feat: typescript-express server template (#324)

introduces a second server template, `typescript-express`

**Tasks**
- [x] Template
- [x] Runtime
- [x] Integration tests
- [x] Existing E2E tests
- [x] Additional E2E tests
- [x] Documentation
- [x] Review

**Why Express**
`express` is one of the most popular server frameworks for NodeJS,
getting approximately 10x as many weekly downloads as `koa`

Its also quite similar to `koa` making it a good candidate for the
second server template.

This makes it somewhat less interesting to implement, compared to other
options like `nextjs` (#152) but also means that its a good way to
prompt refactors like #316 without requiring a bunch of new
functionality.

**Runtime**
It's clear at this point that there is a lot of duplicated code between
all the runtimes. I like keeping the separate runtime packages for
several reasons:
- Dependency declaration / management is cleaner
- NPM download trends can function as a rough proxy for adoption / usage
_(although private caching registries cause this to under-report
significantly)_

It probably makes sense to introduce a `typescript-runtime-common`
package soon.

**Approach**
The approach ends up looking near identical to the `typescript-koa`
template, in terms of the end developer experience. This is particularly
reinforced by the E2E tests and how little difference exists between the
two implementations.

Author: mnahkies

README.md

@@ -9,7 +9,7 @@ and API server scaffolding (routing, validation, serialization) from api specifi
 Currently, [OpenAPI 3.0](https://swagger.io/specification/v3), [OpenAPI 3.1](https://swagger.io/specification/),
 and [TypeSpec](https://typespec.io/) are supported as input specifications.
 
-With typescript templates for [koa](https://openapi-code-generator.nahkies.co.nz/guides/server-templates/typescript-koa), [fetch](https://openapi-code-generator.nahkies.co.nz/guides/client-templates/typescript-fetch), [axios](https://openapi-code-generator.nahkies.co.nz/guides/client-templates/typescript-axios), and [angular](https://openapi-code-generator.nahkies.co.nz/guides/client-templates/typescript-angular) currently available.
+With typescript templates for [koa](https://openapi-code-generator.nahkies.co.nz/guides/server-templates/typescript-koa), [express](https://openapi-code-generator.nahkies.co.nz/guides/server-templates/typescript-express), [fetch](https://openapi-code-generator.nahkies.co.nz/guides/client-templates/typescript-fetch), [axios](https://openapi-code-generator.nahkies.co.nz/guides/client-templates/typescript-axios), and [angular](https://openapi-code-generator.nahkies.co.nz/guides/client-templates/typescript-angular) currently available.
 
 The [fetch](https://openapi-code-generator.nahkies.co.nz/guides/client-templates/typescript-fetch) and [axios](https://openapi-code-generator.nahkies.co.nz/guides/client-templates/typescript-axios) templates work great in conjunction with [react-query](https://tanstack.com/query/latest)
 
@@ -39,6 +39,7 @@ The repository is structured as a mono repo of several npm packages that work to
 
 - [openapi-code-generator](./packages/openapi-code-generator)
 - [typescript-axios-runtime](./packages/typescript-axios-runtime)
+- [typescript-express-runtime](./packages/typescript-express-runtime)
 - [typescript-fetch-runtime](./packages/typescript-fetch-runtime)
 - [typescript-koa-runtime](./packages/typescript-koa-runtime)
 

e2e/scripts/generate.sh

@@ -12,6 +12,14 @@ yarn openapi-code-generator \
   --extract-inline-schemas \
   --grouping-strategy first-tag
 
+yarn openapi-code-generator \
+  --input ./openapi.yaml \
+  --output ./src/generated/server/express \
+  --template typescript-express \
+  --schema-builder "$SCHEMA_BUILDER" \
+  --extract-inline-schemas \
+  --grouping-strategy first-tag
+
 yarn openapi-code-generator \
   --input ./openapi.yaml \
   --output ./src/generated/client/fetch \

e2e/src/express.entrypoint.ts

@@ -0,0 +1,57 @@
+import {type NextFunction, type Request, type Response, Router} from "express"
+import {bootstrap} from "./generated/server/express"
+import {createEscapeHatchesRouter} from "./routes/express/escape-hatches"
+import {createRequestHeadersRouter} from "./routes/express/request-headers"
+import {createValidationRouter} from "./routes/express/validation"
+import {createErrorResponse} from "./shared"
+
+function createRouter() {
+  const router = Router()
+
+  const requestHeadersRouter = createRequestHeadersRouter()
+  const validationRouter = createValidationRouter()
+  const escapeHatchesRouter = createEscapeHatchesRouter()
+
+  router.use(requestHeadersRouter)
+  router.use(validationRouter)
+  router.use(escapeHatchesRouter)
+
+  return router
+}
+
+export async function startExpressServer() {
+  const {app, server, address} = await bootstrap({
+    cors: {
+      credentials: true,
+      allowedHeaders: ["Authorization", "Content-Type"],
+      methods: ["GET", "OPTIONS"],
+      origin: "http://example.com",
+    },
+    router: createRouter(),
+    notFoundHandler: (req: Request, res: Response, next: NextFunction) => {
+      res.status(404).json({code: 404, message: "route not found"})
+    },
+    errorHandler: (
+      err: Error,
+      req: Request,
+      res: Response,
+      next: NextFunction,
+    ) => {
+      if (res.headersSent) {
+        return next(err)
+      }
+
+      const {status, body} = createErrorResponse(err)
+      res.status(status).json(body)
+    },
+  })
+
+  return {app, server, address}
+}
+
+if (require.main === module) {
+  startExpressServer().catch((err) => {
+    console.error("fatal error", err)
+    process.exit(1)
+  })
+}