['components'][Type][Name] extends ImmutableReferenceObject
+      ? ComponentRef<Doc, Type, Doc['components'][Type][Name]>
+      : Doc['components'][Type][Name]
+    : never
+  : never;
+
+export type SchemaRef<Doc extends RequiredDoc, Schema> = Schema extends {
+  $ref: `#/components/schemas/${infer Name}`;
+}
+  ? 'schemas' extends keyof Doc['components']
+    ? Name extends keyof Doc['components']['schemas']
+      ? SchemaRef<Doc, Doc['components']['schemas'][Name]>
+      : never
+    : never
+  : { [Key in keyof Schema]: SchemaRef<Doc, Schema[Key]> };
+
+export type ObjectWithContentSchema<
+  Doc extends RequiredDoc,
+  Object extends { content?: ImmutableContentObject },
+> = Object['content'] extends ImmutableContentObject
+  ? SchemaRef<Doc, Object['content']['application/json']['schema']>
+  : never;
+
+/**
+ * From {@link https://stackoverflow.com/questions/71393738/typescript-intersection-not-union-type-from-json-schema}
+ *
+ * StackOverflow says not to do this, but union types aren't possible any other way.
+ */
+export type UnionToIntersection<U> = (
+  U extends any ? (k: U) => void : never
+) extends (k: infer I) => void
+  ? I
+  : never;
+
+export type LastOf<T> = UnionToIntersection<
+  T extends any ? () => T : never
+> extends () => infer R
+  ? R
+  : never;
+
+export type Push<T extends any[], V> = [...T, V];
+
+export type TuplifyUnion<
+  T,
+  L = LastOf<T>,
+  N = [T] extends [never] ? true : false,
+> = true extends N ? [] : Push<TuplifyUnion<Exclude<T, L>>, L>;
+
+export type ConvertAll<T, R extends ReadonlyArray<unknown> = []> = T extends [
+  infer First extends JSONSchema7,
+  ...infer Rest,
+]
+  ? ConvertAll<Rest, [...R, FromSchema<First>]>
+  : R;
+
+export type UnknownIfNever<P> = [P] extends [never] ? unknown : P;
+
+export type ToTypeSafe<T> = UnknownIfNever<ConvertAll<TuplifyUnion<T>>[number]>;
+
+export type DiscriminateUnion<T, K extends keyof T, V extends T[K]> = Extract<
+  T,
+  Record<K, V>
+>;
+
+export type MapDiscriminatedUnion<
+  T extends Record<K, string>,
+  K extends keyof T,
+> = {
+  [V in T[K]]: DiscriminateUnion<T, K, V>;
+};
+
+export type PickOptionalKeys<T extends { [key: string]: any }> = {
+  [K in keyof T]: true extends T[K]['required'] ? never : K;
+}[keyof T];
+
+export type PickRequiredKeys<T extends { [key: string]: any }> = {
+  [K in keyof T]: true extends T[K]['required'] ? K : never;
+}[keyof T];
+
+export type OptionalMap<T extends { [key: string]: any }> = {
+  [P in Exclude<PickOptionalKeys<T>, undefined>]?: NonNullable<T[P]>;
+};
+
+export type RequiredMap<T extends { [key: string]: any }> = {
+  [P in Exclude<PickRequiredKeys<T>, undefined>]: NonNullable<T[P]>;
+};
+
+export type FullMap<T extends { [key: string]: any }> = RequiredMap<T> &
+  OptionalMap<T>;
+
+export type Filter<T, U> = T extends U ? T : never;
@@ -0,0 +1,76 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import core from 'express-serve-static-core';
+import { DocPathTemplate, MethodAwareDocPath, RequiredDoc } from './common';
+import { PathSchema, QuerySchema } from './params';
+import { RequestBodyToJsonSchema } from './requests';
+import { ResponseBodyToJsonSchema } from './responses';
+
+/**
+ * Typed express request handler.
+ */
+type DocRequestHandler<
+  Doc extends RequiredDoc,
+  Path extends DocPathTemplate<Doc>,
+  Method extends keyof Doc['paths'][Path],
+> = core.RequestHandler<
+  PathSchema<Doc, Path, Method>,
+  ResponseBodyToJsonSchema<Doc, Path, Method>,
+  RequestBodyToJsonSchema<Doc, Path, Method>,
+  QuerySchema<Doc, Path, Method>,
+  Record<string, string>
+>;
+
+/**
+ * Typed express error handler / request handler union type.
+ */
+type DocRequestHandlerParams<
+  Doc extends RequiredDoc,
+  Path extends DocPathTemplate<Doc>,
+  Method extends keyof Doc['paths'][Path],
+> = core.RequestHandlerParams<
+  PathSchema<Doc, Path, Method>,
+  ResponseBodyToJsonSchema<Doc, Path, Method>,
+  RequestBodyToJsonSchema<Doc, Path, Method>,
+  QuerySchema<Doc, Path, Method>,
+  Record<string, string>
+>;
+
+/**
+ * Superset of the express router path matcher that enforces typed request and response bodies.
+ */
+export interface DocRequestMatcher<
+  Doc extends RequiredDoc,
+  T,
+  Method extends
+    | 'all'
+    | 'get'
+    | 'post'
+    | 'put'
+    | 'delete'
+    | 'patch'
+    | 'options'
+    | 'head',
+> {
+  <Path extends MethodAwareDocPath<Doc, DocPathTemplate<Doc>, Method>>(
+    path: Path,
+    ...handlers: Array<DocRequestHandler<Doc, Path, Method>>
+  ): T;
+  <Path extends MethodAwareDocPath<Doc, DocPathTemplate<Doc>, Method>>(
+    path: Path,
+    ...handlers: Array<DocRequestHandlerParams<Doc, Path, Method>>
+  ): T;
+}
@@ -0,0 +1,91 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import type {
+  ContentObject,
+  OpenAPIObject,
+  ReferenceObject,
+  RequestBodyObject,
+  ParameterObject,
+  SchemaObject,
+  ResponseObject,
+} from 'openapi3-ts';
+
+/**
+ * This file is meant to hold Immutable overwrites of the values provided by the `openapi3-ts`
+ *  package due to issues with `as const` supporting only readonly values.
+ */
+
+/**
+ * From {@link https://github.com/microsoft/TypeScript/issues/13923#issuecomment-653675557}, allows
+ *  us to convert from `as const` to the various OpenAPI types documented in `openapi3-ts`.
+ */
+export type Immutable<T> = T extends
+  | Function
+  | boolean
+  | number
+  | string
+  | null
+  | undefined
+  ? T
+  : T extends Map<infer K, infer V>
+  ? ReadonlyMap<Immutable<K>, Immutable<V>>
+  : T extends Set<infer S>
+  ? ReadonlySet<Immutable<S>>
+  : { readonly [P in keyof T]: Immutable<T[P]> };
+
+export type ImmutableObject<T> = { readonly [K in keyof T]: Immutable<T[K]> };
+
+export type ImmutableReferenceObject = ImmutableObject<ReferenceObject>;
+
+export type ImmutableOpenAPIObject = ImmutableObject<OpenAPIObject>;
+
+export type ImmutableContentObject = ImmutableObject<ContentObject>;
+
+export type ImmutableRequestBodyObject = ImmutableObject<RequestBodyObject>;
+
+export type ImmutableResponseObject = ImmutableObject<ResponseObject>;
+
+export type ImmutableParameterObject = ImmutableObject<ParameterObject>;
+
+interface HeaderObject extends ParameterObject {
+  in: 'header';
+  style: 'simple';
+}
+
+export type ImmutableHeaderObject = ImmutableObject<HeaderObject>;
+
+interface CookieObject extends ParameterObject {
+  in: 'cookie';
+  style?: 'form';
+}
+
+export type ImmutableCookieObject = ImmutableObject<CookieObject>;
+
+interface QueryObject extends ParameterObject {
+  in: 'query';
+  style?: 'form' | 'deepObject' | 'pipeDelimited' | 'spaceDelimited';
+}
+
+export type ImmutableQueryObject = ImmutableObject<QueryObject>;
+
+interface PathObject extends ParameterObject {
+  in: 'path';
+  style?: 'simple' | 'label' | 'matrix';
+}
+
+export type ImmutablePathObject = ImmutableObject<PathObject>;
+
+export type ImmutableSchemaObject = ImmutableObject<SchemaObject>;
@@ -0,0 +1,45 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import type { RequiredDoc } from './common';
+import type { DocRequestMatcher } from './express';
+
+/**
+ * @public
+ */
+export namespace core {
+  /**
+   * @internal
+   */
+  export type Spec = RequiredDoc;
+
+  /**
+   * @internal
+   */
+  export type RequestMatcher<
+    Doc extends RequiredDoc,
+    T,
+    Method extends
+      | 'all'
+      | 'get'
+      | 'post'
+      | 'put'
+      | 'delete'
+      | 'patch'
+      | 'options'
+      | 'head',
+  > = DocRequestMatcher<Doc, T, Method>;
+}
@@ -0,0 +1,141 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  ImmutableCookieObject,
+  ImmutableHeaderObject,
+  ImmutableParameterObject,
+  ImmutablePathObject,
+  ImmutableQueryObject,
+  ImmutableReferenceObject,
+  ImmutableSchemaObject,
+} from './immutable';
+import {
+  ComponentRef,
+  ComponentTypes,
+  DocOperation,
+  DocPath,
+  DocPathMethod,
+  Filter,
+  FullMap,
+  MapDiscriminatedUnion,
+  PathTemplate,
+  RequiredDoc,
+} from './common';
+import { FromSchema, JSONSchema7 } from 'json-schema-to-ts';
+
+type DocParameter<
+  Doc extends RequiredDoc,
+  Path extends Extract<keyof Doc['paths'], string>,
+  Method extends keyof Doc['paths'][Path],
+  Parameter extends keyof Doc['paths'][Path][Method]['parameters'],
+> = DocOperation<
+  Doc,
+  Path,
+  Method
+>['parameters'][Parameter] extends ImmutableReferenceObject
+  ? 'parameters' extends ComponentTypes<Doc>
+    ? ComponentRef<
+        Doc,
+        'parameters',
+        DocOperation<Doc, Path, Method>['parameters'][Parameter]
+      >
+    : never
+  : DocOperation<Doc, Path, Method>['parameters'][Parameter];
+
+type DocParameters<
+  Doc extends RequiredDoc,
+  Path extends Extract<keyof Doc['paths'], string>,
+  Method extends keyof Doc['paths'][Path],
+> = DocOperation<Doc, Path, Method>['parameters'] extends ReadonlyArray<any>
+  ? {
+      [Index in keyof DocOperation<
+        Doc,
+        Path,
+        Method
+      >['parameters']]: DocParameter<Doc, Path, Method, Index>;
+    }
+  : never;
+
+type ResolveDocParameterSchema<
+  Doc extends RequiredDoc,
+  Schema extends ImmutableParameterObject['schema'],
+> = Schema extends ImmutableReferenceObject
+  ? 'parameters' extends ComponentTypes<Doc>
+    ? ComponentRef<Doc, 'parameters', Schema>
+    : never
+  : Schema;
+
+type ParameterSchema<
+  Doc extends RequiredDoc,
+  Schema extends ImmutableParameterObject['schema'],
+> = ResolveDocParameterSchema<Doc, Schema> extends infer R
+  ? R extends ImmutableSchemaObject
+    ? R extends JSONSchema7
+      ? FromSchema<R>
+      : never
+    : never
+  : never;
+
+type MapToSchema<
+  Doc extends RequiredDoc,
+  T extends Record<string, ImmutableParameterObject>,
+> = {
+  [V in keyof T]: NonNullable<T[V]> extends ImmutableParameterObject
+    ? ParameterSchema<Doc, NonNullable<T[V]>['schema']>
+    : never;
+};
+
+type ParametersSchema<
+  Doc extends RequiredDoc,
+  Path extends Extract<keyof Doc['paths'], string>,
+  Method extends keyof Doc['paths'][Path],
+  FilterType extends ImmutableParameterObject,
+> = number extends keyof DocParameters<Doc, Path, Method>
+  ? MapToSchema<
+      Doc,
+      FullMap<
+        MapDiscriminatedUnion<
+          Filter<DocParameters<Doc, Path, Method>[number], FilterType>,
+          'name'
+        >
+      >
+    >
+  : never;
+
+export type HeaderSchema<
+  Doc extends RequiredDoc,
+  Path extends PathTemplate<Extract<keyof Doc['paths'], string>>,
+  Method extends DocPathMethod<Doc, Path>,
+> = ParametersSchema<Doc, DocPath<Doc, Path>, Method, ImmutableHeaderObject>;
+
+export type CookieSchema<
+  Doc extends RequiredDoc,
+  Path extends PathTemplate<Extract<keyof Doc['paths'], string>>,
+  Method extends DocPathMethod<Doc, Path>,
+> = ParametersSchema<Doc, DocPath<Doc, Path>, Method, ImmutableCookieObject>;
+
+export type PathSchema<
+  Doc extends RequiredDoc,
+  Path extends PathTemplate<Extract<keyof Doc['paths'], string>>,
+  Method extends DocPathMethod<Doc, Path>,
+> = ParametersSchema<Doc, DocPath<Doc, Path>, Method, ImmutablePathObject>;
+
+export type QuerySchema<
+  Doc extends RequiredDoc,
+  Path extends PathTemplate<Extract<keyof Doc['paths'], string>>,
+  Method extends DocPathMethod<Doc, Path>,
+> = ParametersSchema<Doc, DocPath<Doc, Path>, Method, ImmutableQueryObject>;
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Pulled from https://github.com/varanauskas/oatx.
+ */
+
+import type {
+  ComponentRef,
+  ComponentTypes,
+  ObjectWithContentSchema,
+  RequiredDoc,
+  DocOperation,
+  DocPath,
+  DocPathMethod,
+  DocPathTemplate,
+  PathTemplate,
+  ToTypeSafe,
+} from './common';
+import {
+  ImmutableReferenceObject,
+  ImmutableRequestBodyObject,
+} from './immutable';
+
+type RequestBody<
+  Doc extends RequiredDoc,
+  Path extends Extract<keyof Doc['paths'], string>,
+  Method extends keyof Doc['paths'][Path],
+> = DocOperation<
+  Doc,
+  Path,
+  Method
+>['requestBody'] extends ImmutableReferenceObject
+  ? 'requestBodies' extends ComponentTypes<Doc>
+    ? ComponentRef<
+        Doc,
+        'requestBodies',
+        DocOperation<Doc, Path, Method>['requestBody']
+      >
+    : never
+  : DocOperation<Doc, Path, Method>['requestBody'];
+
+type RequestBodySchema<
+  Doc extends RequiredDoc,
+  Path extends DocPathTemplate<Doc>,
+  Method extends DocPathMethod<Doc, Path>,
+> = RequestBody<
+  Doc,
+  DocPath<Doc, Path>,
+  Method
+> extends ImmutableRequestBodyObject
+  ? ObjectWithContentSchema<Doc, RequestBody<Doc, DocPath<Doc, Path>, Method>>
+  : never;
+
+/**
+ * Transform the OpenAPI request body schema to a typesafe JSON schema.
+ */
+export type RequestBodyToJsonSchema<
+  Doc extends RequiredDoc,
+  Path extends PathTemplate<Extract<keyof Doc['paths'], string>>,
+  Method extends DocPathMethod<Doc, Path>,
+> = ToTypeSafe<RequestBodySchema<Doc, Path, Method>>;
@@ -0,0 +1,97 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Pulled from https://github.com/varanauskas/oatx.
+ */
+
+import type {
+  ComponentRef,
+  ComponentTypes,
+  ObjectWithContentSchema,
+  RequiredDoc,
+  DocOperation,
+  DocPath,
+  DocPathMethod,
+  DocPathTemplate,
+  PathTemplate,
+  ToTypeSafe,
+  ValueOf,
+} from './common';
+import { ImmutableReferenceObject, ImmutableResponseObject } from './immutable';
+
+type Response<
+  Doc extends RequiredDoc,
+  Path extends keyof Doc['paths'],
+  Method extends keyof Doc['paths'][Path],
+  StatusCode extends keyof Doc['paths'][Path]['responses'],
+> = DocOperation<
+  Doc,
+  Path,
+  Method
+>['responses'][StatusCode] extends ImmutableReferenceObject
+  ? 'responses' extends ComponentTypes<Doc>
+    ? ComponentRef<
+        Doc,
+        'responses',
+        DocOperation<Doc, Path, Method>['responses'][StatusCode]
+      >
+    : never
+  : DocOperation<Doc, Path, Method>['responses'][StatusCode];
+
+type Responses<
+  Doc extends RequiredDoc,
+  Path extends keyof Doc['paths'],
+  Method extends keyof Doc['paths'][Path],
+> = {
+  [StatusCode in keyof DocOperation<Doc, Path, Method>['responses']]: Response<
+    Doc,
+    Path,
+    Method,
+    StatusCode
+  >;
+};
+
+type ResponseSchema<
+  Doc extends RequiredDoc,
+  Object extends ImmutableResponseObject,
+> = ObjectWithContentSchema<Doc, Object>;
+
+type ResponseSchemas<
+  Doc extends RequiredDoc,
+  Path extends DocPathTemplate<Doc>,
+  Method extends DocPathMethod<Doc, Path>,
+> = {
+  [StatusCode in keyof Responses<Doc, DocPath<Doc, Path>, Method>]: Responses<
+    Doc,
+    DocPath<Doc, Path>,
+    Method
+  >[StatusCode] extends ImmutableResponseObject
+    ? ResponseSchema<
+        Doc,
+        Responses<Doc, DocPath<Doc, Path>, Method>[StatusCode]
+      >
+    : never;
+};
+
+/**
+ * Transform the OpenAPI request body schema to a typesafe JSON schema.
+ */
+export type ResponseBodyToJsonSchema<
+  Doc extends RequiredDoc,
+  Path extends PathTemplate<Extract<keyof Doc['paths'], string>>,
+  Method extends DocPathMethod<Doc, Path>,
+> = ToTypeSafe<ValueOf<ResponseSchemas<Doc, Path, Method>>>;